diff options
Diffstat (limited to 'theories')
35 files changed, 8222 insertions, 2865 deletions
diff --git a/theories/Init/Decimal.v b/theories/Init/Decimal.v index 10c3baa2cd..855db8bc3f 100644 --- a/theories/Init/Decimal.v +++ b/theories/Init/Decimal.v @@ -156,6 +156,37 @@ Definition nztail_int d := | Neg d => let (r, n) := nztail d in pair (Neg r) n end. +(** [del_head n d] removes [n] digits at beginning of [d] + or returns [zero] if [d] has less than [n] digits. *) + +Fixpoint del_head n d := + match n with + | O => d + | S n => + match d with + | Nil => zero + | D0 d | D1 d | D2 d | D3 d | D4 d | D5 d | D6 d | D7 d | D8 d | D9 d => + del_head n d + end + end. + +Definition del_head_int n d := + match d with + | Pos d => Pos (del_head n d) + | Neg d => Neg (del_head n d) + end. + +(** [del_tail n d] removes [n] digits at end of [d] + or returns [zero] if [d] has less than [n] digits. *) + +Fixpoint del_tail n d := rev (del_head n (rev d)). + +Definition del_tail_int n d := + match d with + | Pos d => Pos (del_tail n d) + | Neg d => Neg (del_tail n d) + end. + Module Little. (** Successor of little-endian numbers *) diff --git a/theories/Init/Prelude.v b/theories/Init/Prelude.v index 6126d9c37d..71ba3e645d 100644 --- a/theories/Init/Prelude.v +++ b/theories/Init/Prelude.v @@ -43,5 +43,5 @@ Numeral Notation nat Nat.of_uint Nat.to_uint : nat_scope (abstract after 5001). (* Printing/Parsing of bytes *) Export Byte.ByteSyntaxNotations. -(* Default substrings not considered by queries like SearchAbout *) +(* Default substrings not considered by queries like Search *) Add Search Blacklist "_subproof" "_subterm" "Private_". diff --git a/theories/NArith/BinNat.v b/theories/NArith/BinNat.v index f0011fe147..d68c32b371 100644 --- a/theories/NArith/BinNat.v +++ b/theories/NArith/BinNat.v @@ -943,6 +943,64 @@ Proof. destruct p; simpl; trivial. Qed. +(** ** Properties of [iter] *) + +Lemma iter_swap_gen : forall A B (f:A -> B) (g:A -> A) (h:B -> B), + (forall a, f (g a) = h (f a)) -> forall n a, + f (iter n g a) = iter n h (f a). +Proof. + destruct n; simpl; intros; rewrite ?H; trivial. + now apply Pos.iter_swap_gen. +Qed. + +Theorem iter_swap : + forall n (A:Type) (f:A -> A) (x:A), + iter n f (f x) = f (iter n f x). +Proof. + intros. symmetry. now apply iter_swap_gen. +Qed. + +Theorem iter_succ : + forall n (A:Type) (f:A -> A) (x:A), + iter (succ n) f x = f (iter n f x). +Proof. + destruct n; intros; simpl; trivial. + now apply Pos.iter_succ. +Qed. + +Theorem iter_succ_r : + forall n (A:Type) (f:A -> A) (x:A), + iter (succ n) f x = iter n f (f x). +Proof. + intros; now rewrite iter_succ, iter_swap. +Qed. + +Theorem iter_add : + forall p q (A:Type) (f:A -> A) (x:A), + iter (p+q) f x = iter p f (iter q f x). +Proof. + induction p using peano_ind; intros; trivial. + now rewrite add_succ_l, !iter_succ, IHp. +Qed. + +Theorem iter_ind : + forall (A:Type) (f:A -> A) (a:A) (P:N -> A -> Prop), + P 0 a -> + (forall n a', P n a' -> P (succ n) (f a')) -> + forall n, P n (iter n f a). +Proof. + induction n using peano_ind; trivial. + rewrite iter_succ; auto. +Qed. + +Theorem iter_invariant : + forall (n:N) (A:Type) (f:A -> A) (Inv:A -> Prop), + (forall x:A, Inv x -> Inv (f x)) -> + forall x:A, Inv x -> Inv (iter n f x). +Proof. + intros; apply iter_ind with (P := fun _ => Inv); trivial. +Qed. + End N. Bind Scope N_scope with N.t N. diff --git a/theories/Numbers/Cyclic/Int31/Cyclic31.v b/theories/Numbers/Cyclic/Int31/Cyclic31.v index 1c790a37a0..f6b2544b6e 100644 --- a/theories/Numbers/Cyclic/Int31/Cyclic31.v +++ b/theories/Numbers/Cyclic/Int31/Cyclic31.v @@ -2226,7 +2226,7 @@ Section Int31_Specs. < ([|iter312_sqrt n rec ih il j|] + 1) ^ 2. Proof. revert rec ih il j; elim n; unfold iter312_sqrt; fold iter312_sqrt; clear n. - intros rec ih il j Hi Hj Hij Hrec; apply sqrt312_step_correct; auto with zarith. + intros rec ih il j Hi Hj Hij Hrec; apply sqrt312_step_correct. 1-3: lia. intros; apply Hrec. 2: rewrite Z.pow_0_r. 1-3: lia. intros n Hrec rec ih il j Hi Hj Hij HHrec. apply sqrt312_step_correct; auto. diff --git a/theories/Numbers/Cyclic/Int63/Int63.v b/theories/Numbers/Cyclic/Int63/Int63.v index ca50470edc..bacc4a7650 100644 --- a/theories/Numbers/Cyclic/Int63/Int63.v +++ b/theories/Numbers/Cyclic/Int63/Int63.v @@ -1316,9 +1316,8 @@ Lemma iter_sqrt_correct n rec i j: 0 < φ i -> 0 < φ j -> φ (iter_sqrt n rec i j) ^ 2 <= φ i < (φ (iter_sqrt n rec i j) + 1) ^ 2. Proof. revert rec i j; elim n; unfold iter_sqrt; fold iter_sqrt; clear n. - intros rec i j Hi Hj Hij H31 Hrec; apply sqrt_step_correct; auto with zarith. - intros; apply Hrec; auto with zarith. - rewrite Zpower_0_r; auto with zarith. + intros rec i j Hi Hj Hij H31 Hrec; apply sqrt_step_correct. 1-4: lia. + intros; apply Hrec; only 2: rewrite Zpower_0_r; auto with zarith. intros n Hrec rec i j Hi Hj Hij H31 HHrec. apply sqrt_step_correct; auto. intros j1 Hj1 Hjp1; apply Hrec; auto with zarith. @@ -1516,9 +1515,8 @@ Lemma iter2_sqrt_correct n rec ih il j: < (φ (iter2_sqrt n rec ih il j) + 1) ^ 2. Proof. revert rec ih il j; elim n; unfold iter2_sqrt; fold iter2_sqrt; clear n. - intros rec ih il j Hi Hj Hij Hrec; apply sqrt2_step_correct; auto with zarith. - intros; apply Hrec; auto with zarith. - rewrite Zpower_0_r; auto with zarith. + intros rec ih il j Hi Hj Hij Hrec; apply sqrt2_step_correct. 1-3: lia. + intros; apply Hrec; only 2: rewrite Zpower_0_r; auto with zarith. intros n Hrec rec ih il j Hi Hj Hij HHrec. apply sqrt2_step_correct; auto. intros j1 Hj1 Hjp1; apply Hrec; auto with zarith. diff --git a/theories/PArith/BinPos.v b/theories/PArith/BinPos.v index 99e77fd596..387ab75362 100644 --- a/theories/PArith/BinPos.v +++ b/theories/PArith/BinPos.v @@ -597,6 +597,13 @@ Proof. now rewrite !IHp, iter_swap. Qed. +Theorem iter_succ_r : + forall p (A:Type) (f:A -> A) (x:A), + iter f x (succ p) = iter f (f x) p. +Proof. + intros; now rewrite iter_succ, iter_swap. +Qed. + Theorem iter_add : forall p q (A:Type) (f:A -> A) (x:A), iter f x (p+q) = iter f (iter f x q) p. @@ -606,14 +613,22 @@ Proof. now rewrite add_succ_l, !iter_succ, IHp. Qed. +Theorem iter_ind : + forall (A:Type) (f:A -> A) (a:A) (P:positive -> A -> Prop), + P 1 (f a) -> + (forall p a', P p a' -> P (succ p) (f a')) -> + forall p, P p (iter f a p). +Proof. + induction p using peano_ind; trivial. + rewrite iter_succ; auto. +Qed. + Theorem iter_invariant : forall (p:positive) (A:Type) (f:A -> A) (Inv:A -> Prop), (forall x:A, Inv x -> Inv (f x)) -> forall x:A, Inv x -> Inv (iter f x p). Proof. - induction p as [p IHp|p IHp|]; simpl; trivial. - intros A f Inv H x H0. apply H, IHp, IHp; trivial. - intros A f Inv H x H0. apply IHp, IHp; trivial. + intros; apply iter_ind with (P := fun _ => Inv); auto. Qed. (** ** Properties of power *) diff --git a/theories/QArith/QArith_base.v b/theories/QArith/QArith_base.v index a7f338aec3..bd5225d9ef 100644 --- a/theories/QArith/QArith_base.v +++ b/theories/QArith/QArith_base.v @@ -44,13 +44,39 @@ Definition of_decimal (d:Decimal.decimal) : Q := end. Definition to_decimal (q:Q) : option Decimal.decimal := + (* choose between 123e-2 and 1.23, this is purely heuristic + and doesn't play any soundness role *) + let choose_exponent i ne := + let i := match i with Decimal.Pos i | Decimal.Neg i => i end in + let li := Decimal.nb_digits i in + let le := Decimal.nb_digits (Nat.to_uint ne) in + Nat.ltb (Nat.add li le) ne in + (* print 123 / 100 as 123e-2 *) + let decimal_exponent i ne := + let e := Z.to_int (Z.opp (Z.of_nat ne)) in + Decimal.DecimalExp i Decimal.Nil e in + (* print 123 / 100 as 1.23 *) + let decimal_dot i ne := + let ai := match i with Decimal.Pos i | Decimal.Neg i => i end in + let ni := Decimal.nb_digits ai in + if Nat.ltb ne ni then + let i := Decimal.del_tail_int ne i in + let f := Decimal.del_head (Nat.sub ni ne) ai in + Decimal.Decimal i f + else + let z := match i with + | Decimal.Pos _ => Decimal.Pos (Decimal.zero) + | Decimal.Neg _ => Decimal.Neg (Decimal.zero) end in + Decimal.Decimal z (Nat.iter (Nat.sub ne ni) Decimal.D0 ai) in let num := Z.to_int (Qnum q) in let (den, e_den) := Decimal.nztail (Pos.to_uint (Qden q)) in match den with | Decimal.D1 Decimal.Nil => - match Z.of_nat e_den with - | Z0 => Some (Decimal.Decimal num Decimal.Nil) - | e => Some (Decimal.DecimalExp num Decimal.Nil (Z.to_int (Z.opp e))) + match e_den with + | O => Some (Decimal.Decimal num Decimal.Nil) + | ne => + if choose_exponent num ne then Some (decimal_exponent num ne) + else Some (decimal_dot num ne) end | _ => None end. diff --git a/theories/Reals/Abstract/ConstructiveAbs.v b/theories/Reals/Abstract/ConstructiveAbs.v new file mode 100644 index 0000000000..d357ad2d54 --- /dev/null +++ b/theories/Reals/Abstract/ConstructiveAbs.v @@ -0,0 +1,950 @@ +(************************************************************************) +(* * The Coq Proof Assistant / The Coq Development Team *) +(* v * INRIA, CNRS and contributors - Copyright 1999-2019 *) +(* <O___,, * (see CREDITS file for the list of authors) *) +(* \VV/ **************************************************************) +(* // * This file is distributed under the terms of the *) +(* * GNU Lesser General Public License Version 2.1 *) +(* * (see LICENSE file for the text of the license) *) +(************************************************************************) +(************************************************************************) + +Require Import QArith. +Require Import Qabs. +Require Import ConstructiveReals. + +Local Open Scope ConstructiveReals. + +(** Properties of constructive absolute value (defined in + ConstructiveReals.CRabs). + Definition of minimum, maximum and their properties. *) + +Instance CRabs_morph + : forall {R : ConstructiveReals}, + CMorphisms.Proper + (CMorphisms.respectful (CReq R) (CReq R)) (CRabs R). +Proof. + intros R x y [H H0]. split. + - rewrite <- CRabs_def. split. + + apply (CRle_trans _ x). apply H. + pose proof (CRabs_def R x (CRabs R x)) as [_ H1]. + apply H1. apply CRle_refl. + + apply (CRle_trans _ (CRopp R x)). intro abs. + apply CRopp_lt_cancel in abs. contradiction. + pose proof (CRabs_def R x (CRabs R x)) as [_ H1]. + apply H1. apply CRle_refl. + - rewrite <- CRabs_def. split. + + apply (CRle_trans _ y). apply H0. + pose proof (CRabs_def R y (CRabs R y)) as [_ H1]. + apply H1. apply CRle_refl. + + apply (CRle_trans _ (CRopp R y)). intro abs. + apply CRopp_lt_cancel in abs. contradiction. + pose proof (CRabs_def R y (CRabs R y)) as [_ H1]. + apply H1. apply CRle_refl. +Qed. + +Add Parametric Morphism {R : ConstructiveReals} : (CRabs R) + with signature CReq R ==> CReq R + as CRabs_morph_prop. +Proof. + intros. apply CRabs_morph, H. +Qed. + +Lemma CRabs_right : forall {R : ConstructiveReals} (x : CRcarrier R), + 0 <= x -> CRabs R x == x. +Proof. + intros. split. + - pose proof (CRabs_def R x (CRabs R x)) as [_ H1]. + apply H1, CRle_refl. + - rewrite <- CRabs_def. split. apply CRle_refl. + apply (CRle_trans _ (CRzero R)). 2: exact H. + apply (CRle_trans _ (CRopp R (CRzero R))). + intro abs. apply CRopp_lt_cancel in abs. contradiction. + apply (CRplus_le_reg_l (CRzero R)). + apply (CRle_trans _ (CRzero R)). apply CRplus_opp_r. + apply CRplus_0_r. +Qed. + +Lemma CRabs_opp : forall {R : ConstructiveReals} (x : CRcarrier R), + CRabs R (- x) == CRabs R x. +Proof. + intros. split. + - rewrite <- CRabs_def. split. + + pose proof (CRabs_def R (CRopp R x) (CRabs R (CRopp R x))) as [_ H1]. + specialize (H1 (CRle_refl (CRabs R (CRopp R x)))) as [_ H1]. + apply (CRle_trans _ (CRopp R (CRopp R x))). + 2: exact H1. apply (CRopp_involutive x). + + pose proof (CRabs_def R (CRopp R x) (CRabs R (CRopp R x))) as [_ H1]. + apply H1, CRle_refl. + - rewrite <- CRabs_def. split. + + pose proof (CRabs_def R x (CRabs R x)) as [_ H1]. + apply H1, CRle_refl. + + apply (CRle_trans _ x). apply CRopp_involutive. + pose proof (CRabs_def R x (CRabs R x)) as [_ H1]. + apply H1, CRle_refl. +Qed. + +Lemma CRabs_minus_sym : forall {R : ConstructiveReals} (x y : CRcarrier R), + CRabs R (x - y) == CRabs R (y - x). +Proof. + intros R x y. setoid_replace (x - y) with (-(y-x)). + rewrite CRabs_opp. reflexivity. unfold CRminus. + rewrite CRopp_plus_distr, CRplus_comm, CRopp_involutive. + reflexivity. +Qed. + +Lemma CRabs_left : forall {R : ConstructiveReals} (x : CRcarrier R), + x <= 0 -> CRabs R x == - x. +Proof. + intros. rewrite <- CRabs_opp. apply CRabs_right. + rewrite <- CRopp_0. apply CRopp_ge_le_contravar, H. +Qed. + +Lemma CRabs_triang : forall {R : ConstructiveReals} (x y : CRcarrier R), + CRabs R (x + y) <= CRabs R x + CRabs R y. +Proof. + intros. rewrite <- CRabs_def. split. + - apply (CRle_trans _ (CRplus R (CRabs R x) y)). + apply CRplus_le_compat_r. + pose proof (CRabs_def R x (CRabs R x)) as [_ H1]. + apply H1, CRle_refl. + apply CRplus_le_compat_l. + pose proof (CRabs_def R y (CRabs R y)) as [_ H1]. + apply H1, CRle_refl. + - apply (CRle_trans _ (CRplus R (CRopp R x) (CRopp R y))). + apply CRopp_plus_distr. + apply (CRle_trans _ (CRplus R (CRabs R x) (CRopp R y))). + apply CRplus_le_compat_r. + pose proof (CRabs_def R x (CRabs R x)) as [_ H1]. + apply H1, CRle_refl. + apply CRplus_le_compat_l. + pose proof (CRabs_def R y (CRabs R y)) as [_ H1]. + apply H1, CRle_refl. +Qed. + +Lemma CRabs_le : forall {R : ConstructiveReals} (a b:CRcarrier R), + (-b <= a /\ a <= b) -> CRabs R a <= b. +Proof. + intros. pose proof (CRabs_def R a b) as [H0 _]. + apply H0. split. apply H. destruct H. + rewrite <- (CRopp_involutive b). + apply CRopp_ge_le_contravar. exact H. +Qed. + +Lemma CRabs_triang_inv : forall {R : ConstructiveReals} (x y : CRcarrier R), + CRabs R x - CRabs R y <= CRabs R (x - y). +Proof. + intros. apply (CRplus_le_reg_r (CRabs R y)). + unfold CRminus. rewrite CRplus_assoc, CRplus_opp_l. + rewrite CRplus_0_r. + apply (CRle_trans _ (CRabs R (x - y + y))). + setoid_replace (x - y + y) with x. apply CRle_refl. + unfold CRminus. rewrite CRplus_assoc, CRplus_opp_l. + rewrite CRplus_0_r. reflexivity. + apply CRabs_triang. +Qed. + +Lemma CRabs_triang_inv2 : forall {R : ConstructiveReals} (x y : CRcarrier R), + CRabs R (CRabs R x - CRabs R y) <= CRabs R (x - y). +Proof. + intros. apply CRabs_le. split. + 2: apply CRabs_triang_inv. + apply (CRplus_le_reg_r (CRabs R y)). + unfold CRminus. rewrite CRplus_assoc, CRplus_opp_l. + rewrite CRplus_0_r. fold (x - y). + rewrite CRplus_comm, CRabs_minus_sym. + apply (CRle_trans _ _ _ (CRabs_triang_inv y (y-x))). + setoid_replace (y - (y - x)) with x. apply CRle_refl. + unfold CRminus. rewrite CRopp_plus_distr, <- CRplus_assoc. + rewrite CRplus_opp_r, CRplus_0_l. apply CRopp_involutive. +Qed. + +Lemma CR_of_Q_abs : forall {R : ConstructiveReals} (q : Q), + CRabs R (CR_of_Q R q) == CR_of_Q R (Qabs q). +Proof. + intros. destruct (Qlt_le_dec 0 q). + - apply (CReq_trans _ (CR_of_Q R q)). + apply CRabs_right. apply (CRle_trans _ (CR_of_Q R 0)). + apply CR_of_Q_zero. apply CR_of_Q_le. apply Qlt_le_weak, q0. + apply CR_of_Q_morph. symmetry. apply Qabs_pos, Qlt_le_weak, q0. + - apply (CReq_trans _ (CR_of_Q R (-q))). + apply (CReq_trans _ (CRabs R (CRopp R (CR_of_Q R q)))). + apply CReq_sym, CRabs_opp. + 2: apply CR_of_Q_morph; symmetry; apply Qabs_neg, q0. + apply (CReq_trans _ (CRopp R (CR_of_Q R q))). + 2: apply CReq_sym, CR_of_Q_opp. + apply CRabs_right. apply (CRle_trans _ (CR_of_Q R 0)). + apply CR_of_Q_zero. + apply (CRle_trans _ (CR_of_Q R (-q))). apply CR_of_Q_le. + apply (Qplus_le_l _ _ q). ring_simplify. exact q0. + apply CR_of_Q_opp. +Qed. + +Lemma CRle_abs : forall {R : ConstructiveReals} (x : CRcarrier R), + x <= CRabs R x. +Proof. + intros. pose proof (CRabs_def R x (CRabs R x)) as [_ H]. + apply H, CRle_refl. +Qed. + +Lemma CRabs_pos : forall {R : ConstructiveReals} (x : CRcarrier R), + 0 <= CRabs R x. +Proof. + intros. intro abs. destruct (CRltLinear R). clear p. + specialize (s _ x _ abs). destruct s. + exact (CRle_abs x c). rewrite CRabs_left in abs. + rewrite <- CRopp_0 in abs. apply CRopp_lt_cancel in abs. + exact (CRlt_asym _ _ abs c). apply CRlt_asym, c. +Qed. + +Lemma CRabs_appart_0 : forall {R : ConstructiveReals} (x : CRcarrier R), + 0 < CRabs R x -> x ≶ 0. +Proof. + intros. destruct (CRltLinear R). clear p. + pose proof (s _ x _ H) as [pos|neg]. + right. exact pos. left. + destruct (CR_Q_dense R _ _ neg) as [q [H0 H1]]. + destruct (Qlt_le_dec 0 q). + - destruct (s (CR_of_Q R (-q)) x 0). + rewrite <- CR_of_Q_zero. apply CR_of_Q_lt. + apply (Qplus_lt_l _ _ q). ring_simplify. exact q0. + exfalso. pose proof (CRabs_def R x (CR_of_Q R q)) as [H2 _]. + apply H2. clear H2. split. apply CRlt_asym, H0. + 2: exact H1. rewrite <- Qopp_involutive, CR_of_Q_opp. + apply CRopp_ge_le_contravar, CRlt_asym, c. exact c. + - apply (CRlt_le_trans _ _ _ H0). + rewrite <- CR_of_Q_zero. apply CR_of_Q_le. exact q0. +Qed. + + +(* The proof by cases on the signs of x and y applies constructively, + because of the positivity hypotheses. *) +Lemma CRabs_mult : forall {R : ConstructiveReals} (x y : CRcarrier R), + CRabs R (x * y) == CRabs R x * CRabs R y. +Proof. + intro R. + assert (forall (x y : CRcarrier R), + x ≶ 0 + -> y ≶ 0 + -> CRabs R (x * y) == CRabs R x * CRabs R y) as prep. + { intros. destruct H, H0. + + rewrite CRabs_right, CRabs_left, CRabs_left. + rewrite <- CRopp_mult_distr_l, CRopp_mult_distr_r, CRopp_involutive. + reflexivity. + apply CRlt_asym, c0. apply CRlt_asym, c. + setoid_replace (x*y) with (- x * - y). + apply CRlt_asym, CRmult_lt_0_compat. + rewrite <- CRopp_0. apply CRopp_gt_lt_contravar, c. + rewrite <- CRopp_0. apply CRopp_gt_lt_contravar, c0. + rewrite <- CRopp_mult_distr_l, CRopp_mult_distr_r, CRopp_involutive. + reflexivity. + + rewrite CRabs_left, CRabs_left, CRabs_right. + rewrite <- CRopp_mult_distr_l. reflexivity. + apply CRlt_asym, c0. apply CRlt_asym, c. + rewrite <- (CRmult_0_l y). + apply CRmult_le_compat_r_half. exact c0. + apply CRlt_asym, c. + + rewrite CRabs_left, CRabs_right, CRabs_left. + rewrite <- CRopp_mult_distr_r. reflexivity. + apply CRlt_asym, c0. apply CRlt_asym, c. + rewrite <- (CRmult_0_r x). + apply CRmult_le_compat_l_half. + exact c. apply CRlt_asym, c0. + + rewrite CRabs_right, CRabs_right, CRabs_right. reflexivity. + apply CRlt_asym, c0. apply CRlt_asym, c. + apply CRlt_asym, CRmult_lt_0_compat; assumption. } + split. + - intro abs. + assert (0 < CRabs R x * CRabs R y). + { apply (CRle_lt_trans _ (CRabs R (x*y))). + apply CRabs_pos. exact abs. } + pose proof (CRmult_pos_appart_zero _ _ H). + rewrite CRmult_comm in H. + apply CRmult_pos_appart_zero in H. + destruct H. 2: apply (CRabs_pos y c). + destruct H0. 2: apply (CRabs_pos x c0). + apply CRabs_appart_0 in c. + apply CRabs_appart_0 in c0. + rewrite (prep x y) in abs. + exact (CRlt_asym _ _ abs abs). exact c0. exact c. + - intro abs. + assert (0 < CRabs R (x * y)). + { apply (CRle_lt_trans _ (CRabs R x * CRabs R y)). + rewrite <- (CRmult_0_l (CRabs R y)). + apply CRmult_le_compat_r. + apply CRabs_pos. apply CRabs_pos. exact abs. } + apply CRabs_appart_0 in H. destruct H. + + apply CRopp_gt_lt_contravar in c. + rewrite CRopp_0, CRopp_mult_distr_l in c. + pose proof (CRmult_pos_appart_zero _ _ c). + rewrite CRmult_comm in c. + apply CRmult_pos_appart_zero in c. + rewrite (prep x y) in abs. + exact (CRlt_asym _ _ abs abs). + destruct H. left. apply CRopp_gt_lt_contravar in c0. + rewrite CRopp_involutive, CRopp_0 in c0. exact c0. + right. apply CRopp_gt_lt_contravar in c0. + rewrite CRopp_involutive, CRopp_0 in c0. exact c0. + destruct c. right. exact c. left. exact c. + + pose proof (CRmult_pos_appart_zero _ _ c). + rewrite CRmult_comm in c. + apply CRmult_pos_appart_zero in c. + rewrite (prep x y) in abs. + exact (CRlt_asym _ _ abs abs). + destruct H. right. exact c0. left. exact c0. + destruct c. right. exact c. left. exact c. +Qed. + +Lemma CRabs_lt : forall {R : ConstructiveReals} (x y : CRcarrier R), + CRabs _ x < y -> prod (x < y) (-x < y). +Proof. + split. + - apply (CRle_lt_trans _ _ _ (CRle_abs x)), H. + - apply (CRle_lt_trans _ _ _ (CRle_abs (-x))). + rewrite CRabs_opp. exact H. +Qed. + +Lemma CRabs_def1 : forall {R : ConstructiveReals} (x y : CRcarrier R), + x < y -> -x < y -> CRabs _ x < y. +Proof. + intros. destruct (CRltLinear R), p. + destruct (s x (CRabs R x) y H). 2: exact c0. + rewrite CRabs_left. exact H0. intro abs. + rewrite CRabs_right in c0. exact (CRlt_asym x x c0 c0). + apply CRlt_asym, abs. +Qed. + +Lemma CRabs_def2 : forall {R : ConstructiveReals} (x a:CRcarrier R), + CRabs _ x <= a -> (x <= a) /\ (- a <= x). +Proof. + split. + - exact (CRle_trans _ _ _ (CRle_abs _) H). + - rewrite <- (CRopp_involutive x). + apply CRopp_ge_le_contravar. + rewrite <- CRabs_opp in H. + exact (CRle_trans _ _ _ (CRle_abs _) H). +Qed. + + +(* Minimum *) + +Definition CRmin {R : ConstructiveReals} (x y : CRcarrier R) : CRcarrier R + := (x + y - CRabs _ (y - x)) * CR_of_Q _ (1#2). + +Lemma CRmin_lt_r : forall {R : ConstructiveReals} (x y : CRcarrier R), + CRmin x y < y -> CRmin x y == x. +Proof. + intros. unfold CRmin. unfold CRmin in H. + apply (CRmult_eq_reg_r (CR_of_Q R 2)). + left; apply CR_of_Q_pos; reflexivity. + rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r. + rewrite (CR_of_Q_plus R 1 1), CR_of_Q_one, CRmult_plus_distr_l, CRmult_1_r. + rewrite CRabs_right. unfold CRminus. + rewrite CRopp_plus_distr, CRplus_assoc, <- (CRplus_assoc y). + rewrite CRplus_opp_r, CRplus_0_l, CRopp_involutive. reflexivity. + apply (CRmult_lt_compat_r (CR_of_Q R 2)) in H. + 2: apply CR_of_Q_pos; reflexivity. + rewrite CRmult_assoc, <- CR_of_Q_mult in H. + setoid_replace ((1 # 2) * 2)%Q with 1%Q in H. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r in H. + rewrite CRmult_comm, (CR_of_Q_plus R 1 1), CR_of_Q_one, CRmult_plus_distr_r, + CRmult_1_l in H. + intro abs. rewrite CRabs_left in H. + unfold CRminus in H. + rewrite CRopp_involutive, CRplus_comm in H. + rewrite CRplus_assoc, <- (CRplus_assoc (-x)), CRplus_opp_l in H. + rewrite CRplus_0_l in H. exact (CRlt_asym _ _ H H). + apply CRlt_asym, abs. +Qed. + +Add Parametric Morphism {R : ConstructiveReals} : CRmin + with signature (CReq R) ==> (CReq R) ==> (CReq R) + as CRmin_morph. +Proof. + intros. unfold CRmin. + apply CRmult_morph. 2: reflexivity. + unfold CRminus. + rewrite H, H0. reflexivity. +Qed. + +Instance CRmin_morphT + : forall {R : ConstructiveReals}, + CMorphisms.Proper + (CMorphisms.respectful (CReq R) (CMorphisms.respectful (CReq R) (CReq R))) (@CRmin R). +Proof. + intros R x y H z t H0. + rewrite H, H0. reflexivity. +Qed. + +Lemma CRmin_l : forall {R : ConstructiveReals} (x y : CRcarrier R), + CRmin x y <= x. +Proof. + intros. unfold CRmin. + apply (CRmult_le_reg_r (CR_of_Q R 2)). + rewrite <- CR_of_Q_zero. apply CR_of_Q_lt; reflexivity. + rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r. + rewrite (CR_of_Q_plus _ 1 1), CRmult_plus_distr_l, CR_of_Q_one, CRmult_1_r. + unfold CRminus. rewrite CRplus_assoc. apply CRplus_le_compat_l. + apply (CRplus_le_reg_r (CRabs _ (y + - x)+ -x)). + rewrite CRplus_assoc, <- (CRplus_assoc (-CRabs _ (y + - x))). + rewrite CRplus_opp_l, CRplus_0_l. + rewrite (CRplus_comm x), CRplus_assoc, CRplus_opp_l, CRplus_0_r. + apply CRle_abs. +Qed. + +Lemma CRmin_r : forall {R : ConstructiveReals} (x y : CRcarrier R), + CRmin x y <= y. +Proof. + intros. unfold CRmin. + apply (CRmult_le_reg_r (CR_of_Q R 2)). + rewrite <- CR_of_Q_zero. apply CR_of_Q_lt; reflexivity. + rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r. + rewrite (CR_of_Q_plus _ 1 1), CRmult_plus_distr_l, CR_of_Q_one, CRmult_1_r. + rewrite (CRplus_comm x). + unfold CRminus. rewrite CRplus_assoc. apply CRplus_le_compat_l. + apply (CRplus_le_reg_l (-x)). + rewrite <- CRplus_assoc, CRplus_opp_l, CRplus_0_l. + rewrite <- (CRopp_involutive y), <- CRopp_plus_distr, <- CRopp_plus_distr. + apply CRopp_ge_le_contravar. rewrite CRabs_opp, CRplus_comm. + apply CRle_abs. +Qed. + +Lemma CRnegPartAbsMin : forall {R : ConstructiveReals} (x : CRcarrier R), + CRmin 0 x == (x - CRabs _ x) * (CR_of_Q _ (1#2)). +Proof. + intros. unfold CRmin. unfold CRminus. rewrite CRplus_0_l. + apply CRmult_morph. 2: reflexivity. rewrite CRopp_0, CRplus_0_r. reflexivity. +Qed. + +Lemma CRmin_sym : forall {R : ConstructiveReals} (x y : CRcarrier R), + CRmin x y == CRmin y x. +Proof. + intros. unfold CRmin. apply CRmult_morph. 2: reflexivity. + rewrite CRabs_minus_sym. unfold CRminus. + rewrite (CRplus_comm x y). reflexivity. +Qed. + +Lemma CRmin_mult : + forall {R : ConstructiveReals} (p q r : CRcarrier R), + 0 <= r -> CRmin (r * p) (r * q) == r * CRmin p q. +Proof. + intros R p q r H. unfold CRmin. + setoid_replace (r * q - r * p) with (r * (q - p)). + rewrite CRabs_mult. + rewrite (CRabs_right r). 2: exact H. + rewrite <- CRmult_assoc. apply CRmult_morph. 2: reflexivity. + unfold CRminus. rewrite CRopp_mult_distr_r. + do 2 rewrite <- CRmult_plus_distr_l. reflexivity. + unfold CRminus. rewrite CRopp_mult_distr_r. + rewrite <- CRmult_plus_distr_l. reflexivity. +Qed. + +Lemma CRmin_plus : forall {R : ConstructiveReals} (x y z : CRcarrier R), + x + CRmin y z == CRmin (x + y) (x + z). +Proof. + intros. unfold CRmin. + unfold CRminus. setoid_replace (x + z + - (x + y)) with (z-y). + apply (CRmult_eq_reg_r (CR_of_Q _ 2)). + left. rewrite <- CR_of_Q_zero. apply CR_of_Q_lt; reflexivity. + rewrite CRmult_plus_distr_r. + rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r. + rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r. + rewrite (CR_of_Q_plus _ 1 1), CRmult_plus_distr_l, CR_of_Q_one, CRmult_1_r. + do 3 rewrite (CRplus_assoc x). apply CRplus_morph. reflexivity. + do 2 rewrite <- CRplus_assoc. apply CRplus_morph. 2: reflexivity. + rewrite (CRplus_comm x). apply CRplus_assoc. + rewrite CRopp_plus_distr. rewrite <- CRplus_assoc. + apply CRplus_morph. 2: reflexivity. + rewrite CRplus_comm, <- CRplus_assoc, CRplus_opp_l. + apply CRplus_0_l. +Qed. + +Lemma CRmin_left : forall {R : ConstructiveReals} (x y : CRcarrier R), + x <= y -> CRmin x y == x. +Proof. + intros. unfold CRmin. + apply (CRmult_eq_reg_r (CR_of_Q R 2)). + left. rewrite <- CR_of_Q_zero. apply CR_of_Q_lt; reflexivity. + rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r. + rewrite (CR_of_Q_plus _ 1 1), CRmult_plus_distr_l, CR_of_Q_one, CRmult_1_r. + rewrite CRabs_right. unfold CRminus. rewrite CRopp_plus_distr. + rewrite CRplus_assoc. apply CRplus_morph. reflexivity. + rewrite <- CRplus_assoc, CRplus_opp_r, CRplus_0_l. apply CRopp_involutive. + rewrite <- (CRplus_opp_r x). apply CRplus_le_compat. + exact H. apply CRle_refl. +Qed. + +Lemma CRmin_right : forall {R : ConstructiveReals} (x y : CRcarrier R), + y <= x -> CRmin x y == y. +Proof. + intros. unfold CRmin. + apply (CRmult_eq_reg_r (CR_of_Q R 2)). + left. rewrite <- CR_of_Q_zero. apply CR_of_Q_lt; reflexivity. + rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r. + rewrite (CR_of_Q_plus _ 1 1), CRmult_plus_distr_l, CR_of_Q_one, CRmult_1_r. + rewrite CRabs_left. unfold CRminus. do 2 rewrite CRopp_plus_distr. + rewrite (CRplus_comm x y). + rewrite CRplus_assoc. apply CRplus_morph. reflexivity. + do 2 rewrite CRopp_involutive. + rewrite CRplus_comm, CRplus_assoc, CRplus_opp_l, CRplus_0_r. reflexivity. + rewrite <- (CRplus_opp_r x). apply CRplus_le_compat. + exact H. apply CRle_refl. +Qed. + +Lemma CRmin_lt : forall {R : ConstructiveReals} (x y z : CRcarrier R), + z < x -> z < y -> z < CRmin x y. +Proof. + intros. unfold CRmin. + apply (CRmult_lt_reg_r (CR_of_Q R 2)). + rewrite <- CR_of_Q_zero. apply CR_of_Q_lt; reflexivity. + rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r. + apply (CRplus_lt_reg_l _ (CRabs _ (y - x) - (z*CR_of_Q R 2))). + unfold CRminus. rewrite CRplus_assoc. rewrite CRplus_opp_l, CRplus_0_r. + rewrite (CRplus_comm (CRabs R (y + - x))). + rewrite (CRplus_comm (x+y)), CRplus_assoc. + rewrite <- (CRplus_assoc (CRabs R (y + - x))), CRplus_opp_r, CRplus_0_l. + rewrite <- (CRplus_comm (x+y)). + apply CRabs_def1. + - unfold CRminus. rewrite <- (CRplus_comm y), CRplus_assoc. + apply CRplus_lt_compat_l. + apply (CRplus_lt_reg_l R (-x)). + rewrite CRopp_mult_distr_l. + rewrite <- CRplus_assoc, CRplus_opp_l, CRplus_0_l. + rewrite (CR_of_Q_plus R 1 1), CR_of_Q_one, CRmult_plus_distr_l. + rewrite CRmult_1_r. apply CRplus_le_lt_compat. + apply CRlt_asym. + apply CRopp_gt_lt_contravar, H. + apply CRopp_gt_lt_contravar, H. + - rewrite CRopp_plus_distr, CRopp_involutive. + rewrite CRplus_comm, CRplus_assoc. + apply CRplus_lt_compat_l. + apply (CRplus_lt_reg_l R (-y)). + rewrite CRopp_mult_distr_l. + rewrite <- CRplus_assoc, CRplus_opp_l, CRplus_0_l. + rewrite (CR_of_Q_plus R 1 1), CR_of_Q_one, CRmult_plus_distr_l. + rewrite CRmult_1_r. apply CRplus_le_lt_compat. + apply CRlt_asym. + apply CRopp_gt_lt_contravar, H0. + apply CRopp_gt_lt_contravar, H0. +Qed. + +Lemma CRmin_contract : forall {R : ConstructiveReals} (x y a : CRcarrier R), + CRabs _ (CRmin x a - CRmin y a) <= CRabs _ (x - y). +Proof. + intros. unfold CRmin. + unfold CRminus. rewrite CRopp_mult_distr_l, <- CRmult_plus_distr_r. + rewrite (CRabs_morph + _ ((x - y + (CRabs _ (a - y) - CRabs _ (a - x))) * CR_of_Q R (1 # 2))). + rewrite CRabs_mult, (CRabs_right (CR_of_Q R (1 # 2))). + 2: rewrite <- CR_of_Q_zero; apply CR_of_Q_le; discriminate. + apply (CRle_trans _ + ((CRabs _ (x - y) * 1 + CRabs _ (x-y) * 1) + * CR_of_Q R (1 # 2))). + apply CRmult_le_compat_r. + rewrite <- CR_of_Q_zero. apply CR_of_Q_le. discriminate. + apply (CRle_trans + _ (CRabs _ (x - y) + CRabs _ (CRabs _ (a - y) - CRabs _ (a - x)))). + apply CRabs_triang. rewrite CRmult_1_r. apply CRplus_le_compat_l. + rewrite (CRabs_morph (x-y) ((a-y)-(a-x))). + apply CRabs_triang_inv2. + unfold CRminus. rewrite (CRplus_comm (a + - y)). + rewrite <- CRplus_assoc. apply CRplus_morph. 2: reflexivity. + rewrite CRplus_comm, CRopp_plus_distr, <- CRplus_assoc. + rewrite CRplus_opp_r, CRopp_involutive, CRplus_0_l. + reflexivity. + rewrite <- CRmult_plus_distr_l, <- CR_of_Q_one. + rewrite <- (CR_of_Q_plus R 1 1). + rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((1 + 1) * (1 # 2))%Q with 1%Q. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r. apply CRle_refl. + unfold CRminus. apply CRmult_morph. 2: reflexivity. + do 4 rewrite CRplus_assoc. apply CRplus_morph. reflexivity. + rewrite <- CRplus_assoc. rewrite CRplus_comm, CRopp_plus_distr. + rewrite CRplus_assoc. apply CRplus_morph. reflexivity. + rewrite CRopp_plus_distr. rewrite (CRplus_comm (-a)). + rewrite CRplus_assoc, <- (CRplus_assoc (-a)), CRplus_opp_l. + rewrite CRplus_0_l, CRopp_involutive. reflexivity. +Qed. + +Lemma CRmin_glb : forall {R : ConstructiveReals} (x y z:CRcarrier R), + z <= x -> z <= y -> z <= CRmin x y. +Proof. + intros. unfold CRmin. + apply (CRmult_le_reg_r (CR_of_Q R 2)). + rewrite <- CR_of_Q_zero. apply CR_of_Q_lt; reflexivity. + rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r. + apply (CRplus_le_reg_l (CRabs _ (y-x) - (z*CR_of_Q R 2))). + unfold CRminus. rewrite CRplus_assoc, CRplus_opp_l, CRplus_0_r. + rewrite (CRplus_comm (CRabs R (y + - x) + - (z * CR_of_Q R 2))). + rewrite CRplus_assoc, <- (CRplus_assoc (- CRabs R (y + - x))). + rewrite CRplus_opp_l, CRplus_0_l. + apply CRabs_le. split. + - do 2 rewrite CRopp_plus_distr. + rewrite CRopp_involutive, (CRplus_comm y), CRplus_assoc. + apply CRplus_le_compat_l, (CRplus_le_reg_l y). + rewrite <- CRplus_assoc, CRplus_opp_r, CRplus_0_l. + rewrite (CR_of_Q_plus R 1 1), CR_of_Q_one, CRmult_plus_distr_l. + rewrite CRmult_1_r. apply CRplus_le_compat; exact H0. + - rewrite (CRplus_comm x), CRplus_assoc. apply CRplus_le_compat_l. + apply (CRplus_le_reg_l (-x)). + rewrite <- CRplus_assoc, CRplus_opp_l, CRplus_0_l. + rewrite CRopp_mult_distr_l. + rewrite (CR_of_Q_plus R 1 1), CR_of_Q_one, CRmult_plus_distr_l. + rewrite CRmult_1_r. + apply CRplus_le_compat; apply CRopp_ge_le_contravar; exact H. +Qed. + +Lemma CRmin_assoc : forall {R : ConstructiveReals} (a b c : CRcarrier R), + CRmin a (CRmin b c) == CRmin (CRmin a b) c. +Proof. + split. + - apply CRmin_glb. + + apply (CRle_trans _ (CRmin a b)). + apply CRmin_l. apply CRmin_l. + + apply CRmin_glb. + apply (CRle_trans _ (CRmin a b)). + apply CRmin_l. apply CRmin_r. apply CRmin_r. + - apply CRmin_glb. + + apply CRmin_glb. apply CRmin_l. + apply (CRle_trans _ (CRmin b c)). + apply CRmin_r. apply CRmin_l. + + apply (CRle_trans _ (CRmin b c)). + apply CRmin_r. apply CRmin_r. +Qed. + +Lemma CRlt_min : forall {R : ConstructiveReals} (x y z : CRcarrier R), + z < CRmin x y -> prod (z < x) (z < y). +Proof. + intros. destruct (CR_Q_dense R _ _ H) as [q qmaj]. + destruct qmaj. + split. + - apply (CRlt_le_trans _ (CR_of_Q R q) _ c). + intro abs. apply (CRlt_asym _ _ c0). + apply (CRle_lt_trans _ x). apply CRmin_l. exact abs. + - apply (CRlt_le_trans _ (CR_of_Q R q) _ c). + intro abs. apply (CRlt_asym _ _ c0). + apply (CRle_lt_trans _ y). apply CRmin_r. exact abs. +Qed. + + + +(* Maximum *) + +Definition CRmax {R : ConstructiveReals} (x y : CRcarrier R) : CRcarrier R + := (x + y + CRabs _ (y - x)) * CR_of_Q _ (1#2). + +Add Parametric Morphism {R : ConstructiveReals} : CRmax + with signature (CReq R) ==> (CReq R) ==> (CReq R) + as CRmax_morph. +Proof. + intros. unfold CRmax. + apply CRmult_morph. 2: reflexivity. unfold CRminus. + rewrite H, H0. reflexivity. +Qed. + +Instance CRmax_morphT + : forall {R : ConstructiveReals}, + CMorphisms.Proper + (CMorphisms.respectful (CReq R) (CMorphisms.respectful (CReq R) (CReq R))) (@CRmax R). +Proof. + intros R x y H z t H0. + rewrite H, H0. reflexivity. +Qed. + +Lemma CRmax_lub : forall {R : ConstructiveReals} (x y z:CRcarrier R), + x <= z -> y <= z -> CRmax x y <= z. +Proof. + intros. unfold CRmax. + apply (CRmult_le_reg_r (CR_of_Q _ 2)). rewrite <- CR_of_Q_zero. + apply CR_of_Q_lt; reflexivity. + rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r. + apply (CRplus_le_reg_l (-x-y)). + rewrite <- CRplus_assoc. unfold CRminus. + rewrite <- CRopp_plus_distr, CRplus_opp_l, CRplus_0_l. + apply CRabs_le. split. + - repeat rewrite CRopp_plus_distr. + do 2 rewrite CRopp_involutive. + rewrite (CRplus_comm x), CRplus_assoc. apply CRplus_le_compat_l. + apply (CRplus_le_reg_l (-x)). + rewrite <- CRplus_assoc, CRplus_opp_l, CRplus_0_l. + rewrite (CR_of_Q_plus _ 1 1), CRmult_plus_distr_l, CR_of_Q_one, CRmult_1_r. + rewrite CRopp_plus_distr. + apply CRplus_le_compat; apply CRopp_ge_le_contravar; assumption. + - rewrite (CRplus_comm y), CRopp_plus_distr, CRplus_assoc. + apply CRplus_le_compat_l. + apply (CRplus_le_reg_l y). + rewrite <- CRplus_assoc, CRplus_opp_r, CRplus_0_l. + rewrite (CR_of_Q_plus _ 1 1), CRmult_plus_distr_l, CR_of_Q_one, CRmult_1_r. + apply CRplus_le_compat; assumption. +Qed. + +Lemma CRmax_l : forall {R : ConstructiveReals} (x y : CRcarrier R), + x <= CRmax x y. +Proof. + intros. unfold CRmax. + apply (CRmult_le_reg_r (CR_of_Q R 2)). rewrite <- CR_of_Q_zero. + apply CR_of_Q_lt; reflexivity. + rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r. + setoid_replace 2%Q with (1+1)%Q. rewrite CR_of_Q_plus, CR_of_Q_one. + rewrite CRmult_plus_distr_l, CRmult_1_r, CRplus_assoc. + apply CRplus_le_compat_l. + apply (CRplus_le_reg_l (-y)). + rewrite <- CRplus_assoc, CRplus_opp_l, CRplus_0_l. + rewrite CRabs_minus_sym, CRplus_comm. + apply CRle_abs. reflexivity. +Qed. + +Lemma CRmax_r : forall {R : ConstructiveReals} (x y : CRcarrier R), + y <= CRmax x y. +Proof. + intros. unfold CRmax. + apply (CRmult_le_reg_r (CR_of_Q _ 2)). rewrite <- CR_of_Q_zero. + apply CR_of_Q_lt; reflexivity. + rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r. + rewrite (CR_of_Q_plus _ 1 1), CRmult_plus_distr_l, CR_of_Q_one, CRmult_1_r. + rewrite (CRplus_comm x). + rewrite CRplus_assoc. apply CRplus_le_compat_l. + apply (CRplus_le_reg_l (-x)). + rewrite <- CRplus_assoc, CRplus_opp_l, CRplus_0_l. + rewrite CRplus_comm. apply CRle_abs. +Qed. + +Lemma CRposPartAbsMax : forall {R : ConstructiveReals} (x : CRcarrier R), + CRmax 0 x == (x + CRabs _ x) * (CR_of_Q R (1#2)). +Proof. + intros. unfold CRmax. unfold CRminus. rewrite CRplus_0_l. + apply CRmult_morph. 2: reflexivity. rewrite CRopp_0, CRplus_0_r. reflexivity. +Qed. + +Lemma CRmax_sym : forall {R : ConstructiveReals} (x y : CRcarrier R), + CRmax x y == CRmax y x. +Proof. + intros. unfold CRmax. + rewrite CRabs_minus_sym. apply CRmult_morph. + 2: reflexivity. rewrite (CRplus_comm x y). reflexivity. +Qed. + +Lemma CRmax_plus : forall {R : ConstructiveReals} (x y z : CRcarrier R), + x + CRmax y z == CRmax (x + y) (x + z). +Proof. + intros. unfold CRmax. + setoid_replace (x + z - (x + y)) with (z-y). + apply (CRmult_eq_reg_r (CR_of_Q _ 2)). + left. rewrite <- CR_of_Q_zero. apply CR_of_Q_lt; reflexivity. + rewrite CRmult_plus_distr_r. + rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r. + rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite (CR_of_Q_plus _ 1 1), CRmult_plus_distr_l, CR_of_Q_one, CRmult_1_r. + rewrite CRmult_1_r. + do 3 rewrite (CRplus_assoc x). apply CRplus_morph. reflexivity. + do 2 rewrite <- CRplus_assoc. apply CRplus_morph. 2: reflexivity. + rewrite (CRplus_comm x). apply CRplus_assoc. + unfold CRminus. rewrite CRopp_plus_distr. rewrite <- CRplus_assoc. + apply CRplus_morph. 2: reflexivity. + rewrite CRplus_comm, <- CRplus_assoc, CRplus_opp_l. + apply CRplus_0_l. +Qed. + +Lemma CRmax_left : forall {R : ConstructiveReals} (x y : CRcarrier R), + y <= x -> CRmax x y == x. +Proof. + intros. unfold CRmax. + apply (CRmult_eq_reg_r (CR_of_Q R 2)). + left. rewrite <- CR_of_Q_zero. apply CR_of_Q_lt; reflexivity. + rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r. + rewrite (CR_of_Q_plus _ 1 1), CRmult_plus_distr_l, CR_of_Q_one, CRmult_1_r. + rewrite CRplus_assoc. apply CRplus_morph. reflexivity. + rewrite CRabs_left. unfold CRminus. rewrite CRopp_plus_distr, CRopp_involutive. + rewrite <- CRplus_assoc, CRplus_opp_r, CRplus_0_l. reflexivity. + rewrite <- (CRplus_opp_r x). apply CRplus_le_compat_r. exact H. +Qed. + +Lemma CRmax_right : forall {R : ConstructiveReals} (x y : CRcarrier R), + x <= y -> CRmax x y == y. +Proof. + intros. unfold CRmax. + apply (CRmult_eq_reg_r (CR_of_Q R 2)). + left. rewrite <- CR_of_Q_zero. apply CR_of_Q_lt; reflexivity. + rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r. + rewrite (CR_of_Q_plus _ 1 1), CRmult_plus_distr_l, CR_of_Q_one, CRmult_1_r. + rewrite (CRplus_comm x y). + rewrite CRplus_assoc. apply CRplus_morph. reflexivity. + rewrite CRabs_right. unfold CRminus. rewrite CRplus_comm. + rewrite CRplus_assoc, CRplus_opp_l, CRplus_0_r. reflexivity. + rewrite <- (CRplus_opp_r x). apply CRplus_le_compat_r. exact H. +Qed. + +Lemma CRmax_contract : forall {R : ConstructiveReals} (x y a : CRcarrier R), + CRabs _ (CRmax x a - CRmax y a) <= CRabs _ (x - y). +Proof. + intros. unfold CRmax. + rewrite (CRabs_morph + _ ((x - y + (CRabs _ (a - x) - CRabs _ (a - y))) * CR_of_Q R (1 # 2))). + rewrite CRabs_mult, (CRabs_right (CR_of_Q R (1 # 2))). + 2: rewrite <- CR_of_Q_zero; apply CR_of_Q_le; discriminate. + apply (CRle_trans + _ ((CRabs _ (x - y) * 1 + CRabs _ (x-y) * 1) + * CR_of_Q R (1 # 2))). + apply CRmult_le_compat_r. + rewrite <- CR_of_Q_zero. apply CR_of_Q_le. discriminate. + apply (CRle_trans + _ (CRabs _ (x - y) + CRabs _ (CRabs _ (a - x) - CRabs _ (a - y)))). + apply CRabs_triang. rewrite CRmult_1_r. apply CRplus_le_compat_l. + rewrite (CRabs_minus_sym x y). + rewrite (CRabs_morph (y-x) ((a-x)-(a-y))). + apply CRabs_triang_inv2. + unfold CRminus. rewrite (CRplus_comm (a + - x)). + rewrite <- CRplus_assoc. apply CRplus_morph. 2: reflexivity. + rewrite CRplus_comm, CRopp_plus_distr, <- CRplus_assoc. + rewrite CRplus_opp_r, CRopp_involutive, CRplus_0_l. + reflexivity. + rewrite <- CRmult_plus_distr_l, <- CR_of_Q_one. + rewrite <- (CR_of_Q_plus R 1 1). + rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((1 + 1) * (1 # 2))%Q with 1%Q. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r. apply CRle_refl. + unfold CRminus. rewrite CRopp_mult_distr_l. + rewrite <- CRmult_plus_distr_r. apply CRmult_morph. 2: reflexivity. + do 4 rewrite CRplus_assoc. apply CRplus_morph. reflexivity. + rewrite <- CRplus_assoc. rewrite CRplus_comm, CRopp_plus_distr. + rewrite CRplus_assoc. apply CRplus_morph. reflexivity. + rewrite CRopp_plus_distr. rewrite (CRplus_comm (-a)). + rewrite CRplus_assoc, <- (CRplus_assoc (-a)), CRplus_opp_l. + rewrite CRplus_0_l. apply CRplus_comm. +Qed. + +Lemma CRmax_lub_lt : forall {R : ConstructiveReals} (x y z : CRcarrier R), + x < z -> y < z -> CRmax x y < z. +Proof. + intros. unfold CRmax. + apply (CRmult_lt_reg_r (CR_of_Q R 2)). + rewrite <- CR_of_Q_zero. apply CR_of_Q_lt; reflexivity. + rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r. + apply (CRplus_lt_reg_l _ (-y -x)). unfold CRminus. + rewrite CRplus_assoc, <- (CRplus_assoc (-x)), <- (CRplus_assoc (-x)). + rewrite CRplus_opp_l, CRplus_0_l, <- CRplus_assoc, CRplus_opp_l, CRplus_0_l. + apply CRabs_def1. + - rewrite (CRplus_comm y), (CRplus_comm (-y)), CRplus_assoc. + apply CRplus_lt_compat_l. + apply (CRplus_lt_reg_l _ y). + rewrite <- CRplus_assoc, CRplus_opp_r, CRplus_0_l. + rewrite (CR_of_Q_plus R 1 1), CR_of_Q_one, CRmult_plus_distr_l. + rewrite CRmult_1_r. apply CRplus_le_lt_compat. + apply CRlt_asym, H0. exact H0. + - rewrite CRopp_plus_distr, CRopp_involutive. + rewrite CRplus_assoc. apply CRplus_lt_compat_l. + apply (CRplus_lt_reg_l _ x). + rewrite <- CRplus_assoc, CRplus_opp_r, CRplus_0_l. + rewrite (CR_of_Q_plus R 1 1), CR_of_Q_one, CRmult_plus_distr_l. + rewrite CRmult_1_r. apply CRplus_le_lt_compat. + apply CRlt_asym, H. exact H. +Qed. + +Lemma CRmax_assoc : forall {R : ConstructiveReals} (a b c : CRcarrier R), + CRmax a (CRmax b c) == CRmax (CRmax a b) c. +Proof. + split. + - apply CRmax_lub. + + apply CRmax_lub. apply CRmax_l. + apply (CRle_trans _ (CRmax b c)). + apply CRmax_l. apply CRmax_r. + + apply (CRle_trans _ (CRmax b c)). + apply CRmax_r. apply CRmax_r. + - apply CRmax_lub. + + apply (CRle_trans _ (CRmax a b)). + apply CRmax_l. apply CRmax_l. + + apply CRmax_lub. + apply (CRle_trans _ (CRmax a b)). + apply CRmax_r. apply CRmax_l. apply CRmax_r. +Qed. + +Lemma CRmax_min_mult_neg : + forall {R : ConstructiveReals} (p q r:CRcarrier R), + r <= 0 -> CRmax (r * p) (r * q) == r * CRmin p q. +Proof. + intros R p q r H. unfold CRmin, CRmax. + setoid_replace (r * q - r * p) with (r * (q - p)). + rewrite CRabs_mult. + rewrite (CRabs_left r), <- CRmult_assoc. + apply CRmult_morph. 2: reflexivity. unfold CRminus. + rewrite <- CRopp_mult_distr_l, CRopp_mult_distr_r, + CRmult_plus_distr_l, CRmult_plus_distr_l. + reflexivity. exact H. + unfold CRminus. rewrite CRmult_plus_distr_l, CRopp_mult_distr_r. reflexivity. +Qed. + +Lemma CRlt_max : forall {R : ConstructiveReals} (x y z : CRcarrier R), + CRmax x y < z -> prod (x < z) (y < z). +Proof. + intros. destruct (CR_Q_dense R _ _ H) as [q qmaj]. + destruct qmaj. + split. + - apply (CRlt_le_trans _ (CR_of_Q R q)). + apply (CRle_lt_trans _ (CRmax x y)). apply CRmax_l. exact c. + apply CRlt_asym, c0. + - apply (CRlt_le_trans _ (CR_of_Q R q)). + apply (CRle_lt_trans _ (CRmax x y)). apply CRmax_r. exact c. + apply CRlt_asym, c0. +Qed. + +Lemma CRmax_mult : + forall {R : ConstructiveReals} (p q r:CRcarrier R), + 0 <= r -> CRmax (r * p) (r * q) == r * CRmax p q. +Proof. + intros R p q r H. unfold CRmin, CRmax. + setoid_replace (r * q - r * p) with (r * (q - p)). + rewrite CRabs_mult. + rewrite (CRabs_right r), <- CRmult_assoc. + apply CRmult_morph. 2: reflexivity. + rewrite CRmult_plus_distr_l, CRmult_plus_distr_l. + reflexivity. exact H. + unfold CRminus. rewrite CRmult_plus_distr_l, CRopp_mult_distr_r. reflexivity. +Qed. + +Lemma CRmin_max_mult_neg : + forall {R : ConstructiveReals} (p q r:CRcarrier R), + r <= 0 -> CRmin (r * p) (r * q) == r * CRmax p q. +Proof. + intros R p q r H. unfold CRmin, CRmax. + setoid_replace (r * q - r * p) with (r * (q - p)). + rewrite CRabs_mult. + rewrite (CRabs_left r), <- CRmult_assoc. + apply CRmult_morph. 2: reflexivity. unfold CRminus. + rewrite CRopp_mult_distr_l, CRopp_involutive, + CRmult_plus_distr_l, CRmult_plus_distr_l. + reflexivity. exact H. + unfold CRminus. rewrite CRmult_plus_distr_l, CRopp_mult_distr_r. reflexivity. +Qed. diff --git a/theories/Reals/Abstract/ConstructiveLUB.v b/theories/Reals/Abstract/ConstructiveLUB.v new file mode 100644 index 0000000000..4ae24de154 --- /dev/null +++ b/theories/Reals/Abstract/ConstructiveLUB.v @@ -0,0 +1,413 @@ +(************************************************************************) +(* * The Coq Proof Assistant / The Coq Development Team *) +(* v * INRIA, CNRS and contributors - Copyright 1999-2019 *) +(* <O___,, * (see CREDITS file for the list of authors) *) +(* \VV/ **************************************************************) +(* // * This file is distributed under the terms of the *) +(* * GNU Lesser General Public License Version 2.1 *) +(* * (see LICENSE file for the text of the license) *) +(************************************************************************) +(************************************************************************) + +(** Proof that LPO and the excluded middle for negations imply + the existence of least upper bounds for all non-empty and bounded + subsets of the real numbers. *) + +Require Import QArith_base Qabs. +Require Import ConstructiveReals. +Require Import ConstructiveAbs. +Require Import ConstructiveLimits. +Require Import Logic.ConstructiveEpsilon. + +Local Open Scope ConstructiveReals. + +Definition sig_forall_dec_T : Type + := forall (P : nat -> Prop), (forall n, {P n} + {~P n}) + -> {n | ~P n} + {forall n, P n}. + +Definition sig_not_dec_T : Type := forall P : Prop, { ~~P } + { ~P }. + +Definition is_upper_bound {R : ConstructiveReals} + (E:CRcarrier R -> Prop) (m:CRcarrier R) + := forall x:CRcarrier R, E x -> x <= m. + +Definition is_lub {R : ConstructiveReals} + (E:CRcarrier R -> Prop) (m:CRcarrier R) := + is_upper_bound E m /\ (forall b:CRcarrier R, is_upper_bound E b -> m <= b). + +Lemma CRlt_lpo_dec : forall {R : ConstructiveReals} (x y : CRcarrier R), + (forall (P : nat -> Prop), (forall n, {P n} + {~P n}) + -> {n | ~P n} + {forall n, P n}) + -> sum (x < y) (y <= x). +Proof. + intros R x y lpo. + assert (forall (z:CRcarrier R) (n : nat), z < z + CR_of_Q R (1 # Pos.of_nat (S n))). + { intros. apply (CRle_lt_trans _ (z+0)). + rewrite CRplus_0_r. apply CRle_refl. apply CRplus_lt_compat_l. + apply CR_of_Q_pos. reflexivity. } + pose (fun n:nat => let (q,_) := CR_Q_dense + R x (x + CR_of_Q R (1 # Pos.of_nat (S n))) (H x n) + in q) + as xn. + pose (fun n:nat => let (q,_) := CR_Q_dense + R y (y + CR_of_Q R (1 # Pos.of_nat (S n))) (H y n) + in q) + as yn. + destruct (lpo (fun n => Qle (yn n) (xn n + (1 # Pos.of_nat (S n))))). + - intro n. destruct (Q_dec (yn n) (xn n + (1 # Pos.of_nat (S n)))). + destruct s. left. apply Qlt_le_weak, q. + right. apply (Qlt_not_le _ _ q). left. + rewrite q. apply Qle_refl. + - left. destruct s as [n nmaj]. apply Qnot_le_lt in nmaj. + apply (CRlt_le_trans _ (CR_of_Q R (xn n))). + unfold xn. + destruct (CR_Q_dense R x (x + CR_of_Q R (1 # Pos.of_nat (S n))) (H x n)). + exact (fst p). apply (CRle_trans _ (CR_of_Q R (yn n - (1 # Pos.of_nat (S n))))). + apply CR_of_Q_le. rewrite <- (Qplus_le_l _ _ (1# Pos.of_nat (S n))). + ring_simplify. apply Qlt_le_weak, nmaj. + unfold yn. + destruct (CR_Q_dense R y (y + CR_of_Q R (1 # Pos.of_nat (S n))) (H y n)). + unfold Qminus. rewrite CR_of_Q_plus, CR_of_Q_opp. + apply (CRplus_le_reg_r (CR_of_Q R (1 # Pos.of_nat (S n)))). + rewrite CRplus_assoc, CRplus_opp_l, CRplus_0_r. + apply CRlt_asym, (snd p). + - right. apply (CR_cv_le (fun n => CR_of_Q R (yn n)) + (fun n => CR_of_Q R (xn n) + CR_of_Q R (1 # Pos.of_nat (S n)))). + + intro n. rewrite <- CR_of_Q_plus. apply CR_of_Q_le. exact (q n). + + intro p. exists (Pos.to_nat p). intros. + unfold yn. + destruct (CR_Q_dense R y (y + CR_of_Q R (1 # Pos.of_nat (S i))) (H y i)). + rewrite CRabs_right. apply (CRplus_le_reg_r y). + unfold CRminus. rewrite CRplus_assoc, CRplus_opp_l, CRplus_0_r. + rewrite CRplus_comm. + apply (CRle_trans _ (y + CR_of_Q R (1 # Pos.of_nat (S i)))). + apply CRlt_asym, (snd p0). apply CRplus_le_compat_l. + apply CR_of_Q_le. unfold Qle, Qnum, Qden. + rewrite Z.mul_1_l, Z.mul_1_l. apply Pos2Z.pos_le_pos. + apply Pos2Nat.inj_le. rewrite Nat2Pos.id. + apply le_S, H0. discriminate. rewrite <- (CRplus_opp_r y). + apply CRplus_le_compat_r, CRlt_asym, p0. + + apply (CR_cv_proper _ (x+0)). 2: rewrite CRplus_0_r; reflexivity. + apply CR_cv_plus. + intro p. exists (Pos.to_nat p). intros. + unfold xn. + destruct (CR_Q_dense R x (x + CR_of_Q R (1 # Pos.of_nat (S i))) (H x i)). + rewrite CRabs_right. apply (CRplus_le_reg_r x). + unfold CRminus. rewrite CRplus_assoc, CRplus_opp_l, CRplus_0_r. + rewrite CRplus_comm. + apply (CRle_trans _ (x + CR_of_Q R (1 # Pos.of_nat (S i)))). + apply CRlt_asym, (snd p0). apply CRplus_le_compat_l. + apply CR_of_Q_le. unfold Qle, Qnum, Qden. + rewrite Z.mul_1_l, Z.mul_1_l. apply Pos2Z.pos_le_pos. + apply Pos2Nat.inj_le. rewrite Nat2Pos.id. + apply le_S, H0. discriminate. rewrite <- (CRplus_opp_r x). + apply CRplus_le_compat_r, CRlt_asym, p0. + intro p. exists (Pos.to_nat p). intros. + unfold CRminus. rewrite CRopp_0, CRplus_0_r, CRabs_right. + apply CR_of_Q_le. unfold Qle, Qnum, Qden. + rewrite Z.mul_1_l, Z.mul_1_l. apply Pos2Z.pos_le_pos. + apply Pos2Nat.inj_le. rewrite Nat2Pos.id. + apply le_S, H0. discriminate. + rewrite <- CR_of_Q_zero. apply CR_of_Q_le. discriminate. +Qed. + +Lemma is_upper_bound_dec : + forall {R : ConstructiveReals} (E:CRcarrier R -> Prop) (x:CRcarrier R), + sig_forall_dec_T + -> sig_not_dec_T + -> { is_upper_bound E x } + { ~is_upper_bound E x }. +Proof. + intros R E x lpo sig_not_dec. + destruct (sig_not_dec (~exists y:CRcarrier R, E y /\ CRltProp R x y)). + - left. intros y H. + destruct (CRlt_lpo_dec x y lpo). 2: exact c. + exfalso. apply n. intro abs. apply abs. clear abs. + exists y. split. exact H. apply CRltForget. exact c. + - right. intro abs. apply n. intros [y [H H0]]. + specialize (abs y H). apply CRltEpsilon in H0. contradiction. +Qed. + +Lemma is_upper_bound_epsilon : + forall {R : ConstructiveReals} (E:CRcarrier R -> Prop), + sig_forall_dec_T + -> sig_not_dec_T + -> (exists x:CRcarrier R, is_upper_bound E x) + -> { n:nat | is_upper_bound E (CR_of_Q R (Z.of_nat n # 1)) }. +Proof. + intros R E lpo sig_not_dec Ebound. + apply constructive_indefinite_ground_description_nat. + - intro n. apply is_upper_bound_dec. exact lpo. exact sig_not_dec. + - destruct Ebound as [x H]. destruct (CRup_nat x) as [n nmaj]. exists n. + intros y ey. specialize (H y ey). + apply (CRle_trans _ x _ H). apply CRlt_asym, nmaj. +Qed. + +Lemma is_upper_bound_not_epsilon : + forall {R : ConstructiveReals} (E:CRcarrier R -> Prop), + sig_forall_dec_T + -> sig_not_dec_T + -> (exists x : CRcarrier R, E x) + -> { m:nat | ~is_upper_bound E (-CR_of_Q R (Z.of_nat m # 1)) }. +Proof. + intros R E lpo sig_not_dec H. + apply constructive_indefinite_ground_description_nat. + - intro n. + destruct (is_upper_bound_dec E (-CR_of_Q R (Z.of_nat n # 1)) lpo sig_not_dec). + right. intro abs. contradiction. left. exact n0. + - destruct H as [x H]. destruct (CRup_nat (-x)) as [n H0]. + exists n. intro abs. specialize (abs x H). + apply abs. rewrite <- (CRopp_involutive x). + apply CRopp_gt_lt_contravar. exact H0. +Qed. + +(* Decidable Dedekind cuts are Cauchy reals. *) +Record DedekindDecCut : Type := + { + DDupcut : Q -> Prop; + DDproper : forall q r : Q, (q == r -> DDupcut q -> DDupcut r)%Q; + DDlow : Q; + DDhigh : Q; + DDdec : forall q:Q, { DDupcut q } + { ~DDupcut q }; + DDinterval : forall q r : Q, Qle q r -> DDupcut q -> DDupcut r; + DDhighProp : DDupcut DDhigh; + DDlowProp : ~DDupcut DDlow; + }. + +Lemma DDlow_below_up : forall (upcut : DedekindDecCut) (a b : Q), + DDupcut upcut a -> ~DDupcut upcut b -> Qlt b a. +Proof. + intros. destruct (Qlt_le_dec b a). exact q. + exfalso. apply H0. apply (DDinterval upcut a). + exact q. exact H. +Qed. + +Fixpoint DDcut_limit_fix (upcut : DedekindDecCut) (r : Q) (n : nat) : + Qlt 0 r + -> (DDupcut upcut (DDlow upcut + (Z.of_nat n#1) * r)) + -> { q : Q | DDupcut upcut q /\ ~DDupcut upcut (q - r) }. +Proof. + destruct n. + - intros. exfalso. simpl in H0. + apply (DDproper upcut _ (DDlow upcut)) in H0. 2: ring. + exact (DDlowProp upcut H0). + - intros. destruct (DDdec upcut (DDlow upcut + (Z.of_nat n # 1) * r)). + + exact (DDcut_limit_fix upcut r n H d). + + exists (DDlow upcut + (Z.of_nat (S n) # 1) * r)%Q. split. + exact H0. intro abs. + apply (DDproper upcut _ (DDlow upcut + (Z.of_nat n # 1) * r)) in abs. + contradiction. + rewrite Nat2Z.inj_succ. unfold Z.succ. rewrite <- Qinv_plus_distr. + ring. +Qed. + +Lemma DDcut_limit : forall (upcut : DedekindDecCut) (r : Q), + Qlt 0 r + -> { q : Q | DDupcut upcut q /\ ~DDupcut upcut (q - r) }. +Proof. + intros. + destruct (Qarchimedean ((DDhigh upcut - DDlow upcut)/r)) as [n nmaj]. + apply (DDcut_limit_fix upcut r (Pos.to_nat n) H). + apply (Qmult_lt_r _ _ r) in nmaj. 2: exact H. + unfold Qdiv in nmaj. + rewrite <- Qmult_assoc, (Qmult_comm (/r)), Qmult_inv_r, Qmult_1_r in nmaj. + apply (DDinterval upcut (DDhigh upcut)). 2: exact (DDhighProp upcut). + apply Qlt_le_weak. apply (Qplus_lt_r _ _ (-DDlow upcut)). + rewrite Qplus_assoc, <- (Qplus_comm (DDlow upcut)), Qplus_opp_r, + Qplus_0_l, Qplus_comm. + rewrite positive_nat_Z. exact nmaj. + intros abs. rewrite abs in H. exact (Qlt_irrefl 0 H). +Qed. + +Lemma glb_dec_Q : forall {R : ConstructiveReals} (upcut : DedekindDecCut), + { x : CRcarrier R + | forall r:Q, (x < CR_of_Q R r -> DDupcut upcut r) + /\ (CR_of_Q R r < x -> ~DDupcut upcut r) }. +Proof. + intros. + assert (forall a b : Q, Qle a b -> Qle (-b) (-a)). + { intros. apply (Qplus_le_l _ _ (a+b)). ring_simplify. exact H. } + assert (CR_cauchy R (fun n:nat => CR_of_Q R (proj1_sig (DDcut_limit + upcut (1#Pos.of_nat n) (eq_refl _))))). + { intros p. exists (Pos.to_nat p). intros i j pi pj. + destruct (DDcut_limit upcut (1 # Pos.of_nat i) eq_refl), + (DDcut_limit upcut (1 # Pos.of_nat j) eq_refl); unfold proj1_sig. + apply (CRabs_le). split. + - intros. unfold CRminus. + rewrite <- CR_of_Q_opp, <- CR_of_Q_opp, <- CR_of_Q_plus. + apply CR_of_Q_le. + apply (Qplus_le_l _ _ x0). ring_simplify. + setoid_replace (-1 * (1 # p) + x0)%Q with (x0 - (1 # p))%Q. + 2: ring. apply (Qle_trans _ (x0- (1#Pos.of_nat j))). + apply Qplus_le_r. apply H. + apply Z2Nat.inj_le. discriminate. discriminate. simpl. + rewrite Nat2Pos.id. exact pj. intro abs. + subst j. inversion pj. pose proof (Pos2Nat.is_pos p). + rewrite H1 in H0. inversion H0. + apply Qlt_le_weak, (DDlow_below_up upcut). apply a. apply a0. + - unfold CRminus. rewrite <- CR_of_Q_opp, <- CR_of_Q_plus. + apply CR_of_Q_le. + apply (Qplus_le_l _ _ (x0-(1#p))). ring_simplify. + setoid_replace (x -1 * (1 # p))%Q with (x - (1 # p))%Q. + 2: ring. apply (Qle_trans _ (x- (1#Pos.of_nat i))). + apply Qplus_le_r. apply H. + apply Z2Nat.inj_le. discriminate. discriminate. simpl. + rewrite Nat2Pos.id. exact pi. intro abs. + subst i. inversion pi. pose proof (Pos2Nat.is_pos p). + rewrite H1 in H0. inversion H0. + apply Qlt_le_weak, (DDlow_below_up upcut). apply a0. apply a. } + apply CR_complete in H0. destruct H0 as [l lcv]. + exists l. split. + - intros. (* find an upper point between the limit and r *) + destruct (CR_cv_open_above _ (CR_of_Q R r) l lcv H0) as [p pmaj]. + specialize (pmaj p (le_refl p)). + unfold proj1_sig in pmaj. + destruct (DDcut_limit upcut (1 # Pos.of_nat p) eq_refl) as [q qmaj]. + apply (DDinterval upcut q). 2: apply qmaj. + destruct (Q_dec q r). destruct s. apply Qlt_le_weak, q0. + exfalso. apply (CR_of_Q_lt R) in q0. exact (CRlt_asym _ _ pmaj q0). + rewrite q0. apply Qle_refl. + - intros H0 abs. + assert ((CR_of_Q R r+l) * CR_of_Q R (1#2) < l). + { apply (CRmult_lt_reg_r (CR_of_Q R 2)). + apply CR_of_Q_pos. reflexivity. + rewrite CRmult_assoc, <- CR_of_Q_mult, (CR_of_Q_plus R 1 1). + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CR_of_Q_one, CRmult_plus_distr_l, CRmult_1_r, CRmult_1_r. + apply CRplus_lt_compat_r. exact H0. } + destruct (CR_cv_open_below _ _ l lcv H1) as [p pmaj]. + assert (0 < (l-CR_of_Q R r) * CR_of_Q R (1#2)). + { apply CRmult_lt_0_compat. rewrite <- (CRplus_opp_r (CR_of_Q R r)). + apply CRplus_lt_compat_r. exact H0. apply CR_of_Q_pos. reflexivity. } + destruct (CRup_nat (CRinv R _ (inr H2))) as [i imaj]. + destruct i. exfalso. simpl in imaj. + rewrite CR_of_Q_zero in imaj. + exact (CRlt_asym _ _ imaj (CRinv_0_lt_compat R _ (inr H2) H2)). + specialize (pmaj (max (S i) (S p)) (le_trans p (S p) _ (le_S p p (le_refl p)) (Nat.le_max_r (S i) (S p)))). + unfold proj1_sig in pmaj. + destruct (DDcut_limit upcut (1 # Pos.of_nat (max (S i) (S p))) eq_refl) + as [q qmaj]. + destruct qmaj. apply H4. clear H4. + apply (DDinterval upcut r). 2: exact abs. + apply (Qplus_le_l _ _ (1 # Pos.of_nat (Init.Nat.max (S i) (S p)))). + ring_simplify. apply (Qle_trans _ (r + (1 # Pos.of_nat (S i)))). + rewrite Qplus_le_r. unfold Qle,Qnum,Qden. + rewrite Z.mul_1_l, Z.mul_1_l. apply Pos2Z.pos_le_pos. + apply Pos2Nat.inj_le. rewrite Nat2Pos.id, Nat2Pos.id. + apply Nat.le_max_l. discriminate. discriminate. + apply (CRmult_lt_compat_l ((l - CR_of_Q R r) * CR_of_Q R (1 # 2))) in imaj. + rewrite CRinv_r in imaj. 2: exact H2. + destruct (Q_dec (r+(1#Pos.of_nat (S i))) q). destruct s. + apply Qlt_le_weak, q0. 2: rewrite q0; apply Qle_refl. + exfalso. apply (CR_of_Q_lt R) in q0. + apply (CRlt_asym _ _ pmaj). apply (CRlt_le_trans _ _ _ q0). + apply (CRplus_le_reg_l (-CR_of_Q R r)). + rewrite CR_of_Q_plus, <- CRplus_assoc, CRplus_opp_l, CRplus_0_l. + apply (CRmult_lt_compat_r (CR_of_Q R (1 # Pos.of_nat (S i)))) in imaj. + rewrite CRmult_1_l in imaj. + apply (CRle_trans _ ( + (l - CR_of_Q R r) * CR_of_Q R (1 # 2) * CR_of_Q R (Z.of_nat (S i) # 1) * + CR_of_Q R (1 # Pos.of_nat (S i)))). + apply CRlt_asym, imaj. rewrite CRmult_assoc, <- CR_of_Q_mult. + setoid_replace ((Z.of_nat (S i) # 1) * (1 # Pos.of_nat (S i)))%Q with 1%Q. + rewrite CR_of_Q_one, CRmult_1_r. + unfold CRminus. rewrite CRmult_plus_distr_r, (CRplus_comm (-CR_of_Q R r)). + rewrite (CRplus_comm (CR_of_Q R r)), CRmult_plus_distr_r. + rewrite CRplus_assoc. apply CRplus_le_compat_l. + rewrite <- CR_of_Q_mult, <- CR_of_Q_opp, <- CR_of_Q_mult, <- CR_of_Q_plus. + apply CR_of_Q_le. ring_simplify. apply Qle_refl. + unfold Qeq, Qmult, Qnum, Qden. rewrite Z.mul_1_r, Z.mul_1_r. + rewrite Z.mul_1_l, Pos.mul_1_l. unfold Z.of_nat. + apply f_equal. apply Pos.of_nat_succ. apply CR_of_Q_pos. reflexivity. +Qed. + +Lemma is_upper_bound_glb : + forall {R : ConstructiveReals} (E:CRcarrier R -> Prop), + sig_not_dec_T + -> sig_forall_dec_T + -> (exists x : CRcarrier R, E x) + -> (exists x : CRcarrier R, is_upper_bound E x) + -> { x : CRcarrier R + | forall r:Q, (x < CR_of_Q R r -> is_upper_bound E (CR_of_Q R r)) + /\ (CR_of_Q R r < x -> ~is_upper_bound E (CR_of_Q R r)) }. +Proof. + intros R E sig_not_dec lpo Einhab Ebound. + destruct (is_upper_bound_epsilon E lpo sig_not_dec Ebound) as [a luba]. + destruct (is_upper_bound_not_epsilon E lpo sig_not_dec Einhab) as [b glbb]. + pose (fun q => is_upper_bound E (CR_of_Q R q)) as upcut. + assert (forall q:Q, { upcut q } + { ~upcut q } ). + { intro q. apply is_upper_bound_dec. exact lpo. exact sig_not_dec. } + assert (forall q r : Q, (q <= r)%Q -> upcut q -> upcut r). + { intros. intros x Ex. specialize (H1 x Ex). intro abs. + apply H1. apply (CRle_lt_trans _ (CR_of_Q R r)). 2: exact abs. + apply CR_of_Q_le. exact H0. } + assert (upcut (Z.of_nat a # 1)%Q). + { intros x Ex. exact (luba x Ex). } + assert (~upcut (- Z.of_nat b # 1)%Q). + { intros abs. apply glbb. intros x Ex. + specialize (abs x Ex). rewrite <- CR_of_Q_opp. + exact abs. } + assert (forall q r : Q, (q == r)%Q -> upcut q -> upcut r). + { intros. intros x Ex. specialize (H4 x Ex). rewrite <- H3. exact H4. } + destruct (@glb_dec_Q R (Build_DedekindDecCut + upcut H3 (-Z.of_nat b # 1)%Q (Z.of_nat a # 1) + H H0 H1 H2)). + simpl in a0. exists x. intro r. split. + - intros. apply a0. exact H4. + - intros H6 abs. specialize (a0 r) as [_ a0]. apply a0. + exact H6. exact abs. +Qed. + +Lemma is_upper_bound_closed : + forall {R : ConstructiveReals} + (E:CRcarrier R -> Prop) (sig_forall_dec : sig_forall_dec_T) + (sig_not_dec : sig_not_dec_T) + (Einhab : exists x : CRcarrier R, E x) + (Ebound : exists x : CRcarrier R, is_upper_bound E x), + is_lub + E (proj1_sig (is_upper_bound_glb + E sig_not_dec sig_forall_dec Einhab Ebound)). +Proof. + intros. split. + - intros x Ex. + destruct (is_upper_bound_glb E sig_not_dec sig_forall_dec Einhab Ebound); simpl. + intro abs. destruct (CR_Q_dense R x0 x abs) as [q [qmaj H]]. + specialize (a q) as [a _]. specialize (a qmaj x Ex). + contradiction. + - intros. + destruct (is_upper_bound_glb E sig_not_dec sig_forall_dec Einhab Ebound); simpl. + intro abs. destruct (CR_Q_dense R b x abs) as [q [qmaj H0]]. + specialize (a q) as [_ a]. apply a. exact H0. + intros y Ey. specialize (H y Ey). intro abs2. + apply H. exact (CRlt_trans _ (CR_of_Q R q) _ qmaj abs2). +Qed. + +Lemma sig_lub : + forall {R : ConstructiveReals} (E:CRcarrier R -> Prop), + sig_forall_dec_T + -> sig_not_dec_T + -> (exists x : CRcarrier R, E x) + -> (exists x : CRcarrier R, is_upper_bound E x) + -> { u : CRcarrier R | is_lub E u }. +Proof. + intros R E sig_forall_dec sig_not_dec Einhab Ebound. + pose proof (is_upper_bound_closed E sig_forall_dec sig_not_dec Einhab Ebound). + destruct (is_upper_bound_glb + E sig_not_dec sig_forall_dec Einhab Ebound); simpl in H. + exists x. exact H. +Qed. + +Definition CRis_upper_bound {R : ConstructiveReals} (E:CRcarrier R -> Prop) (m:CRcarrier R) + := forall x:CRcarrier R, E x -> CRlt R m x -> False. + +Lemma CR_sig_lub : + forall {R : ConstructiveReals} (E:CRcarrier R -> Prop), + (forall x y : CRcarrier R, CReq R x y -> (E x <-> E y)) + -> sig_forall_dec_T + -> sig_not_dec_T + -> (exists x : CRcarrier R, E x) + -> (exists x : CRcarrier R, CRis_upper_bound E x) + -> { u : CRcarrier R | CRis_upper_bound E u /\ + forall y:CRcarrier R, CRis_upper_bound E y -> CRlt R y u -> False }. +Proof. + intros. exact (sig_lub E X X0 H0 H1). +Qed. diff --git a/theories/Reals/Abstract/ConstructiveLimits.v b/theories/Reals/Abstract/ConstructiveLimits.v new file mode 100644 index 0000000000..4a40cc8cb3 --- /dev/null +++ b/theories/Reals/Abstract/ConstructiveLimits.v @@ -0,0 +1,933 @@ +(************************************************************************) +(* * The Coq Proof Assistant / The Coq Development Team *) +(* v * INRIA, CNRS and contributors - Copyright 1999-2019 *) +(* <O___,, * (see CREDITS file for the list of authors) *) +(* \VV/ **************************************************************) +(* // * This file is distributed under the terms of the *) +(* * GNU Lesser General Public License Version 2.1 *) +(* * (see LICENSE file for the text of the license) *) +(************************************************************************) + +Require Import QArith Qabs. +Require Import ConstructiveReals. +Require Import ConstructiveAbs. +Require Import ConstructiveSum. + +Local Open Scope ConstructiveReals. + + +(** Definitions and basic properties of limits of real sequences + and series. *) + + +Lemma CR_cv_extens + : forall {R : ConstructiveReals} (xn yn : nat -> CRcarrier R) (l : CRcarrier R), + (forall n:nat, xn n == yn n) + -> CR_cv R xn l + -> CR_cv R yn l. +Proof. + intros. intro p. specialize (H0 p) as [n nmaj]. exists n. + intros. specialize (nmaj i H0). + apply (CRle_trans _ (CRabs R (CRminus R (xn i) l))). + 2: exact nmaj. rewrite <- CRabs_def. split. + - apply (CRle_trans _ (CRminus R (xn i) l)). + apply CRplus_le_compat_r. specialize (H i) as [H _]. exact H. + pose proof (CRabs_def R (CRminus R (xn i) l) (CRabs R (CRminus R (xn i) l))) + as [_ H1]. + apply H1. apply CRle_refl. + - apply (CRle_trans _ (CRopp R (CRminus R (xn i) l))). + intro abs. apply CRopp_lt_cancel, CRplus_lt_reg_r in abs. + specialize (H i) as [_ H]. contradiction. + pose proof (CRabs_def R (CRminus R (xn i) l) (CRabs R (CRminus R (xn i) l))) + as [_ H1]. + apply H1. apply CRle_refl. +Qed. + +Lemma CR_cv_opp : forall {R : ConstructiveReals} (xn : nat -> CRcarrier R) (l : CRcarrier R), + CR_cv R xn l + -> CR_cv R (fun n => - xn n) (- l). +Proof. + intros. intro p. specialize (H p) as [n nmaj]. + exists n. intros. specialize (nmaj i H). + apply (CRle_trans _ (CRabs R (CRminus R (xn i) l))). + 2: exact nmaj. clear nmaj H. + unfold CRminus. rewrite <- CRopp_plus_distr, CRabs_opp. + apply CRle_refl. +Qed. + +Lemma CR_cv_plus : forall {R : ConstructiveReals} (xn yn : nat -> CRcarrier R) (a b : CRcarrier R), + CR_cv R xn a + -> CR_cv R yn b + -> CR_cv R (fun n => xn n + yn n) (a + b). +Proof. + intros. intro p. + specialize (H (2*p)%positive) as [i imaj]. + specialize (H0 (2*p)%positive) as [j jmaj]. + exists (max i j). intros. + apply (CRle_trans + _ (CRabs R (CRplus R (CRminus R (xn i0) a) (CRminus R (yn i0) b)))). + apply CRabs_morph. + - unfold CRminus. + do 2 rewrite <- (Radd_assoc (CRisRing R)). + apply CRplus_morph. reflexivity. rewrite CRopp_plus_distr. + destruct (CRisRing R). rewrite Radd_comm, <- Radd_assoc. + apply CRplus_morph. reflexivity. + rewrite Radd_comm. reflexivity. + - apply (CRle_trans _ _ _ (CRabs_triang _ _)). + apply (CRle_trans _ (CRplus R (CR_of_Q R (1 # 2*p)) (CR_of_Q R (1 # 2*p)))). + apply CRplus_le_compat. apply imaj, (le_trans _ _ _ (Nat.le_max_l _ _) H). + apply jmaj, (le_trans _ _ _ (Nat.le_max_r _ _) H). + apply (CRle_trans _ (CR_of_Q R ((1 # 2 * p) + (1 # 2 * p)))). + apply CR_of_Q_plus. apply CR_of_Q_le. + rewrite Qinv_plus_distr. setoid_replace (1 + 1 # 2 * p) with (1 # p). + apply Qle_refl. reflexivity. +Qed. + +Lemma CR_cv_unique : forall {R : ConstructiveReals} (xn : nat -> CRcarrier R) + (a b : CRcarrier R), + CR_cv R xn a + -> CR_cv R xn b + -> a == b. +Proof. + intros. assert (CR_cv R (fun _ => CRzero R) (CRminus R b a)). + { apply (CR_cv_extens (fun n => CRminus R (xn n) (xn n))). + intro n. unfold CRminus. apply CRplus_opp_r. + apply CR_cv_plus. exact H0. apply CR_cv_opp, H. } + assert (forall q r : Q, 0 < q -> / q < r -> 1 < q * r)%Q. + { intros. apply (Qmult_lt_l _ _ q) in H3. + rewrite Qmult_inv_r in H3. exact H3. intro abs. + rewrite abs in H2. exact (Qlt_irrefl 0 H2). exact H2. } + clear H H0 xn. remember (CRminus R b a) as z. + assert (z == 0). split. + - intro abs. destruct (CR_Q_dense R _ _ abs) as [q [H0 H]]. + destruct (Qarchimedean (/(-q))) as [p pmaj]. + specialize (H1 p) as [n nmaj]. + specialize (nmaj n (le_refl n)). apply nmaj. + apply (CRlt_trans _ (CR_of_Q R (-q))). apply CR_of_Q_lt. + apply H2 in pmaj. + apply (Qmult_lt_r _ _ (1#p)) in pmaj. 2: reflexivity. + rewrite Qmult_1_l, <- Qmult_assoc in pmaj. + setoid_replace ((Z.pos p # 1) * (1 # p))%Q with 1%Q in pmaj. + rewrite Qmult_1_r in pmaj. exact pmaj. unfold Qeq, Qnum, Qden; simpl. + do 2 rewrite Pos.mul_1_r. reflexivity. + apply (Qplus_lt_l _ _ q). ring_simplify. + apply (lt_CR_of_Q R q 0). apply (CRlt_le_trans _ (CRzero R) _ H). + apply CR_of_Q_zero. + apply (CRlt_le_trans _ (CRopp R z)). + apply (CRle_lt_trans _ (CRopp R (CR_of_Q R q))). apply CR_of_Q_opp. + apply CRopp_gt_lt_contravar, H0. + apply (CRle_trans _ (CRabs R (CRopp R z))). + pose proof (CRabs_def R (CRopp R z) (CRabs R (CRopp R z))) as [_ H1]. + apply H1, CRle_refl. + apply CRabs_morph. unfold CRminus. symmetry. apply CRplus_0_l. + - intro abs. destruct (CR_Q_dense R _ _ abs) as [q [H0 H]]. + destruct (Qarchimedean (/q)) as [p pmaj]. + specialize (H1 p) as [n nmaj]. + specialize (nmaj n (le_refl n)). apply nmaj. + apply (CRlt_trans _ (CR_of_Q R q)). apply CR_of_Q_lt. + apply H2 in pmaj. + apply (Qmult_lt_r _ _ (1#p)) in pmaj. 2: reflexivity. + rewrite Qmult_1_l, <- Qmult_assoc in pmaj. + setoid_replace ((Z.pos p # 1) * (1 # p))%Q with 1%Q in pmaj. + rewrite Qmult_1_r in pmaj. exact pmaj. unfold Qeq, Qnum, Qden; simpl. + do 2 rewrite Pos.mul_1_r. reflexivity. + apply (lt_CR_of_Q R 0 q). apply (CRle_lt_trans _ (CRzero R)). + 2: exact H0. apply CR_of_Q_zero. + apply (CRlt_le_trans _ _ _ H). + apply (CRle_trans _ (CRabs R (CRopp R z))). + apply (CRle_trans _ (CRabs R z)). + pose proof (CRabs_def R z (CRabs R z)) as [_ H1]. + apply H1. apply CRle_refl. apply CRabs_opp. + apply CRabs_morph. unfold CRminus. symmetry. apply CRplus_0_l. + - subst z. apply (CRplus_eq_reg_l (CRopp R a)). + apply (CReq_trans _ (CRzero R)). apply CRplus_opp_l. + destruct (CRisRing R). + apply (CReq_trans _ (CRplus R b (CRopp R a))). apply CReq_sym, H. + apply Radd_comm. +Qed. + +Lemma CR_cv_eq : forall {R : ConstructiveReals} + (v u : nat -> CRcarrier R) (s : CRcarrier R), + (forall n:nat, u n == v n) + -> CR_cv R u s + -> CR_cv R v s. +Proof. + intros R v u s seq H1 p. specialize (H1 p) as [N H0]. + exists N. intros. unfold CRminus. rewrite <- seq. apply H0, H. +Qed. + +Lemma CR_cauchy_eq : forall {R : ConstructiveReals} + (un vn : nat -> CRcarrier R), + (forall n:nat, un n == vn n) + -> CR_cauchy R un + -> CR_cauchy R vn. +Proof. + intros. intro p. specialize (H0 p) as [n H0]. + exists n. intros. specialize (H0 i j H1 H2). + unfold CRminus in H0. rewrite <- CRabs_def. + rewrite <- CRabs_def in H0. + do 2 rewrite H in H0. exact H0. +Qed. + +Lemma CR_cv_proper : forall {R : ConstructiveReals} + (un : nat -> CRcarrier R) (a b : CRcarrier R), + CR_cv R un a + -> a == b + -> CR_cv R un b. +Proof. + intros. intro p. specialize (H p) as [n H]. + exists n. intros. unfold CRminus. rewrite <- H0. apply H, H1. +Qed. + +Instance CR_cv_morph + : forall {R : ConstructiveReals} (un : nat -> CRcarrier R), CMorphisms.Proper + (CMorphisms.respectful (CReq R) CRelationClasses.iffT) (CR_cv R un). +Proof. + split. intros. apply (CR_cv_proper un x). exact H0. exact H. + intros. apply (CR_cv_proper un y). exact H0. symmetry. exact H. +Qed. + +Lemma Un_cv_nat_real : forall {R : ConstructiveReals} + (un : nat -> CRcarrier R) (l : CRcarrier R), + CR_cv R un l + -> forall eps : CRcarrier R, + 0 < eps + -> { p : nat & forall i:nat, le p i -> CRabs R (un i - l) < eps }. +Proof. + intros. destruct (CR_archimedean R (CRinv R eps (inr H0))) as [k kmaj]. + assert (0 < CR_of_Q R (Z.pos k # 1)). + { rewrite <- CR_of_Q_zero. apply CR_of_Q_lt. reflexivity. } + specialize (H k) as [p pmaj]. + exists p. intros. + apply (CRle_lt_trans _ (CR_of_Q R (1 # k))). + apply pmaj, H. + apply (CRmult_lt_reg_l (CR_of_Q R (Z.pos k # 1))). exact H1. + rewrite <- CR_of_Q_mult. + apply (CRle_lt_trans _ 1). + rewrite <- CR_of_Q_one. apply CR_of_Q_le. + unfold Qle; simpl. do 2 rewrite Pos.mul_1_r. apply Z.le_refl. + apply (CRmult_lt_reg_r (CRinv R eps (inr H0))). + apply CRinv_0_lt_compat, H0. rewrite CRmult_1_l, CRmult_assoc. + rewrite CRinv_r, CRmult_1_r. exact kmaj. +Qed. + +Lemma Un_cv_real_nat : forall {R : ConstructiveReals} + (un : nat -> CRcarrier R) (l : CRcarrier R), + (forall eps : CRcarrier R, + 0 < eps + -> { p : nat & forall i:nat, le p i -> CRabs R (un i - l) < eps }) + -> CR_cv R un l. +Proof. + intros. intros n. + specialize (H (CR_of_Q R (1#n))) as [p pmaj]. + rewrite <- CR_of_Q_zero. apply CR_of_Q_lt. reflexivity. + exists p. intros. apply CRlt_asym. apply pmaj. apply H. +Qed. + +Definition series_cv {R : ConstructiveReals} + (un : nat -> CRcarrier R) (s : CRcarrier R) : Set + := CR_cv R (CRsum un) s. + +Definition series_cv_lim_lt {R : ConstructiveReals} + (un : nat -> CRcarrier R) (x : CRcarrier R) : Set + := { l : CRcarrier R & prod (series_cv un l) (l < x) }. + +Definition series_cv_le_lim {R : ConstructiveReals} + (x : CRcarrier R) (un : nat -> CRcarrier R) : Set + := { l : CRcarrier R & prod (series_cv un l) (x <= l) }. + +Lemma CR_cv_minus : + forall {R : ConstructiveReals} + (An Bn:nat -> CRcarrier R) (l1 l2:CRcarrier R), + CR_cv R An l1 -> CR_cv R Bn l2 + -> CR_cv R (fun i:nat => An i - Bn i) (l1 - l2). +Proof. + intros. apply CR_cv_plus. apply H. + intros p. specialize (H0 p) as [n H0]. exists n. + intros. setoid_replace (- Bn i - - l2) with (- (Bn i - l2)). + rewrite CRabs_opp. apply H0, H1. unfold CRminus. + rewrite CRopp_plus_distr, CRopp_involutive. reflexivity. +Qed. + +Lemma CR_cv_nonneg : + forall {R : ConstructiveReals} (An:nat -> CRcarrier R) (l:CRcarrier R), + CR_cv R An l + -> (forall n:nat, 0 <= An n) + -> 0 <= l. +Proof. + intros. intro abs. + destruct (Un_cv_nat_real _ l H (-l)) as [N H1]. + rewrite <- CRopp_0. apply CRopp_gt_lt_contravar. apply abs. + specialize (H1 N (le_refl N)). + pose proof (CRabs_def R (An N - l) (CRabs R (An N - l))) as [_ H2]. + apply (CRle_lt_trans _ _ _ (CRle_abs _)) in H1. + apply (H0 N). apply (CRplus_lt_reg_r (-l)). + rewrite CRplus_0_l. exact H1. +Qed. + +Lemma series_cv_unique : + forall {R : ConstructiveReals} (Un:nat -> CRcarrier R) (l1 l2:CRcarrier R), + series_cv Un l1 -> series_cv Un l2 -> l1 == l2. +Proof. + intros. apply (CR_cv_unique (CRsum Un)); assumption. +Qed. + +Lemma CR_cv_scale : forall {R : ConstructiveReals} (u : nat -> CRcarrier R) + (a : CRcarrier R) (s : CRcarrier R), + CR_cv R u s -> CR_cv R (fun n => u n * a) (s * a). +Proof. + intros. intros n. + destruct (CR_archimedean R (1 + CRabs R a)). + destruct (H (n * x)%positive). + exists x0. intros. + unfold CRminus. rewrite CRopp_mult_distr_l. + rewrite <- CRmult_plus_distr_r. + apply (CRle_trans _ ((CR_of_Q R (1 # n * x)) * CRabs R a)). + rewrite CRabs_mult. apply CRmult_le_compat_r. apply CRabs_pos. + apply c0, H0. + setoid_replace (1 # n * x)%Q with ((1 # n) *(1# x))%Q. 2: reflexivity. + rewrite <- (CRmult_1_r (CR_of_Q R (1#n))). + rewrite CR_of_Q_mult, CRmult_assoc. + apply CRmult_le_compat_l. rewrite <- CR_of_Q_zero. + apply CR_of_Q_le. discriminate. intro abs. + apply (CRmult_lt_compat_l (CR_of_Q R (Z.pos x #1))) in abs. + rewrite CRmult_1_r, <- CRmult_assoc, <- CR_of_Q_mult in abs. + rewrite (CR_of_Q_morph R ((Z.pos x # 1) * (1 # x))%Q 1%Q) in abs. + rewrite CR_of_Q_one, CRmult_1_l in abs. + apply (CRlt_asym _ _ abs), (CRlt_trans _ (1 + CRabs R a)). + 2: exact c. rewrite <- CRplus_0_l, <- CRplus_assoc. + apply CRplus_lt_compat_r. rewrite CRplus_0_r. apply CRzero_lt_one. + unfold Qmult, Qeq, Qnum, Qden. ring_simplify. rewrite Pos.mul_1_l. + reflexivity. + apply (CRlt_trans _ (1+CRabs R a)). 2: exact c. + rewrite CRplus_comm. + rewrite <- (CRplus_0_r 0). apply CRplus_le_lt_compat. + apply CRabs_pos. apply CRzero_lt_one. +Qed. + +Lemma CR_cv_const : forall {R : ConstructiveReals} (a : CRcarrier R), + CR_cv R (fun n => a) a. +Proof. + intros a p. exists O. intros. + unfold CRminus. rewrite CRplus_opp_r. + rewrite CRabs_right. rewrite <- CR_of_Q_zero. + apply CR_of_Q_le. discriminate. apply CRle_refl. +Qed. + +Lemma Rcv_cauchy_mod : forall {R : ConstructiveReals} + (un : nat -> CRcarrier R) (l : CRcarrier R), + CR_cv R un l -> CR_cauchy R un. +Proof. + intros. intros p. specialize (H (2*p)%positive) as [k H]. + exists k. intros n q H0 H1. + setoid_replace (1#p)%Q with ((1#2*p) + (1#2*p))%Q. + rewrite CR_of_Q_plus. + setoid_replace (un n - un q) with ((un n - l) - (un q - l)). + apply (CRle_trans _ _ _ (CRabs_triang _ _)). + apply CRplus_le_compat. + - apply H, H0. + - rewrite CRabs_opp. apply H. apply H1. + - unfold CRminus. rewrite CRplus_assoc. apply CRplus_morph. + reflexivity. rewrite CRplus_comm, CRopp_plus_distr, CRopp_involutive. + rewrite CRplus_assoc, CRplus_opp_r, CRplus_0_r. reflexivity. + - rewrite Qinv_plus_distr. reflexivity. +Qed. + +Lemma series_cv_eq : forall {R : ConstructiveReals} + (u v : nat -> CRcarrier R) (s : CRcarrier R), + (forall n:nat, u n == v n) + -> series_cv u s + -> series_cv v s. +Proof. + intros. intros p. specialize (H0 p). destruct H0 as [N H0]. + exists N. intros. unfold CRminus. + rewrite <- (CRsum_eq u). apply H0, H1. intros. apply H. +Qed. + +Lemma CR_growing_transit : forall {R : ConstructiveReals} (un : nat -> CRcarrier R), + (forall n:nat, un n <= un (S n)) + -> forall n p : nat, le n p -> un n <= un p. +Proof. + induction p. + - intros. inversion H0. apply CRle_refl. + - intros. apply Nat.le_succ_r in H0. destruct H0. + apply (CRle_trans _ (un p)). apply IHp, H0. apply H. + subst n. apply CRle_refl. +Qed. + +Lemma growing_ineq : + forall {R : ConstructiveReals} (Un:nat -> CRcarrier R) (l:CRcarrier R), + (forall n:nat, Un n <= Un (S n)) + -> CR_cv R Un l -> forall n:nat, Un n <= l. +Proof. + intros. intro abs. + destruct (Un_cv_nat_real _ l H0 (Un n - l)) as [N H1]. + rewrite <- (CRplus_opp_r l). apply CRplus_lt_compat_r. exact abs. + specialize (H1 (max n N) (Nat.le_max_r _ _)). + apply (CRle_lt_trans _ _ _ (CRle_abs _)) in H1. + apply CRplus_lt_reg_r in H1. + apply (CR_growing_transit Un H n (max n N)). apply Nat.le_max_l. + exact H1. +Qed. + +Lemma CR_cv_open_below + : forall {R : ConstructiveReals} + (un : nat -> CRcarrier R) (m l : CRcarrier R), + CR_cv R un l + -> m < l + -> { n : nat & forall i:nat, le n i -> m < un i }. +Proof. + intros. apply CRlt_minus in H0. + pose proof (Un_cv_nat_real _ l H (l-m) H0) as [n nmaj]. + exists n. intros. specialize (nmaj i H1). + apply CRabs_lt in nmaj. + destruct nmaj as [_ nmaj]. unfold CRminus in nmaj. + rewrite CRopp_plus_distr, CRopp_involutive, CRplus_comm in nmaj. + apply CRplus_lt_reg_l in nmaj. + apply (CRplus_lt_reg_l R (-m)). rewrite CRplus_opp_l. + apply (CRplus_lt_reg_r (-un i)). rewrite CRplus_0_l. + rewrite CRplus_assoc, CRplus_opp_r, CRplus_0_r. exact nmaj. +Qed. + +Lemma CR_cv_open_above + : forall {R : ConstructiveReals} + (un : nat -> CRcarrier R) (m l : CRcarrier R), + CR_cv R un l + -> l < m + -> { n : nat & forall i:nat, le n i -> un i < m }. +Proof. + intros. apply CRlt_minus in H0. + pose proof (Un_cv_nat_real _ l H (m-l) H0) as [n nmaj]. + exists n. intros. specialize (nmaj i H1). + apply CRabs_lt in nmaj. + destruct nmaj as [nmaj _]. apply CRplus_lt_reg_r in nmaj. + exact nmaj. +Qed. + +Lemma CR_cv_bound_down : forall {R : ConstructiveReals} + (u : nat -> CRcarrier R) (A l : CRcarrier R) (N : nat), + (forall n:nat, le N n -> A <= u n) + -> CR_cv R u l + -> A <= l. +Proof. + intros. intro r. + apply (CRplus_lt_compat_r (-l)) in r. rewrite CRplus_opp_r in r. + destruct (Un_cv_nat_real _ l H0 (A - l) r) as [n H1]. + apply (H (n+N)%nat). + rewrite <- (plus_0_l N). rewrite Nat.add_assoc. + apply Nat.add_le_mono_r. apply le_0_n. + specialize (H1 (n+N)%nat). apply (CRplus_lt_reg_r (-l)). + assert (n + N >= n)%nat. rewrite <- (plus_0_r n). rewrite <- plus_assoc. + apply Nat.add_le_mono_l. apply le_0_n. specialize (H1 H2). + apply (CRle_lt_trans _ (CRabs R (u (n + N)%nat - l))). + apply CRle_abs. assumption. +Qed. + +Lemma CR_cv_bound_up : forall {R : ConstructiveReals} + (u : nat -> CRcarrier R) (A l : CRcarrier R) (N : nat), + (forall n:nat, le N n -> u n <= A) + -> CR_cv R u l + -> l <= A. +Proof. + intros. intro r. + apply (CRplus_lt_compat_r (-A)) in r. rewrite CRplus_opp_r in r. + destruct (Un_cv_nat_real _ l H0 (l-A) r) as [n H1]. + apply (H (n+N)%nat). + - rewrite <- (plus_0_l N). apply Nat.add_le_mono_r. apply le_0_n. + - specialize (H1 (n+N)%nat). apply (CRplus_lt_reg_l R (l - A - u (n+N)%nat)). + unfold CRminus. repeat rewrite CRplus_assoc. + rewrite CRplus_opp_l, CRplus_0_r, (CRplus_comm (-A)). + rewrite CRplus_assoc, CRplus_opp_r, CRplus_0_r. + apply (CRle_lt_trans _ _ _ (CRle_abs _)). + fold (l - u (n+N)%nat). rewrite CRabs_minus_sym. apply H1. + rewrite <- (plus_0_r n). rewrite <- plus_assoc. + apply Nat.add_le_mono_l. apply le_0_n. +Qed. + +Lemma series_cv_maj : forall {R : ConstructiveReals} + (un vn : nat -> CRcarrier R) (s : CRcarrier R), + (forall n:nat, CRabs R (un n) <= vn n) + -> series_cv vn s + -> { l : CRcarrier R & prod (series_cv un l) (l <= s) }. +Proof. + intros. destruct (CR_complete R (CRsum un)). + - intros n. + specialize (H0 (2*n)%positive) as [N maj]. + exists N. intros i j H0 H1. + apply (CRle_trans _ (CRsum vn (max i j) - CRsum vn (min i j))). + apply Abs_sum_maj. apply H. + setoid_replace (CRsum vn (max i j) - CRsum vn (min i j)) + with (CRabs R (CRsum vn (max i j) - (CRsum vn (min i j)))). + setoid_replace (CRsum vn (Init.Nat.max i j) - CRsum vn (Init.Nat.min i j)) + with (CRsum vn (Init.Nat.max i j) - s - (CRsum vn (Init.Nat.min i j) - s)). + apply (CRle_trans _ _ _ (CRabs_triang _ _)). + setoid_replace (1#n)%Q with ((1#2*n) + (1#2*n))%Q. + rewrite CR_of_Q_plus. + apply CRplus_le_compat. + apply maj. apply (le_trans _ i). assumption. apply Nat.le_max_l. + rewrite CRabs_opp. apply maj. + apply Nat.min_case. apply (le_trans _ i). assumption. apply le_refl. + assumption. rewrite Qinv_plus_distr. reflexivity. + unfold CRminus. rewrite CRplus_assoc. apply CRplus_morph. + reflexivity. rewrite CRopp_plus_distr, CRopp_involutive. + rewrite CRplus_comm, CRplus_assoc, CRplus_opp_r, CRplus_0_r. + reflexivity. + rewrite CRabs_right. reflexivity. + rewrite <- (CRplus_opp_r (CRsum vn (Init.Nat.min i j))). + apply CRplus_le_compat. apply pos_sum_more. + intros. apply (CRle_trans _ (CRabs R (un k))). apply CRabs_pos. + apply H. apply (le_trans _ i). apply Nat.le_min_l. apply Nat.le_max_l. + apply CRle_refl. + - exists x. split. assumption. + (* x <= s *) + apply (CRplus_le_reg_r (-x)). rewrite CRplus_opp_r. + apply (CR_cv_bound_down (fun n => CRsum vn n - CRsum un n) _ _ 0). + intros. rewrite <- (CRplus_opp_r (CRsum un n)). + apply CRplus_le_compat. apply sum_Rle. + intros. apply (CRle_trans _ (CRabs R (un k))). + apply CRle_abs. apply H. apply CRle_refl. + apply CR_cv_plus. assumption. + apply CR_cv_opp. assumption. +Qed. + +Lemma series_cv_abs_lt + : forall {R : ConstructiveReals} (un vn : nat -> CRcarrier R) (l : CRcarrier R), + (forall n:nat, CRabs R (un n) <= vn n) + -> series_cv_lim_lt vn l + -> series_cv_lim_lt un l. +Proof. + intros. destruct H0 as [x [H0 H1]]. + destruct (series_cv_maj un vn x H H0) as [x0 H2]. + exists x0. split. apply H2. apply (CRle_lt_trans _ x). + apply H2. apply H1. +Qed. + +Definition series_cv_abs {R : ConstructiveReals} (u : nat -> CRcarrier R) + : CR_cauchy R (CRsum (fun n => CRabs R (u n))) + -> { l : CRcarrier R & series_cv u l }. +Proof. + intros. apply CR_complete in H. destruct H. + destruct (series_cv_maj u (fun k => CRabs R (u k)) x). + intro n. apply CRle_refl. assumption. exists x0. apply p. +Qed. + +Lemma series_cv_abs_eq + : forall {R : ConstructiveReals} (u : nat -> CRcarrier R) (a : CRcarrier R) + (cau : CR_cauchy R (CRsum (fun n => CRabs R (u n)))), + series_cv u a + -> (a == (let (l,_):= series_cv_abs u cau in l))%ConstructiveReals. +Proof. + intros. destruct (series_cv_abs u cau). + apply (series_cv_unique u). exact H. exact s. +Qed. + +Lemma series_cv_abs_cv + : forall {R : ConstructiveReals} (u : nat -> CRcarrier R) + (cau : CR_cauchy R (CRsum (fun n => CRabs R (u n)))), + series_cv u (let (l,_):= series_cv_abs u cau in l). +Proof. + intros. destruct (series_cv_abs u cau). exact s. +Qed. + +Lemma series_cv_opp : forall {R : ConstructiveReals} + (s : CRcarrier R) (u : nat -> CRcarrier R), + series_cv u s + -> series_cv (fun n => - u n) (- s). +Proof. + intros. intros p. specialize (H p) as [N H]. + exists N. intros n H0. + setoid_replace (CRsum (fun n0 : nat => - u n0) n - - s) + with (-(CRsum (fun n0 : nat => u n0) n - s)). + rewrite CRabs_opp. + apply H, H0. unfold CRminus. + rewrite sum_opp. rewrite CRopp_plus_distr. reflexivity. +Qed. + +Lemma series_cv_scale : forall {R : ConstructiveReals} + (a : CRcarrier R) (s : CRcarrier R) (u : nat -> CRcarrier R), + series_cv u s + -> series_cv (fun n => (u n) * a) (s * a). +Proof. + intros. + apply (CR_cv_eq _ (fun n => CRsum u n * a)). + intro n. rewrite sum_scale. reflexivity. apply CR_cv_scale, H. +Qed. + +Lemma series_cv_plus : forall {R : ConstructiveReals} + (u v : nat -> CRcarrier R) (s t : CRcarrier R), + series_cv u s + -> series_cv v t + -> series_cv (fun n => u n + v n) (s + t). +Proof. + intros. apply (CR_cv_eq _ (fun n => CRsum u n + CRsum v n)). + intro n. symmetry. apply sum_plus. apply CR_cv_plus. exact H. exact H0. +Qed. + +Lemma series_cv_nonneg : forall {R : ConstructiveReals} + (u : nat -> CRcarrier R) (s : CRcarrier R), + (forall n:nat, 0 <= u n) -> series_cv u s -> 0 <= s. +Proof. + intros. apply (CRle_trans 0 (CRsum u 0)). apply H. + apply (growing_ineq (CRsum u)). intro n. simpl. + rewrite <- CRplus_0_r. apply CRplus_le_compat. + rewrite CRplus_0_r. apply CRle_refl. apply H. apply H0. +Qed. + +Lemma CR_cv_le : forall {R : ConstructiveReals} + (u v : nat -> CRcarrier R) (a b : CRcarrier R), + (forall n:nat, u n <= v n) + -> CR_cv R u a + -> CR_cv R v b + -> a <= b. +Proof. + intros. apply (CRplus_le_reg_r (-a)). rewrite CRplus_opp_r. + apply (CR_cv_bound_down (fun i:nat => v i - u i) _ _ 0). + intros. rewrite <- (CRplus_opp_l (u n)). + unfold CRminus. + rewrite (CRplus_comm (v n)). apply CRplus_le_compat_l. + apply H. apply CR_cv_plus. exact H1. apply CR_cv_opp, H0. +Qed. + +Lemma CR_cv_abs_cont : forall {R : ConstructiveReals} + (u : nat -> CRcarrier R) (s : CRcarrier R), + CR_cv R u s + -> CR_cv R (fun n => CRabs R (u n)) (CRabs R s). +Proof. + intros. intros eps. specialize (H eps) as [N lim]. + exists N. intros n H. + apply (CRle_trans _ (CRabs R (u n - s))). apply CRabs_triang_inv2. + apply lim. assumption. +Qed. + +Lemma CR_cv_dist_cont : forall {R : ConstructiveReals} + (u : nat -> CRcarrier R) (a s : CRcarrier R), + CR_cv R u s + -> CR_cv R (fun n => CRabs R (a - u n)) (CRabs R (a - s)). +Proof. + intros. apply CR_cv_abs_cont. + intros eps. specialize (H eps) as [N lim]. + exists N. intros n H. + setoid_replace (a - u n - (a - s)) with (s - (u n)). + specialize (lim n). + rewrite CRabs_minus_sym. + apply lim. assumption. + unfold CRminus. rewrite CRopp_plus_distr, CRopp_involutive. + rewrite (CRplus_comm a), (CRplus_comm s). + rewrite CRplus_assoc. apply CRplus_morph. reflexivity. + rewrite <- CRplus_assoc, CRplus_opp_r, CRplus_0_l. reflexivity. +Qed. + +Lemma series_cv_triangle : forall {R : ConstructiveReals} + (u : nat -> CRcarrier R) (s sAbs : CRcarrier R), + series_cv u s + -> series_cv (fun n => CRabs R (u n)) sAbs + -> CRabs R s <= sAbs. +Proof. + intros. + apply (CR_cv_le (fun n => CRabs R (CRsum u n)) + (CRsum (fun n => CRabs R (u n)))). + intros. apply multiTriangleIneg. apply CR_cv_abs_cont. assumption. assumption. +Qed. + +Lemma CR_double : forall {R : ConstructiveReals} (x:CRcarrier R), + CR_of_Q R 2 * x == x + x. +Proof. + intros R x. rewrite (CR_of_Q_morph R 2 (1+1)). + 2: reflexivity. rewrite CR_of_Q_plus, CR_of_Q_one. + rewrite CRmult_plus_distr_r, CRmult_1_l. reflexivity. +Qed. + +Lemma GeoCvZero : forall {R : ConstructiveReals}, + CR_cv R (fun n:nat => CRpow (CR_of_Q R (1#2)) n) 0. +Proof. + intro R. assert (forall n:nat, INR n < CRpow (CR_of_Q R 2) n). + { induction n. unfold INR; simpl. rewrite CR_of_Q_zero. + apply CRzero_lt_one. unfold INR. fold (1+n)%nat. + rewrite Nat2Z.inj_add. + rewrite (CR_of_Q_morph R _ ((Z.of_nat 1 # 1) + (Z.of_nat n #1))). + 2: symmetry; apply Qinv_plus_distr. + rewrite CR_of_Q_plus. + replace (CRpow (CR_of_Q R 2) (1 + n)) + with (CR_of_Q R 2 * CRpow (CR_of_Q R 2) n). + 2: reflexivity. rewrite CR_double. + apply CRplus_le_lt_compat. + 2: exact IHn. simpl. rewrite CR_of_Q_one. + apply pow_R1_Rle. rewrite <- CR_of_Q_one. apply CR_of_Q_le. discriminate. } + intros p. exists (Pos.to_nat p). intros. + unfold CRminus. rewrite CRopp_0. rewrite CRplus_0_r. + rewrite CRabs_right. + 2: apply pow_le; rewrite <- CR_of_Q_zero; apply CR_of_Q_le; discriminate. + apply CRlt_asym. + apply (CRmult_lt_reg_l (CR_of_Q R (Z.pos p # 1))). + rewrite <- CR_of_Q_zero. apply CR_of_Q_lt. reflexivity. rewrite <- CR_of_Q_mult. + rewrite (CR_of_Q_morph R ((Z.pos p # 1) * (1 # p)) 1). + 2: unfold Qmult, Qeq, Qnum, Qden; ring_simplify; reflexivity. + apply (CRmult_lt_reg_r (CRpow (CR_of_Q R 2) i)). + apply pow_lt. simpl. rewrite <- CR_of_Q_zero. + apply CR_of_Q_lt. reflexivity. + rewrite CRmult_assoc. rewrite pow_mult. + rewrite (pow_proper (CR_of_Q R (1 # 2) * CR_of_Q R 2) 1), pow_one. + rewrite CRmult_1_r, CR_of_Q_one, CRmult_1_l. + apply (CRle_lt_trans _ (INR i)). 2: exact (H i). clear H. + apply CR_of_Q_le. unfold Qle,Qnum,Qden. + do 2 rewrite Z.mul_1_r. + rewrite <- positive_nat_Z. apply Nat2Z.inj_le, H0. + rewrite <- CR_of_Q_mult. setoid_replace ((1#2)*2)%Q with 1%Q. + apply CR_of_Q_one. reflexivity. +Qed. + +Lemma GeoFiniteSum : forall {R : ConstructiveReals} (n:nat), + CRsum (CRpow (CR_of_Q R (1#2))) n == CR_of_Q R 2 - CRpow (CR_of_Q R (1#2)) n. +Proof. + induction n. + - unfold CRsum, CRpow. simpl (1%ConstructiveReals). + unfold CRminus. rewrite (CR_of_Q_morph R _ (1+1)). + rewrite CR_of_Q_plus, CR_of_Q_one, CRplus_assoc. + rewrite CRplus_opp_r, CRplus_0_r. reflexivity. reflexivity. + - setoid_replace (CRsum (CRpow (CR_of_Q R (1 # 2))) (S n)) + with (CRsum (CRpow (CR_of_Q R (1 # 2))) n + CRpow (CR_of_Q R (1 # 2)) (S n)). + 2: reflexivity. + rewrite IHn. clear IHn. unfold CRminus. + rewrite CRplus_assoc. apply CRplus_morph. reflexivity. + apply (CRplus_eq_reg_l + (CRpow (CR_of_Q R (1 # 2)) n + CRpow (CR_of_Q R (1 # 2)) (S n))). + rewrite (CRplus_assoc _ _ (-CRpow (CR_of_Q R (1 # 2)) (S n))), + CRplus_opp_r, CRplus_0_r. + rewrite (CRplus_comm (CRpow (CR_of_Q R (1 # 2)) n)), CRplus_assoc. + rewrite <- (CRplus_assoc (CRpow (CR_of_Q R (1 # 2)) n)), CRplus_opp_r, + CRplus_0_l, <- CR_double. + setoid_replace (CRpow (CR_of_Q R (1 # 2)) (S n)) + with (CR_of_Q R (1 # 2) * CRpow (CR_of_Q R (1 # 2)) n). + 2: reflexivity. + rewrite <- CRmult_assoc, <- CR_of_Q_mult. + setoid_replace (2 * (1 # 2))%Q with 1%Q. + rewrite CR_of_Q_one. apply CRmult_1_l. reflexivity. +Qed. + +Lemma GeoHalfBelowTwo : forall {R : ConstructiveReals} (n:nat), + CRsum (CRpow (CR_of_Q R (1#2))) n < CR_of_Q R 2. +Proof. + intros. rewrite <- (CRplus_0_r (CR_of_Q R 2)), GeoFiniteSum. + apply CRplus_lt_compat_l. rewrite <- CRopp_0. + apply CRopp_gt_lt_contravar. + apply pow_lt. rewrite <- CR_of_Q_zero. apply CR_of_Q_lt. reflexivity. +Qed. + +Lemma GeoHalfTwo : forall {R : ConstructiveReals}, + series_cv (fun n => CRpow (CR_of_Q R (1#2)) n) (CR_of_Q R 2). +Proof. + intro R. + apply (CR_cv_eq _ (fun n => CR_of_Q R 2 - CRpow (CR_of_Q R (1 # 2)) n)). + - intro n. rewrite GeoFiniteSum. reflexivity. + - assert (forall n:nat, INR n < CRpow (CR_of_Q R 2) n). + { induction n. unfold INR; simpl. rewrite CR_of_Q_zero. + apply CRzero_lt_one. apply (CRlt_le_trans _ (CRpow (CR_of_Q R 2) n + 1)). + unfold INR. + rewrite Nat2Z.inj_succ, <- Z.add_1_l. + rewrite (CR_of_Q_morph R _ (1 + (Z.of_nat n #1))). + 2: symmetry; apply Qinv_plus_distr. rewrite CR_of_Q_plus. + rewrite CRplus_comm. rewrite CR_of_Q_one. + apply CRplus_lt_compat_r, IHn. + setoid_replace (CRpow (CR_of_Q R 2) (S n)) + with (CRpow (CR_of_Q R 2) n + CRpow (CR_of_Q R 2) n). + apply CRplus_le_compat. apply CRle_refl. + apply pow_R1_Rle. rewrite <- CR_of_Q_one. apply CR_of_Q_le. discriminate. + rewrite <- CR_double. reflexivity. } + intros n. exists (Pos.to_nat n). intros. + setoid_replace (CR_of_Q R 2 - CRpow (CR_of_Q R (1 # 2)) i - CR_of_Q R 2) + with (- CRpow (CR_of_Q R (1 # 2)) i). + rewrite CRabs_opp. rewrite CRabs_right. + assert (0 < CR_of_Q R 2). + { rewrite <- CR_of_Q_zero. apply CR_of_Q_lt. reflexivity. } + rewrite (pow_proper _ (CRinv R (CR_of_Q R 2) (inr H1))). + rewrite pow_inv. apply CRlt_asym. + apply (CRmult_lt_reg_l (CRpow (CR_of_Q R 2) i)). apply pow_lt, H1. + rewrite CRinv_r. + apply (CRmult_lt_reg_r (CR_of_Q R (Z.pos n#1))). + rewrite <- CR_of_Q_zero. apply CR_of_Q_lt. reflexivity. + rewrite CRmult_1_l, CRmult_assoc. + rewrite <- CR_of_Q_mult. + rewrite (CR_of_Q_morph R ((1 # n) * (Z.pos n # 1)) 1). 2: reflexivity. + rewrite CR_of_Q_one, CRmult_1_r. apply (CRle_lt_trans _ (INR i)). + 2: apply H. apply CR_of_Q_le. + unfold Qle, Qnum, Qden. do 2 rewrite Z.mul_1_r. destruct i. + exfalso. inversion H0. pose proof (Pos2Nat.is_pos n). + rewrite H3 in H2. inversion H2. + apply Pos2Z.pos_le_pos. apply Pos2Nat.inj_le. + apply (le_trans _ _ _ H0). rewrite SuccNat2Pos.id_succ. apply le_refl. + apply (CRmult_eq_reg_l (CR_of_Q R 2)). right. exact H1. + rewrite CRinv_r. rewrite <- CR_of_Q_mult. + setoid_replace (2 * (1 # 2))%Q with 1%Q. + apply CR_of_Q_one. reflexivity. + apply CRlt_asym, pow_lt. rewrite <- CR_of_Q_zero. + apply CR_of_Q_lt. reflexivity. + unfold CRminus. rewrite CRplus_comm, <- CRplus_assoc. + rewrite CRplus_opp_l, CRplus_0_l. reflexivity. +Qed. + +Lemma series_cv_remainder_maj : forall {R : ConstructiveReals} (u : nat -> CRcarrier R) + (s eps : CRcarrier R) + (N : nat), + series_cv u s + -> 0 < eps + -> (forall n:nat, 0 <= u n) + -> CRabs R (CRsum u N - s) <= eps + -> forall n:nat, CRsum (fun k=> u (N + S k)%nat) n <= eps. +Proof. + intros. pose proof (sum_assoc u N n). + rewrite <- (CRsum_eq (fun k : nat => u (S N + k)%nat)). + apply (CRplus_le_reg_l (CRsum u N)). rewrite <- H3. + apply (CRle_trans _ s). apply growing_ineq. + 2: apply H. + intro k. simpl. rewrite <- CRplus_0_r, CRplus_assoc. + apply CRplus_le_compat_l. rewrite CRplus_0_l. apply H1. + rewrite CRabs_minus_sym in H2. + rewrite CRplus_comm. apply (CRplus_le_reg_r (-CRsum u N)). + rewrite CRplus_assoc. rewrite CRplus_opp_r. rewrite CRplus_0_r. + apply (CRle_trans _ (CRabs R (s - CRsum u N))). apply CRle_abs. + assumption. intros. rewrite Nat.add_succ_r. reflexivity. +Qed. + +Lemma series_cv_abs_remainder : forall {R : ConstructiveReals} (u : nat -> CRcarrier R) + (s sAbs : CRcarrier R) + (n : nat), + series_cv u s + -> series_cv (fun n => CRabs R (u n)) sAbs + -> CRabs R (CRsum u n - s) + <= sAbs - CRsum (fun n => CRabs R (u n)) n. +Proof. + intros. + apply (CR_cv_le (fun N => CRabs R (CRsum u n - (CRsum u (n + N)))) + (fun N => CRsum (fun n : nat => CRabs R (u n)) (n + N) + - CRsum (fun n : nat => CRabs R (u n)) n)). + - intro N. destruct N. rewrite plus_0_r. unfold CRminus. + rewrite CRplus_opp_r. rewrite CRplus_opp_r. + rewrite CRabs_right. apply CRle_refl. apply CRle_refl. + rewrite Nat.add_succ_r. + replace (S (n + N)) with (S n + N)%nat. 2: reflexivity. + unfold CRminus. rewrite sum_assoc. rewrite sum_assoc. + rewrite CRopp_plus_distr. + rewrite <- CRplus_assoc, CRplus_opp_r, CRplus_0_l, CRabs_opp. + rewrite CRplus_comm, <- CRplus_assoc, CRplus_opp_l. + rewrite CRplus_0_l. apply multiTriangleIneg. + - apply CR_cv_dist_cont. intros eps. + specialize (H eps) as [N lim]. + exists N. intros. rewrite plus_comm. apply lim. apply (le_trans N i). + assumption. rewrite <- (plus_0_r i). rewrite <- plus_assoc. + apply Nat.add_le_mono_l. apply le_0_n. + - apply CR_cv_plus. 2: apply CR_cv_const. intros eps. + specialize (H0 eps) as [N lim]. + exists N. intros. rewrite plus_comm. apply lim. apply (le_trans N i). + assumption. rewrite <- (plus_0_r i). rewrite <- plus_assoc. + apply Nat.add_le_mono_l. apply le_0_n. +Qed. + +Lemma series_cv_minus : forall {R : ConstructiveReals} + (u v : nat -> CRcarrier R) (s t : CRcarrier R), + series_cv u s + -> series_cv v t + -> series_cv (fun n => u n - v n) (s - t). +Proof. + intros. apply (CR_cv_eq _ (fun n => CRsum u n - CRsum v n)). + intro n. symmetry. unfold CRminus. rewrite sum_plus. + rewrite sum_opp. reflexivity. + apply CR_cv_plus. exact H. apply CR_cv_opp. exact H0. +Qed. + +Lemma series_cv_le : forall {R : ConstructiveReals} + (un vn : nat -> CRcarrier R) (a b : CRcarrier R), + (forall n:nat, un n <= vn n) + -> series_cv un a + -> series_cv vn b + -> a <= b. +Proof. + intros. apply (CRplus_le_reg_r (-a)). rewrite CRplus_opp_r. + apply (series_cv_nonneg (fun n => vn n - un n)). + intro n. apply (CRplus_le_reg_r (un n)). + rewrite CRplus_0_l. unfold CRminus. + rewrite CRplus_assoc, CRplus_opp_l, CRplus_0_r. + apply H. apply series_cv_minus; assumption. +Qed. + +Lemma series_cv_series : forall {R : ConstructiveReals} + (u : nat -> nat -> CRcarrier R) (s : nat -> CRcarrier R) (n : nat), + (forall i:nat, le i n -> series_cv (u i) (s i)) + -> series_cv (fun i => CRsum (fun j => u j i) n) (CRsum s n). +Proof. + induction n. + - intros. simpl. specialize (H O). + apply (series_cv_eq (u O)). reflexivity. apply H. apply le_refl. + - intros. simpl. apply (series_cv_plus). 2: apply (H (S n)). + apply IHn. 2: apply le_refl. intros. apply H. + apply (le_trans _ n _ H0). apply le_S. apply le_refl. +Qed. + +Lemma CR_cv_shift : + forall {R : ConstructiveReals} f k l, + CR_cv R (fun n => f (n + k)%nat) l -> CR_cv R f l. +Proof. + intros. intros eps. + specialize (H eps) as [N Nmaj]. + exists (N+k)%nat. intros n H. + destruct (Nat.le_exists_sub k n). + apply (le_trans _ (N + k)). 2: exact H. + apply (le_trans _ (0 + k)). apply le_refl. + rewrite <- Nat.add_le_mono_r. apply le_0_n. + destruct H0. + subst n. apply Nmaj. unfold ge in H. + rewrite <- Nat.add_le_mono_r in H. exact H. +Qed. + +Lemma CR_cv_shift' : + forall {R : ConstructiveReals} f k l, + CR_cv R f l -> CR_cv R (fun n => f (n + k)%nat) l. +Proof. + intros R f' k l cvf eps; destruct (cvf eps) as [N Pn]. + exists N; intros n nN; apply Pn; auto with arith. +Qed. + +Lemma series_cv_shift : + forall {R : ConstructiveReals} (f : nat -> CRcarrier R) k l, + series_cv (fun n => f (S k + n)%nat) l + -> series_cv f (l + CRsum f k). +Proof. + intros. intro p. specialize (H p) as [n nmaj]. + exists (S k+n)%nat. intros. destruct (Nat.le_exists_sub (S k) i). + apply (le_trans _ (S k + 0)). rewrite Nat.add_0_r. apply le_refl. + apply (le_trans _ (S k + n)). apply Nat.add_le_mono_l, le_0_n. + exact H. destruct H0. subst i. + rewrite Nat.add_comm in H. rewrite <- Nat.add_le_mono_r in H. + specialize (nmaj x H). unfold CRminus. + rewrite Nat.add_comm, (sum_assoc f k x). + setoid_replace (CRsum f k + CRsum (fun k0 : nat => f (S k + k0)%nat) x - (l + CRsum f k)) + with (CRsum (fun k0 : nat => f (S k + k0)%nat) x - l). + exact nmaj. unfold CRminus. rewrite (CRplus_comm (CRsum f k)). + rewrite CRplus_assoc. apply CRplus_morph. reflexivity. + rewrite CRplus_comm, CRopp_plus_distr, CRplus_assoc. + rewrite CRplus_opp_l, CRplus_0_r. reflexivity. +Qed. + +Lemma series_cv_shift' : forall {R : ConstructiveReals} + (un : nat -> CRcarrier R) (s : CRcarrier R) (shift : nat), + series_cv un s + -> series_cv (fun n => un (n+shift)%nat) + (s - match shift with + | O => 0 + | S p => CRsum un p + end). +Proof. + intros. destruct shift as [|p]. + - unfold CRminus. rewrite CRopp_0. rewrite CRplus_0_r. + apply (series_cv_eq un). intros. + rewrite plus_0_r. reflexivity. apply H. + - apply (CR_cv_eq _ (fun n => CRsum un (n + S p) - CRsum un p)). + intros. rewrite plus_comm. unfold CRminus. + rewrite sum_assoc. simpl. rewrite CRplus_comm, <- CRplus_assoc. + rewrite CRplus_opp_l, CRplus_0_l. + apply CRsum_eq. intros. rewrite (plus_comm i). reflexivity. + apply CR_cv_plus. apply (CR_cv_shift' _ (S p) _ H). + intros n. exists (Pos.to_nat n). intros. + unfold CRminus. simpl. + rewrite CRopp_involutive, CRplus_opp_l. rewrite CRabs_right. + rewrite <- CR_of_Q_zero. apply CR_of_Q_le. discriminate. apply CRle_refl. +Qed. diff --git a/theories/Reals/Abstract/ConstructiveReals.v b/theories/Reals/Abstract/ConstructiveReals.v new file mode 100644 index 0000000000..d91fd1183a --- /dev/null +++ b/theories/Reals/Abstract/ConstructiveReals.v @@ -0,0 +1,1149 @@ +(************************************************************************) +(* * The Coq Proof Assistant / The Coq Development Team *) +(* v * INRIA, CNRS and contributors - Copyright 1999-2019 *) +(* <O___,, * (see CREDITS file for the list of authors) *) +(* \VV/ **************************************************************) +(* // * This file is distributed under the terms of the *) +(* * GNU Lesser General Public License Version 2.1 *) +(* * (see LICENSE file for the text of the license) *) +(************************************************************************) +(************************************************************************) + +(** An interface for constructive and computable real numbers. + All of its instances are isomorphic (see file ConstructiveRealsMorphisms). + For example it is implemented by the Cauchy reals in file + ConstructivecauchyReals and also implemented by the sumbool-based + Dedekind reals defined by + +Structure R := { + (* The cuts are represented as propositional functions, rather than subsets, + as there are no subsets in type theory. *) + lower : Q -> Prop; + upper : Q -> Prop; + (* The cuts respect equality on Q. *) + lower_proper : Proper (Qeq ==> iff) lower; + upper_proper : Proper (Qeq ==> iff) upper; + (* The cuts are inhabited. *) + lower_bound : { q : Q | lower q }; + upper_bound : { r : Q | upper r }; + (* The lower cut is a lower set. *) + lower_lower : forall q r, q < r -> lower r -> lower q; + (* The lower cut is open. *) + lower_open : forall q, lower q -> exists r, q < r /\ lower r; + (* The upper cut is an upper set. *) + upper_upper : forall q r, q < r -> upper q -> upper r; + (* The upper cut is open. *) + upper_open : forall r, upper r -> exists q, q < r /\ upper q; + (* The cuts are disjoint. *) + disjoint : forall q, ~ (lower q /\ upper q); + (* There is no gap between the cuts. *) + located : forall q r, q < r -> { lower q } + { upper r } +}. + + see github.com/andrejbauer/dedekind-reals for the Prop-based + version of those Dedekind reals (although Prop fails to make + them an instance of ConstructiveReals). + + Any computation about constructive reals can be worked + in the fastest instance for it; we then transport the results + to all other instances by the isomorphisms. This way of working + is different from the usual interfaces, where we would rather + prove things abstractly, by quantifying universally on the instance. + + The functions of ConstructiveReals do not have a direct impact + on performance, because algorithms will be extracted from instances, + and because fast ConstructiveReals morphisms should be coded + manually. However, since instances are forced to implement + those functions, it is probable that they will also use them + in their algorithms. So those functions hint at what we think + will yield fast and small extracted programs. + + Constructive reals are setoids, which custom equality is defined as + x == y iff (x <= y /\ y <= x). + It is hard to quotient constructively to get the Leibniz equality + on the real numbers. In "Sheaves in Geometry and Logic", + MacLane and Moerdijk show a topos in which all functions R -> Z + are constant. Consequently all functions R -> Q are constant and + it is not possible to approximate real numbers by rational numbers. *) + + +Require Import QArith Qabs Qround. + +Definition isLinearOrder {X : Set} (Xlt : X -> X -> Set) : Set + := (forall x y:X, Xlt x y -> Xlt y x -> False) + * (forall x y z : X, Xlt x y -> Xlt y z -> Xlt x z) + * (forall x y z : X, Xlt x z -> Xlt x y + Xlt y z). + +Structure ConstructiveReals : Type := + { + CRcarrier : Set; + + (* Put this order relation in sort Set rather than Prop, + to allow the definition of fast ConstructiveReals morphisms. + For example, the Cauchy reals do store information in + the proofs of CRlt, which is used in algorithms in sort Set. *) + CRlt : CRcarrier -> CRcarrier -> Set; + CRltLinear : isLinearOrder CRlt; + + CRle (x y : CRcarrier) := CRlt y x -> False; + CReq (x y : CRcarrier) := CRle y x /\ CRle x y; + CRapart (x y : CRcarrier) := sum (CRlt x y) (CRlt y x); + + (* The propositional truncation of CRlt. It facilitates proofs + when computations are not considered important, for example in + classical reals with extra logical axioms. *) + CRltProp : CRcarrier -> CRcarrier -> Prop; + (* This choice algorithm can be slow, keep it for the classical + quotient of the reals, where computations are blocked by + axioms like LPO. *) + CRltEpsilon : forall x y : CRcarrier, CRltProp x y -> CRlt x y; + CRltForget : forall x y : CRcarrier, CRlt x y -> CRltProp x y; + CRltDisjunctEpsilon : forall a b c d : CRcarrier, + (CRltProp a b \/ CRltProp c d) -> CRlt a b + CRlt c d; + + (* Constants *) + CRzero : CRcarrier; + CRone : CRcarrier; + + (* Addition and multiplication *) + CRplus : CRcarrier -> CRcarrier -> CRcarrier; + CRopp : CRcarrier -> CRcarrier; (* Computable opposite, + stronger than Prop-existence of opposite *) + CRmult : CRcarrier -> CRcarrier -> CRcarrier; + + CRisRing : ring_theory CRzero CRone CRplus CRmult + (fun x y => CRplus x (CRopp y)) CRopp CReq; + CRisRingExt : ring_eq_ext CRplus CRmult CRopp CReq; + + (* Compatibility with order *) + CRzero_lt_one : CRlt CRzero CRone; (* 0 # 1 would only allow 0 < 1 because + of Fmult_lt_0_compat so request 0 < 1 directly. *) + CRplus_lt_compat_l : forall r r1 r2 : CRcarrier, + CRlt r1 r2 -> CRlt (CRplus r r1) (CRplus r r2); + CRplus_lt_reg_l : forall r r1 r2 : CRcarrier, + CRlt (CRplus r r1) (CRplus r r2) -> CRlt r1 r2; + CRmult_lt_0_compat : forall x y : CRcarrier, + CRlt CRzero x -> CRlt CRzero y -> CRlt CRzero (CRmult x y); + + (* A constructive total inverse function on F would need to be continuous, + which is impossible because we cannot connect plus and minus infinities. + Therefore it has to be a partial function, defined on non zero elements. + For this reason we cannot use Coq's field_theory and field tactic. + + To implement Finv by Cauchy sequences we need orderAppart, + ~orderEq is not enough. *) + CRinv : forall x : CRcarrier, CRapart x CRzero -> CRcarrier; + CRinv_l : forall (r:CRcarrier) (rnz : CRapart r CRzero), + CReq (CRmult (CRinv r rnz) r) CRone; + CRinv_0_lt_compat : forall (r : CRcarrier) (rnz : CRapart r CRzero), + CRlt CRzero r -> CRlt CRzero (CRinv r rnz); + + (* The initial field morphism (in characteristic zero). + The abstract definition by iteration of addition is + probably the slowest. Let each instance implement + a faster (and often simpler) version. *) + CR_of_Q : Q -> CRcarrier; + CR_of_Q_plus : forall q r : Q, CReq (CR_of_Q (q+r)) + (CRplus (CR_of_Q q) (CR_of_Q r)); + CR_of_Q_mult : forall q r : Q, CReq (CR_of_Q (q*r)) + (CRmult (CR_of_Q q) (CR_of_Q r)); + CR_of_Q_one : CReq (CR_of_Q 1) CRone; + CR_of_Q_lt : forall q r : Q, + Qlt q r -> CRlt (CR_of_Q q) (CR_of_Q r); + lt_CR_of_Q : forall q r : Q, + CRlt (CR_of_Q q) (CR_of_Q r) -> Qlt q r; + + (* This function is very fast in both the Cauchy and Dedekind + instances, because this rational number q is almost what + the proof of CRlt x y contains. + This function is also the heart of the computation of + constructive real numbers : it approximates x to any + requested precision y. *) + CR_Q_dense : forall x y : CRcarrier, CRlt x y -> + { q : Q & prod (CRlt x (CR_of_Q q)) + (CRlt (CR_of_Q q) y) }; + CR_archimedean : forall x : CRcarrier, + { n : positive & CRlt x (CR_of_Q (Z.pos n # 1)) }; + + CRminus (x y : CRcarrier) : CRcarrier + := CRplus x (CRopp y); + + (* Absolute value, CRabs x is the least upper bound + of the pair x, -x. *) + CRabs : CRcarrier -> CRcarrier; + CRabs_def : forall x y : CRcarrier, + (CRle x y /\ CRle (CRopp x) y) + <-> CRle (CRabs x) y; + + (* Definitions of convergence and Cauchy-ness. The formulas + with orderLe or CRlt are logically equivalent, the choice of + orderLe in sort Prop is a question of performance. + It is very rare to turn back to the strict order to + define functions in sort Set, so we prefer to discard + those proofs during extraction. And even in those rare cases, + it is easy to divide epsilon by 2 for example. *) + CR_cv (un : nat -> CRcarrier) (l : CRcarrier) : Set + := forall p:positive, + { n : nat | forall i:nat, le n i + -> CRle (CRabs (CRminus (un i) l)) + (CR_of_Q (1#p)) }; + CR_cauchy (un : nat -> CRcarrier) : Set + := forall p : positive, + { n : nat | forall i j:nat, le n i -> le n j + -> CRle (CRabs (CRminus (un i) (un j))) + (CR_of_Q (1#p)) }; + + (* For the Cauchy reals, this algorithm consists in building + a Cauchy sequence of rationals un : nat -> Q that has + the same limit as xn. For each n:nat, un n is a 1/n + rational approximation of a point of xn that has converged + within 1/n. *) + CR_complete : + forall xn : (nat -> CRcarrier), + CR_cauchy xn -> { l : CRcarrier & CR_cv xn l }; + }. + +Declare Scope ConstructiveReals. + +Delimit Scope ConstructiveReals with ConstructiveReals. + +Notation "x < y" := (CRlt _ x y) : ConstructiveReals. +Notation "x <= y" := (CRle _ x y) : ConstructiveReals. +Notation "x <= y <= z" := (CRle _ x y /\ CRle _ y z) : ConstructiveReals. +Notation "x < y < z" := (prod (CRlt _ x y) (CRlt _ y z)) : ConstructiveReals. +Notation "x == y" := (CReq _ x y) : ConstructiveReals. +Notation "x ≶ y" := (CRapart _ x y) (at level 70, no associativity) : ConstructiveReals. +Notation "0" := (CRzero _) : ConstructiveReals. +Notation "1" := (CRone _) : ConstructiveReals. +Notation "x + y" := (CRplus _ x y) : ConstructiveReals. +Notation "- x" := (CRopp _ x) : ConstructiveReals. +Notation "x - y" := (CRminus _ x y) : ConstructiveReals. +Notation "x * y" := (CRmult _ x y) : ConstructiveReals. +Notation "/ x" := (CRinv _ x) : ConstructiveReals. + +Local Open Scope ConstructiveReals. + +Lemma CRlt_asym : forall {R : ConstructiveReals} (x y : CRcarrier R), + x < y -> x <= y. +Proof. + intros. intro H0. destruct (CRltLinear R), p. + apply (f x y); assumption. +Qed. + +Lemma CRlt_proper + : forall R : ConstructiveReals, + CMorphisms.Proper + (CMorphisms.respectful (CReq R) + (CMorphisms.respectful (CReq R) CRelationClasses.iffT)) (CRlt R). +Proof. + intros R x y H x0 y0 H0. destruct H, H0. + destruct (CRltLinear R). split. + - intro. destruct (s x y x0). assumption. + contradiction. destruct (s y y0 x0). + assumption. assumption. contradiction. + - intro. destruct (s y x y0). assumption. + contradiction. destruct (s x x0 y0). + assumption. assumption. contradiction. +Qed. + +Lemma CRle_refl : forall {R : ConstructiveReals} (x : CRcarrier R), + x <= x. +Proof. + intros. intro H. destruct (CRltLinear R), p. + exact (f x x H H). +Qed. + +Lemma CRle_lt_trans : forall {R : ConstructiveReals} (r1 r2 r3 : CRcarrier R), + r1 <= r2 -> r2 < r3 -> r1 < r3. +Proof. + intros. destruct (CRltLinear R). + destruct (s r2 r1 r3 H0). contradiction. apply c. +Qed. + +Lemma CRlt_le_trans : forall {R : ConstructiveReals} (r1 r2 r3 : CRcarrier R), + r1 < r2 -> r2 <= r3 -> r1 < r3. +Proof. + intros. destruct (CRltLinear R). + destruct (s r1 r3 r2 H). apply c. contradiction. +Qed. + +Lemma CRle_trans : forall {R : ConstructiveReals} (x y z : CRcarrier R), + x <= y -> y <= z -> x <= z. +Proof. + intros. intro abs. apply H0. + apply (CRlt_le_trans _ x); assumption. +Qed. + +Lemma CRlt_trans : forall {R : ConstructiveReals} (x y z : CRcarrier R), + x < y -> y < z -> x < z. +Proof. + intros. apply (CRlt_le_trans _ y _ H). + apply CRlt_asym. exact H0. +Defined. + +Lemma CRlt_trans_flip : forall {R : ConstructiveReals} (x y z : CRcarrier R), + y < z -> x < y -> x < z. +Proof. + intros. apply (CRlt_le_trans _ y). exact H0. + apply CRlt_asym. exact H. +Defined. + +Lemma CReq_refl : forall {R : ConstructiveReals} (x : CRcarrier R), + x == x. +Proof. + split; apply CRle_refl. +Qed. + +Lemma CReq_sym : forall {R : ConstructiveReals} (x y : CRcarrier R), + x == y -> y == x. +Proof. + intros. destruct H. split; intro abs; contradiction. +Qed. + +Lemma CReq_trans : forall {R : ConstructiveReals} (x y z : CRcarrier R), + x == y -> y == z -> x == z. +Proof. + intros. destruct H,H0. destruct (CRltLinear R), p. split. + - intro abs. destruct (s _ y _ abs); contradiction. + - intro abs. destruct (s _ y _ abs); contradiction. +Qed. + +Add Parametric Relation {R : ConstructiveReals} : (CRcarrier R) (CReq R) + reflexivity proved by (CReq_refl) + symmetry proved by (CReq_sym) + transitivity proved by (CReq_trans) + as CReq_rel. + +Instance CReq_relT : forall {R : ConstructiveReals}, + CRelationClasses.Equivalence (CReq R). +Proof. + split. exact CReq_refl. exact CReq_sym. exact CReq_trans. +Qed. + +Instance CRlt_morph + : forall {R : ConstructiveReals}, CMorphisms.Proper + (CMorphisms.respectful (CReq R) (CMorphisms.respectful (CReq R) CRelationClasses.iffT)) (CRlt R). +Proof. + intros R x y H x0 y0 H0. destruct H, H0. split. + - intro. destruct (CRltLinear R). destruct (s x y x0). assumption. + contradiction. destruct (s y y0 x0). + assumption. assumption. contradiction. + - intro. destruct (CRltLinear R). destruct (s y x y0). assumption. + contradiction. destruct (s x x0 y0). + assumption. assumption. contradiction. +Qed. + +Add Parametric Morphism {R : ConstructiveReals} : (CRle R) + with signature CReq R ==> CReq R ==> iff + as CRle_morph. +Proof. + intros. split. + - intros H1 H2. unfold CRle in H1. + rewrite <- H0 in H2. rewrite <- H in H2. contradiction. + - intros H1 H2. unfold CRle in H1. + rewrite H0 in H2. rewrite H in H2. contradiction. +Qed. + +Lemma CRplus_0_l : forall {R : ConstructiveReals} (x : CRcarrier R), + 0 + x == x. +Proof. + intros. destruct (CRisRing R). apply Radd_0_l. +Qed. + +Lemma CRplus_0_r : forall {R : ConstructiveReals} (x : CRcarrier R), + x + 0 == x. +Proof. + intros. destruct (CRisRing R). + transitivity (0 + x). + apply Radd_comm. apply Radd_0_l. +Qed. + +Lemma CRplus_opp_l : forall {R : ConstructiveReals} (x : CRcarrier R), + - x + x == 0. +Proof. + intros. destruct (CRisRing R). + transitivity (x + - x). + apply Radd_comm. apply Ropp_def. +Qed. + +Lemma CRplus_opp_r : forall {R : ConstructiveReals} (x : CRcarrier R), + x + - x == 0. +Proof. + intros. destruct (CRisRing R). apply Ropp_def. +Qed. + +Lemma CRopp_0 : forall {R : ConstructiveReals}, + CRopp R 0 == 0. +Proof. + intros. rewrite <- CRplus_0_r, CRplus_opp_l. + reflexivity. +Qed. + +Lemma CRplus_lt_compat_r : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + r1 < r2 -> r1 + r < r2 + r. +Proof. + intros. destruct (CRisRing R). + apply (CRlt_proper R (CRplus R r r1) (CRplus R r1 r) (Radd_comm _ _) + (CRplus R r2 r) (CRplus R r2 r)). + apply CReq_refl. + apply (CRlt_proper R _ _ (CReq_refl _) _ (CRplus R r r2)). + apply Radd_comm. apply CRplus_lt_compat_l. exact H. +Qed. + +Lemma CRplus_lt_reg_r : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + r1 + r < r2 + r -> r1 < r2. +Proof. + intros. destruct (CRisRing R). + apply (CRlt_proper R (CRplus R r r1) (CRplus R r1 r) (Radd_comm _ _) + (CRplus R r2 r) (CRplus R r2 r)) in H. + 2: apply CReq_refl. + apply (CRlt_proper R _ _ (CReq_refl _) _ (CRplus R r r2)) in H. + apply CRplus_lt_reg_l in H. exact H. + apply Radd_comm. +Qed. + +Lemma CRplus_le_compat_l : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + r1 <= r2 -> r + r1 <= r + r2. +Proof. + intros. intros abs. apply CRplus_lt_reg_l in abs. apply H. exact abs. +Qed. + +Lemma CRplus_le_compat_r : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + r1 <= r2 -> r1 + r <= r2 + r. +Proof. + intros. intros abs. apply CRplus_lt_reg_r in abs. apply H. exact abs. +Qed. + +Lemma CRplus_le_compat : forall {R : ConstructiveReals} (r1 r2 r3 r4 : CRcarrier R), + r1 <= r2 -> r3 <= r4 -> r1 + r3 <= r2 + r4. +Proof. + intros. apply (CRle_trans _ (CRplus R r2 r3)). + apply CRplus_le_compat_r, H. apply CRplus_le_compat_l, H0. +Qed. + +Lemma CRle_minus : forall {R : ConstructiveReals} (x y : CRcarrier R), + x <= y -> 0 <= y - x. +Proof. + intros. rewrite <- (CRplus_opp_r x). + apply CRplus_le_compat_r. exact H. +Qed. + +Lemma CRplus_le_reg_l : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + r + r1 <= r + r2 -> r1 <= r2. +Proof. + intros. intro abs. apply H. clear H. + apply CRplus_lt_compat_l. exact abs. +Qed. + +Lemma CRplus_le_reg_r : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + r1 + r <= r2 + r -> r1 <= r2. +Proof. + intros. intro abs. apply H. clear H. + apply CRplus_lt_compat_r. exact abs. +Qed. + +Lemma CRplus_lt_le_compat : + forall {R : ConstructiveReals} (r1 r2 r3 r4 : CRcarrier R), + r1 < r2 + -> r3 <= r4 + -> r1 + r3 < r2 + r4. +Proof. + intros. apply (CRlt_le_trans _ (CRplus R r2 r3)). + apply CRplus_lt_compat_r. exact H. intro abs. + apply CRplus_lt_reg_l in abs. contradiction. +Qed. + +Lemma CRplus_le_lt_compat : + forall {R : ConstructiveReals} (r1 r2 r3 r4 : CRcarrier R), + r1 <= r2 + -> r3 < r4 + -> r1 + r3 < r2 + r4. +Proof. + intros. apply (CRle_lt_trans _ (CRplus R r2 r3)). + apply CRplus_le_compat_r. exact H. + apply CRplus_lt_compat_l. exact H0. +Qed. + +Lemma CRplus_eq_reg_l : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + r + r1 == r + r2 -> r1 == r2. +Proof. + intros. + destruct (CRisRingExt R). clear Rmul_ext Ropp_ext. + pose proof (Radd_ext + (CRopp R r) (CRopp R r) (CReq_refl _) + _ _ H). + destruct (CRisRing R). + apply (CReq_trans r1) in H0. + apply (CReq_trans _ _ _ H0). + transitivity ((- r + r) + r2). + apply Radd_assoc. transitivity (0 + r2). + apply Radd_ext. apply CRplus_opp_l. apply CReq_refl. + apply Radd_0_l. apply CReq_sym. + transitivity (- r + r + r1). + apply Radd_assoc. + transitivity (0 + r1). + apply Radd_ext. apply CRplus_opp_l. apply CReq_refl. + apply Radd_0_l. +Qed. + +Lemma CRplus_eq_reg_r : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + r1 + r == r2 + r -> r1 == r2. +Proof. + intros. apply (CRplus_eq_reg_l r). + transitivity (r1 + r). apply (Radd_comm (CRisRing R)). + transitivity (r2 + r). + exact H. apply (Radd_comm (CRisRing R)). +Qed. + +Lemma CRplus_assoc : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + r + r1 + r2 == r + (r1 + r2). +Proof. + intros. symmetry. apply (Radd_assoc (CRisRing R)). +Qed. + +Lemma CRplus_comm : forall {R : ConstructiveReals} (r1 r2 : CRcarrier R), + r1 + r2 == r2 + r1. +Proof. + intros. apply (Radd_comm (CRisRing R)). +Qed. + +Add Parametric Morphism {R : ConstructiveReals} : (CRplus R) + with signature CReq R ==> CReq R ==> CReq R + as CRplus_morph. +Proof. + apply (CRisRingExt R). +Qed. + +Add Parametric Morphism {R : ConstructiveReals} : (CRopp R) + with signature CReq R ==> CReq R + as CRopp_morph. +Proof. + apply (CRisRingExt R). +Qed. + +Add Parametric Morphism {R : ConstructiveReals} : (CRmult R) + with signature CReq R ==> CReq R ==> CReq R + as CRmult_morph. +Proof. + apply (CRisRingExt R). +Qed. + +Instance CRplus_morph_T + : forall {R : ConstructiveReals}, CMorphisms.Proper + (CMorphisms.respectful (CReq R) (CMorphisms.respectful (CReq R) (CReq R))) (CRplus R). +Proof. + intros R x y H z t H1. apply CRplus_morph; assumption. +Qed. + +Instance CRmult_morph_T + : forall {R : ConstructiveReals}, CMorphisms.Proper + (CMorphisms.respectful (CReq R) (CMorphisms.respectful (CReq R) (CReq R))) (CRmult R). +Proof. + intros R x y H z t H1. apply CRmult_morph; assumption. +Qed. + +Instance CRopp_morph_T + : forall {R : ConstructiveReals}, CMorphisms.Proper + (CMorphisms.respectful (CReq R) (CReq R)) (CRopp R). +Proof. + apply CRisRingExt. +Qed. + +Add Parametric Morphism {R : ConstructiveReals} : (CRminus R) + with signature (CReq R) ==> (CReq R) ==> (CReq R) + as CRminus_morph. +Proof. + intros. unfold CRminus. rewrite H,H0. reflexivity. +Qed. + +Instance CRminus_morph_T + : forall {R : ConstructiveReals}, CMorphisms.Proper + (CMorphisms.respectful (CReq R) (CMorphisms.respectful (CReq R) (CReq R))) (CRminus R). +Proof. + intros R x y exy z t ezt. unfold CRminus. rewrite exy,ezt. reflexivity. +Qed. + +Lemma CRopp_involutive : forall {R : ConstructiveReals} (r : CRcarrier R), + - - r == r. +Proof. + intros. apply (CRplus_eq_reg_l (CRopp R r)). + transitivity (CRzero R). apply CRisRing. + apply CReq_sym. transitivity (r + - r). + apply CRisRing. apply CRisRing. +Qed. + +Lemma CRopp_gt_lt_contravar + : forall {R : ConstructiveReals} (r1 r2 : CRcarrier R), + r2 < r1 -> - r1 < - r2. +Proof. + intros. apply (CRplus_lt_reg_l R r1). + destruct (CRisRing R). + apply (CRle_lt_trans _ (CRzero R)). apply Ropp_def. + apply (CRplus_lt_compat_l R (CRopp R r2)) in H. + apply (CRle_lt_trans _ (CRplus R (CRopp R r2) r2)). + apply (CRle_trans _ (CRplus R r2 (CRopp R r2))). + destruct (Ropp_def r2). exact H0. + destruct (Radd_comm r2 (CRopp R r2)). exact H1. + apply (CRlt_le_trans _ _ _ H). + destruct (Radd_comm r1 (CRopp R r2)). exact H0. +Qed. + +Lemma CRopp_lt_cancel : forall {R : ConstructiveReals} (r1 r2 : CRcarrier R), + - r2 < - r1 -> r1 < r2. +Proof. + intros. apply (CRplus_lt_compat_r r1) in H. + rewrite (CRplus_opp_l r1) in H. + apply (CRplus_lt_compat_l R r2) in H. + rewrite CRplus_0_r, (Radd_assoc (CRisRing R)) in H. + rewrite CRplus_opp_r, (Radd_0_l (CRisRing R)) in H. + exact H. +Qed. + +Lemma CRopp_ge_le_contravar + : forall {R : ConstructiveReals} (r1 r2 : CRcarrier R), + r2 <= r1 -> - r1 <= - r2. +Proof. + intros. intros abs. apply CRopp_lt_cancel in abs. contradiction. +Qed. + +Lemma CRopp_plus_distr : forall {R : ConstructiveReals} (r1 r2 : CRcarrier R), + - (r1 + r2) == - r1 + - r2. +Proof. + intros. destruct (CRisRing R), (CRisRingExt R). + apply (CRplus_eq_reg_l (CRplus R r1 r2)). + transitivity (CRzero R). apply Ropp_def. + transitivity (r2 + r1 + (-r1 + -r2)). + transitivity (r2 + (r1 + (-r1 + -r2))). + transitivity (r2 + - r2). + apply CReq_sym. apply Ropp_def. apply Radd_ext. + apply CReq_refl. + transitivity (CRzero R + - r2). + apply CReq_sym, Radd_0_l. + transitivity (r1 + - r1 + - r2). + apply Radd_ext. 2: apply CReq_refl. apply CReq_sym, Ropp_def. + apply CReq_sym, Radd_assoc. apply Radd_assoc. + apply Radd_ext. 2: apply CReq_refl. apply Radd_comm. +Qed. + +Lemma CRmult_1_l : forall {R : ConstructiveReals} (r : CRcarrier R), + 1 * r == r. +Proof. + intros. destruct (CRisRing R). apply Rmul_1_l. +Qed. + +Lemma CRmult_1_r : forall {R : ConstructiveReals} (x : CRcarrier R), + x * 1 == x. +Proof. + intros. destruct (CRisRing R). transitivity (CRmult R 1 x). + apply Rmul_comm. apply Rmul_1_l. +Qed. + +Lemma CRmult_assoc : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + r * r1 * r2 == r * (r1 * r2). +Proof. + intros. symmetry. apply (Rmul_assoc (CRisRing R)). +Qed. + +Lemma CRmult_comm : forall {R : ConstructiveReals} (r s : CRcarrier R), + r * s == s * r. +Proof. + intros. rewrite (Rmul_comm (CRisRing R) r). reflexivity. +Qed. + +Lemma CRmult_plus_distr_l : forall {R : ConstructiveReals} (r1 r2 r3 : CRcarrier R), + r1 * (r2 + r3) == (r1 * r2) + (r1 * r3). +Proof. + intros. destruct (CRisRing R). + transitivity ((r2 + r3) * r1). + apply Rmul_comm. + transitivity ((r2 * r1) + (r3 * r1)). + apply Rdistr_l. + transitivity ((r1 * r2) + (r3 * r1)). + destruct (CRisRingExt R). apply Radd_ext. + apply Rmul_comm. apply CReq_refl. + destruct (CRisRingExt R). apply Radd_ext. + apply CReq_refl. apply Rmul_comm. +Qed. + +Lemma CRmult_plus_distr_r : forall {R : ConstructiveReals} (r1 r2 r3 : CRcarrier R), + (r2 + r3) * r1 == (r2 * r1) + (r3 * r1). +Proof. + intros. do 3 rewrite <- (CRmult_comm r1). + apply CRmult_plus_distr_l. +Qed. + +(* x == x+x -> x == 0 *) +Lemma CRzero_double : forall {R : ConstructiveReals} (x : CRcarrier R), + x == x + x -> x == 0. +Proof. + intros. + apply (CRplus_eq_reg_l x), CReq_sym. transitivity x. + apply CRplus_0_r. exact H. +Qed. + +Lemma CRmult_0_r : forall {R : ConstructiveReals} (x : CRcarrier R), + x * 0 == 0. +Proof. + intros. apply CRzero_double. + transitivity (x * (0 + 0)). + destruct (CRisRingExt R). apply Rmul_ext. apply CReq_refl. + apply CReq_sym, CRplus_0_r. + destruct (CRisRing R). apply CRmult_plus_distr_l. +Qed. + +Lemma CRmult_0_l : forall {R : ConstructiveReals} (r : CRcarrier R), + 0 * r == 0. +Proof. + intros. rewrite CRmult_comm. apply CRmult_0_r. +Qed. + +Lemma CRopp_mult_distr_r : forall {R : ConstructiveReals} (r1 r2 : CRcarrier R), + - (r1 * r2) == r1 * (- r2). +Proof. + intros. apply (CRplus_eq_reg_l (CRmult R r1 r2)). + destruct (CRisRing R). transitivity (CRzero R). apply Ropp_def. + transitivity (r1 * (r2 + - r2)). + 2: apply CRmult_plus_distr_l. + transitivity (r1 * 0). + apply CReq_sym, CRmult_0_r. + destruct (CRisRingExt R). apply Rmul_ext. apply CReq_refl. + apply CReq_sym, Ropp_def. +Qed. + +Lemma CRopp_mult_distr_l : forall {R : ConstructiveReals} (r1 r2 : CRcarrier R), + - (r1 * r2) == (- r1) * r2. +Proof. + intros. transitivity (r2 * - r1). + transitivity (- (r2 * r1)). + apply (Ropp_ext (CRisRingExt R)). + apply CReq_sym, (Rmul_comm (CRisRing R)). + apply CRopp_mult_distr_r. + apply CReq_sym, (Rmul_comm (CRisRing R)). +Qed. + +Lemma CRmult_lt_compat_r : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + 0 < r -> r1 < r2 -> r1 * r < r2 * r. +Proof. + intros. apply (CRplus_lt_reg_r (CRopp R (CRmult R r1 r))). + apply (CRle_lt_trans _ (CRzero R)). + apply (Ropp_def (CRisRing R)). + apply (CRlt_le_trans _ (CRplus R (CRmult R r2 r) (CRmult R (CRopp R r1) r))). + apply (CRlt_le_trans _ (CRmult R (CRplus R r2 (CRopp R r1)) r)). + apply CRmult_lt_0_compat. 2: exact H. + apply (CRplus_lt_reg_r r1). + apply (CRle_lt_trans _ r1). apply (Radd_0_l (CRisRing R)). + apply (CRlt_le_trans _ r2 _ H0). + apply (CRle_trans _ (CRplus R r2 (CRplus R (CRopp R r1) r1))). + apply (CRle_trans _ (CRplus R r2 (CRzero R))). + destruct (CRplus_0_r r2). exact H1. + apply CRplus_le_compat_l. destruct (CRplus_opp_l r1). exact H1. + destruct (Radd_assoc (CRisRing R) r2 (CRopp R r1) r1). exact H2. + destruct (CRisRing R). + destruct (Rdistr_l r2 (CRopp R r1) r). exact H2. + apply CRplus_le_compat_l. destruct (CRopp_mult_distr_l r1 r). + exact H1. +Qed. + +Lemma CRmult_lt_compat_l : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + 0 < r -> r1 < r2 -> r * r1 < r * r2. +Proof. + intros. do 2 rewrite (CRmult_comm r). + apply CRmult_lt_compat_r; assumption. +Qed. + +Lemma CRinv_r : forall {R : ConstructiveReals} (r:CRcarrier R) + (rnz : r ≶ (CRzero R)), + r * (/ r) rnz == 1. +Proof. + intros. transitivity ((/ r) rnz * r). + apply (CRisRing R). apply CRinv_l. +Qed. + +Lemma CRmult_lt_reg_r : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + 0 < r -> r1 * r < r2 * r -> r1 < r2. +Proof. + intros. apply (CRmult_lt_compat_r ((/ r) (inr H))) in H0. + 2: apply CRinv_0_lt_compat, H. + apply (CRle_lt_trans _ ((r1 * r) * ((/ r) (inr H)))). + - clear H0. apply (CRle_trans _ (CRmult R r1 (CRone R))). + destruct (CRmult_1_r r1). exact H0. + apply (CRle_trans _ (CRmult R r1 (CRmult R r ((/ r) (inr H))))). + destruct (Rmul_ext (CRisRingExt R) r1 r1 (CReq_refl r1) + (r * ((/ r) (inr H))) 1). + apply CRinv_r. exact H0. + destruct (Rmul_assoc (CRisRing R) r1 r ((/ r) (inr H))). exact H1. + - apply (CRlt_le_trans _ ((r2 * r) * ((/ r) (inr H)))). + exact H0. clear H0. + apply (CRle_trans _ (r2 * 1)). + 2: destruct (CRmult_1_r r2); exact H1. + apply (CRle_trans _ (r2 * (r * ((/ r) (inr H))))). + destruct (Rmul_assoc (CRisRing R) r2 r ((/ r) (inr H))). exact H0. + destruct (Rmul_ext (CRisRingExt R) r2 r2 (CReq_refl r2) + (r * ((/ r) (inr H))) (CRone R)). + apply CRinv_r. exact H1. +Qed. + +Lemma CRmult_lt_reg_l : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + 0 < r -> r * r1 < r * r2 -> r1 < r2. +Proof. + intros. + rewrite (Rmul_comm (CRisRing R) r r1) in H0. + rewrite (Rmul_comm (CRisRing R) r r2) in H0. + apply CRmult_lt_reg_r in H0. + exact H0. exact H. +Qed. + +Lemma CRmult_le_compat_l_half : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + 0 < r -> r1 <= r2 -> r * r1 <= r * r2. +Proof. + intros. intro abs. apply CRmult_lt_reg_l in abs. + contradiction. exact H. +Qed. + +Lemma CRmult_le_compat_r_half : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + 0 < r + -> r1 <= r2 + -> r1 * r <= r2 * r. +Proof. + intros. intro abs. apply CRmult_lt_reg_r in abs. + contradiction. exact H. +Qed. + +Lemma CRmult_eq_reg_r : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + 0 ≶ r + -> r1 * r == r2 * r + -> r1 == r2. +Proof. + intros. destruct H0,H. + - split. + + intro abs. apply H0. apply CRmult_lt_compat_r. + exact c. exact abs. + + intro abs. apply H1. apply CRmult_lt_compat_r. + exact c. exact abs. + - split. + + intro abs. apply H1. apply CRopp_lt_cancel. + apply (CRle_lt_trans _ (CRmult R r1 (CRopp R r))). + apply CRopp_mult_distr_r. + apply (CRlt_le_trans _ (CRmult R r2 (CRopp R r))). + 2: apply CRopp_mult_distr_r. + apply CRmult_lt_compat_r. 2: exact abs. + apply (CRplus_lt_reg_r r). apply (CRle_lt_trans _ r). + apply (Radd_0_l (CRisRing R)). + apply (CRlt_le_trans _ (CRzero R) _ c). + apply CRplus_opp_l. + + intro abs. apply H0. apply CRopp_lt_cancel. + apply (CRle_lt_trans _ (CRmult R r2 (CRopp R r))). + apply CRopp_mult_distr_r. + apply (CRlt_le_trans _ (CRmult R r1 (CRopp R r))). + 2: apply CRopp_mult_distr_r. + apply CRmult_lt_compat_r. 2: exact abs. + apply (CRplus_lt_reg_r r). apply (CRle_lt_trans _ r). + apply (Radd_0_l (CRisRing R)). + apply (CRlt_le_trans _ (CRzero R) _ c). + apply CRplus_opp_l. +Qed. + +Lemma CRinv_1 : forall {R : ConstructiveReals} (onz : CRapart R 1 0), + (/ 1) onz == 1. +Proof. + intros. rewrite <- (CRmult_1_r ((/ 1) onz)). + rewrite CRinv_l. reflexivity. +Qed. + +Lemma CRmult_eq_reg_l : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + r ≶ 0 + -> r * r1 == r * r2 + -> r1 == r2. +Proof. + intros. rewrite (Rmul_comm (CRisRing R)) in H0. + rewrite (Rmul_comm (CRisRing R) r) in H0. + apply CRmult_eq_reg_r in H0. exact H0. destruct H. + right. exact c. left. exact c. +Qed. + +Lemma CRinv_mult_distr : + forall {R : ConstructiveReals} (r1 r2 : CRcarrier R) + (r1nz : r1 ≶ 0) (r2nz : r2 ≶ 0) + (rmnz : (r1*r2) ≶ 0), + (/ (r1 * r2)) rmnz == (/ r1) r1nz * (/ r2) r2nz. +Proof. + intros. apply (CRmult_eq_reg_l r1). exact r1nz. + rewrite (Rmul_assoc (CRisRing R)). rewrite CRinv_r. rewrite CRmult_1_l. + apply (CRmult_eq_reg_l r2). exact r2nz. + rewrite CRinv_r. rewrite (Rmul_assoc (CRisRing R)). + rewrite (CRmult_comm r2 r1). rewrite CRinv_r. reflexivity. +Qed. + +Lemma CRinv_morph : forall {R : ConstructiveReals} (x y : CRcarrier R) + (rxnz : x ≶ 0) (rynz : y ≶ 0), + x == y + -> (/ x) rxnz == (/ y) rynz. +Proof. + intros. apply (CRmult_eq_reg_l x). exact rxnz. + rewrite CRinv_r, H, CRinv_r. reflexivity. +Qed. + +Lemma CRlt_minus : forall {R : ConstructiveReals} (x y : CRcarrier R), + x < y -> 0 < y - x. +Proof. + intros. rewrite <- (CRplus_opp_r x). + apply CRplus_lt_compat_r. exact H. +Qed. + +Lemma CR_of_Q_le : forall {R : ConstructiveReals} (r q : Q), + Qle r q + -> CR_of_Q R r <= CR_of_Q R q. +Proof. + intros. intro abs. apply lt_CR_of_Q in abs. + exact (Qlt_not_le _ _ abs H). +Qed. + +Add Parametric Morphism {R : ConstructiveReals} : (CR_of_Q R) + with signature Qeq ==> CReq R + as CR_of_Q_morph. +Proof. + split; apply CR_of_Q_le; rewrite H; apply Qle_refl. +Qed. + +Lemma eq_inject_Q : forall {R : ConstructiveReals} (q r : Q), + CR_of_Q R q == CR_of_Q R r -> Qeq q r. +Proof. + intros. destruct H. destruct (Q_dec q r). destruct s. + exfalso. apply (CR_of_Q_lt R q r) in q0. contradiction. + exfalso. apply (CR_of_Q_lt R r q) in q0. contradiction. exact q0. +Qed. + +Instance CR_of_Q_morph_T + : forall {R : ConstructiveReals}, CMorphisms.Proper + (CMorphisms.respectful Qeq (CReq R)) (CR_of_Q R). +Proof. + intros R x y H. apply CR_of_Q_morph; assumption. +Qed. + +Lemma CR_of_Q_zero : forall {R : ConstructiveReals}, + CR_of_Q R 0 == 0. +Proof. + intros. apply CRzero_double. + transitivity (CR_of_Q R (0+0)). apply CR_of_Q_morph. + reflexivity. apply CR_of_Q_plus. +Qed. + +Lemma CR_of_Q_opp : forall {R : ConstructiveReals} (q : Q), + CR_of_Q R (-q) == - CR_of_Q R q. +Proof. + intros. apply (CRplus_eq_reg_l (CR_of_Q R q)). + transitivity (CRzero R). + transitivity (CR_of_Q R (q-q)). + apply CReq_sym, CR_of_Q_plus. + transitivity (CR_of_Q R 0). + apply CR_of_Q_morph. ring. apply CR_of_Q_zero. + apply CReq_sym. apply (CRisRing R). +Qed. + +Lemma CR_of_Q_pos : forall {R : ConstructiveReals} (q:Q), + Qlt 0 q -> 0 < CR_of_Q R q. +Proof. + intros. apply (CRle_lt_trans _ (CR_of_Q R 0)). + apply CR_of_Q_zero. apply CR_of_Q_lt. exact H. +Qed. + +Lemma CR_of_Q_inv : forall {R : ConstructiveReals} (q : Q) (qPos : Qlt 0 q), + CR_of_Q R (/q) + == (/ CR_of_Q R q) (inr (CR_of_Q_pos q qPos)). +Proof. + intros. + apply (CRmult_eq_reg_l (CR_of_Q R q)). + right. apply CR_of_Q_pos, qPos. + rewrite CRinv_r, <- CR_of_Q_mult, <- CR_of_Q_one. + apply CR_of_Q_morph. field. intro abs. + rewrite abs in qPos. exact (Qlt_irrefl 0 qPos). +Qed. + +Lemma CRmult_le_0_compat : forall {R : ConstructiveReals} (a b : CRcarrier R), + 0 <= a -> 0 <= b -> 0 <= a * b. +Proof. + (* Limit of (a + 1/n)*b when n -> infty. *) + intros. intro abs. + assert (0 < -(a*b)) as epsPos. + { rewrite <- CRopp_0. apply CRopp_gt_lt_contravar. exact abs. } + destruct (CR_archimedean R (b * ((/ -(a*b)) (inr epsPos)))) + as [n maj]. + assert (0 < CR_of_Q R (Z.pos n #1)) as nPos. + { rewrite <- CR_of_Q_zero. apply CR_of_Q_lt. reflexivity. } + assert (b * (/ CR_of_Q R (Z.pos n #1)) (inr nPos) < -(a*b)). + { apply (CRmult_lt_reg_r (CR_of_Q R (Z.pos n #1))). apply nPos. + rewrite <- (Rmul_assoc (CRisRing R)), CRinv_l, CRmult_1_r. + apply (CRmult_lt_compat_r (-(a*b))) in maj. + rewrite CRmult_assoc, CRinv_l, CRmult_1_r in maj. + rewrite CRmult_comm. apply maj. apply epsPos. } + pose proof (CRmult_le_compat_l_half + (a + (/ CR_of_Q R (Z.pos n #1)) (inr nPos)) 0 b). + assert (0 + 0 < a + (/ CR_of_Q R (Z.pos n #1)) (inr nPos)). + { apply CRplus_le_lt_compat. apply H. apply CRinv_0_lt_compat. apply nPos. } + rewrite CRplus_0_l in H3. specialize (H2 H3 H0). + clear H3. rewrite CRmult_0_r in H2. + apply H2. clear H2. rewrite (Rdistr_l (CRisRing R)). + apply (CRplus_lt_compat_l R (a*b)) in H1. + rewrite CRplus_opp_r in H1. + rewrite (CRmult_comm ((/ CR_of_Q R (Z.pos n # 1)) (inr nPos))). + apply H1. +Qed. + +Lemma CRmult_le_compat_l : forall {R : ConstructiveReals} (r r1 r2:CRcarrier R), + 0 <= r -> r1 <= r2 -> r * r1 <= r * r2. +Proof. + intros. apply (CRplus_le_reg_r (-(r*r1))). + rewrite CRplus_opp_r, CRopp_mult_distr_r. + rewrite <- CRmult_plus_distr_l. + apply CRmult_le_0_compat. exact H. + apply (CRplus_le_reg_r r1). + rewrite CRplus_0_l, CRplus_assoc, CRplus_opp_l, CRplus_0_r. + exact H0. +Qed. + +Lemma CRmult_le_compat_r : forall {R : ConstructiveReals} (r r1 r2:CRcarrier R), + 0 <= r -> r1 <= r2 -> r1 * r <= r2 * r. +Proof. + intros. do 2 rewrite <- (CRmult_comm r). + apply CRmult_le_compat_l; assumption. +Qed. + +Lemma CRmult_pos_pos + : forall {R : ConstructiveReals} (x y : CRcarrier R), + 0 < x * y -> 0 <= x + -> 0 <= y -> 0 < x. +Proof. + intros. destruct (CRltLinear R). clear p. + specialize (s 0 x 1 (CRzero_lt_one R)) as [H2|H2]. + exact H2. apply CRlt_asym in H2. + apply (CRmult_le_compat_r y) in H2. + 2: exact H1. rewrite CRmult_1_l in H2. + apply (CRlt_le_trans _ _ _ H) in H2. + rewrite <- (CRmult_0_l y) in H. + apply CRmult_lt_reg_r in H. exact H. exact H2. +Qed. + +(* In particular x * y == 1 implies that 0 # x, 0 # y and + that x and y are inverses of each other. *) +Lemma CRmult_pos_appart_zero + : forall {R : ConstructiveReals} (x y : CRcarrier R), + 0 < x * y -> 0 ≶ x. +Proof. + intros. + (* Narrow cases to x < 1. *) + destruct (CRltLinear R). clear p. + pose proof (s 0 x 1 (CRzero_lt_one R)) as [H0|H0]. + left. exact H0. + (* In this case, linear order 0 y (x*y) decides. *) + destruct (s 0 y (x*y) H). + - left. rewrite <- (CRmult_0_l y) in H. apply CRmult_lt_reg_r in H. + exact H. exact c. + - right. apply CRopp_lt_cancel. rewrite CRopp_0. + apply (CRmult_pos_pos (-x) (-y)). + + rewrite <- CRopp_mult_distr_l, CRopp_mult_distr_r, CRopp_involutive. exact H. + + rewrite <- CRopp_0. apply CRopp_ge_le_contravar. + intro abs. rewrite <- (CRmult_0_r x) in H. + apply CRmult_lt_reg_l in H. rewrite <- (CRmult_1_l y) in c. + rewrite <- CRmult_assoc in c. apply CRmult_lt_reg_r in c. + rewrite CRmult_1_r in c. exact (CRlt_asym _ _ H0 c). + exact H. exact abs. + + intro abs. apply (CRmult_lt_compat_r y) in H0. + rewrite CRmult_1_l in H0. exact (CRlt_asym _ _ H0 c). + apply CRopp_lt_cancel. rewrite CRopp_0. exact abs. +Qed. + +Lemma CRmult_le_reg_l : + forall {R : ConstructiveReals} (x y z : CRcarrier R), + 0 < x -> x * y <= x * z -> y <= z. +Proof. + intros. intro abs. + apply (CRmult_lt_compat_l x) in abs. contradiction. + exact H. +Qed. + +Lemma CRmult_le_reg_r : + forall {R : ConstructiveReals} (x y z : CRcarrier R), + 0 < x -> y * x <= z * x -> y <= z. +Proof. + intros. intro abs. + apply (CRmult_lt_compat_r x) in abs. contradiction. exact H. +Qed. + +Definition CRup_nat {R : ConstructiveReals} (x : CRcarrier R) + : { n : nat & x < CR_of_Q R (Z.of_nat n #1) }. +Proof. + destruct (CR_archimedean R x). exists (Pos.to_nat x0). + rewrite positive_nat_Z. exact c. +Qed. + +Definition CRfloor {R : ConstructiveReals} (a : CRcarrier R) + : { p : Z & prod (CR_of_Q R (p#1) < a) + (a < CR_of_Q R (p#1) + CR_of_Q R 2) }. +Proof. + destruct (CR_Q_dense R (a - CR_of_Q R (1#2)) a) as [q qmaj]. + - apply (CRlt_le_trans _ (a-0)). apply CRplus_lt_compat_l. + apply CRopp_gt_lt_contravar. rewrite <- CR_of_Q_zero. + apply CR_of_Q_lt. reflexivity. + unfold CRminus. rewrite CRopp_0, CRplus_0_r. apply CRle_refl. + - exists (Qfloor q). destruct qmaj. split. + apply (CRle_lt_trans _ (CR_of_Q R q)). 2: exact c0. + apply CR_of_Q_le. apply Qfloor_le. + apply (CRlt_le_trans _ (CR_of_Q R q + CR_of_Q R (1#2))). + apply (CRplus_lt_compat_r (CR_of_Q R (1 # 2))) in c. + unfold CRminus in c. rewrite CRplus_assoc, CRplus_opp_l, CRplus_0_r in c. exact c. + rewrite (CR_of_Q_plus R 1 1), <- CRplus_assoc, <- (CR_of_Q_plus R _ 1). + apply CRplus_le_compat. apply CR_of_Q_le. + rewrite Qinv_plus_distr. apply Qlt_le_weak, Qlt_floor. + apply CR_of_Q_le. discriminate. +Qed. + +Lemma CRplus_appart_reg_l : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + (r + r1) ≶ (r + r2) -> r1 ≶ r2. +Proof. + intros. destruct H. + left. apply (CRplus_lt_reg_l R r), c. + right. apply (CRplus_lt_reg_l R r), c. +Qed. + +Lemma CRplus_appart_reg_r : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + (r1 + r) ≶ (r2 + r) -> r1 ≶ r2. +Proof. + intros. destruct H. + left. apply (CRplus_lt_reg_r r), c. + right. apply (CRplus_lt_reg_r r), c. +Qed. + +Lemma CRmult_appart_reg_l + : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + 0 < r -> (r * r1) ≶ (r * r2) -> r1 ≶ r2. +Proof. + intros. destruct H0. + left. exact (CRmult_lt_reg_l r _ _ H c). + right. exact (CRmult_lt_reg_l r _ _ H c). +Qed. + +Lemma CRmult_appart_reg_r + : forall {R : ConstructiveReals} (r r1 r2 : CRcarrier R), + 0 < r -> (r1 * r) ≶ (r2 * r) -> r1 ≶ r2. +Proof. + intros. destruct H0. + left. exact (CRmult_lt_reg_r r _ _ H c). + right. exact (CRmult_lt_reg_r r _ _ H c). +Qed. + +Instance CRapart_morph + : forall {R : ConstructiveReals}, CMorphisms.Proper + (CMorphisms.respectful (CReq R) (CMorphisms.respectful (CReq R) CRelationClasses.iffT)) (CRapart R). +Proof. + intros R x y H x0 y0 H0. destruct H, H0. split. + - intro. destruct H3. + left. apply (CRle_lt_trans _ x _ H). + apply (CRlt_le_trans _ x0 _ c), H2. + right. apply (CRle_lt_trans _ x0 _ H0). + apply (CRlt_le_trans _ x _ c), H1. + - intro. destruct H3. + left. apply (CRle_lt_trans _ y _ H1). + apply (CRlt_le_trans _ y0 _ c), H0. + right. apply (CRle_lt_trans _ y0 _ H2). + apply (CRlt_le_trans _ y _ c), H. +Qed. diff --git a/theories/Reals/Abstract/ConstructiveRealsMorphisms.v b/theories/Reals/Abstract/ConstructiveRealsMorphisms.v new file mode 100644 index 0000000000..bc44668e2f --- /dev/null +++ b/theories/Reals/Abstract/ConstructiveRealsMorphisms.v @@ -0,0 +1,1177 @@ +(************************************************************************) +(* * The Coq Proof Assistant / The Coq Development Team *) +(* v * INRIA, CNRS and contributors - Copyright 1999-2019 *) +(* <O___,, * (see CREDITS file for the list of authors) *) +(* \VV/ **************************************************************) +(* // * This file is distributed under the terms of the *) +(* * GNU Lesser General Public License Version 2.1 *) +(* * (see LICENSE file for the text of the license) *) +(************************************************************************) +(************************************************************************) + +(** Morphisms used to transport results from any instance of + ConstructiveReals to any other. + Between any two constructive reals structures R1 and R2, + all morphisms R1 -> R2 are extensionally equal. We will + further show that they exist, and so are isomorphisms. + The difference between two morphisms R1 -> R2 is therefore + the speed of computation. + + The canonical isomorphisms we provide here are often very slow, + when a new implementation of constructive reals is added, + it should define its own ad hoc isomorphisms for better speed. + + Apart from the speed, those unique isomorphisms also serve as + sanity checks of the interface ConstructiveReals : + it captures a concept with a strong notion of uniqueness. *) + +Require Import QArith. +Require Import Qabs. +Require Import ConstructiveReals. +Require Import ConstructiveLimits. +Require Import ConstructiveAbs. +Require Import ConstructiveSum. + +Local Open Scope ConstructiveReals. + +Record ConstructiveRealsMorphism {R1 R2 : ConstructiveReals} : Set := + { + CRmorph : CRcarrier R1 -> CRcarrier R2; + CRmorph_rat : forall q : Q, + CRmorph (CR_of_Q R1 q) == CR_of_Q R2 q; + CRmorph_increasing : forall x y : CRcarrier R1, + CRlt R1 x y -> CRlt R2 (CRmorph x) (CRmorph y); + }. + + +Lemma CRmorph_increasing_inv + : forall {R1 R2 : ConstructiveReals} + (f : ConstructiveRealsMorphism) + (x y : CRcarrier R1), + CRlt R2 (CRmorph f x) (CRmorph f y) + -> CRlt R1 x y. +Proof. + intros. destruct (CR_Q_dense R2 _ _ H) as [q [H0 H1]]. + destruct (CR_Q_dense R2 _ _ H0) as [r [H2 H3]]. + apply lt_CR_of_Q, (CR_of_Q_lt R1) in H3. + destruct (CRltLinear R1). + destruct (s _ x _ H3). + - exfalso. apply (CRmorph_increasing f) in c. + destruct (CRmorph_rat f r) as [H4 _]. + apply (CRle_lt_trans _ _ _ H4) in c. clear H4. + exact (CRlt_asym _ _ c H2). + - clear H2 H3 r. apply (CRlt_trans _ _ _ c). clear c. + destruct (CR_Q_dense R2 _ _ H1) as [t [H2 H3]]. + apply lt_CR_of_Q, (CR_of_Q_lt R1) in H2. + destruct (s _ y _ H2). exact c. + exfalso. apply (CRmorph_increasing f) in c. + destruct (CRmorph_rat f t) as [_ H4]. + apply (CRlt_le_trans _ _ _ c) in H4. clear c. + exact (CRlt_asym _ _ H4 H3). +Qed. + +Lemma CRmorph_unique : forall {R1 R2 : ConstructiveReals} + (f g : @ConstructiveRealsMorphism R1 R2) + (x : CRcarrier R1), + CRmorph f x == CRmorph g x. +Proof. + split. + - intro abs. destruct (CR_Q_dense R2 _ _ abs) as [q [H H0]]. + destruct (CRmorph_rat f q) as [H1 _]. + apply (CRlt_le_trans _ _ _ H) in H1. clear H. + apply CRmorph_increasing_inv in H1. + destruct (CRmorph_rat g q) as [_ H2]. + apply (CRle_lt_trans _ _ _ H2) in H0. clear H2. + apply CRmorph_increasing_inv in H0. + exact (CRlt_asym _ _ H0 H1). + - intro abs. destruct (CR_Q_dense R2 _ _ abs) as [q [H H0]]. + destruct (CRmorph_rat f q) as [_ H1]. + apply (CRle_lt_trans _ _ _ H1) in H0. clear H1. + apply CRmorph_increasing_inv in H0. + destruct (CRmorph_rat g q) as [H2 _]. + apply (CRlt_le_trans _ _ _ H) in H2. clear H. + apply CRmorph_increasing_inv in H2. + exact (CRlt_asym _ _ H0 H2). +Qed. + + +(* The identity is the only endomorphism of constructive reals. + For any ConstructiveReals R1, R2 and any morphisms + f : R1 -> R2 and g : R2 -> R1, + f and g are isomorphisms and are inverses of each other. *) +Lemma Endomorph_id + : forall {R : ConstructiveReals} (f : @ConstructiveRealsMorphism R R) + (x : CRcarrier R), + CRmorph f x == x. +Proof. + split. + - intro abs. destruct (CR_Q_dense R _ _ abs) as [q [H0 H1]]. + destruct (CRmorph_rat f q) as [H _]. + apply (CRlt_le_trans _ _ _ H0) in H. clear H0. + apply CRmorph_increasing_inv in H. + exact (CRlt_asym _ _ H1 H). + - intro abs. destruct (CR_Q_dense R _ _ abs) as [q [H0 H1]]. + destruct (CRmorph_rat f q) as [_ H]. + apply (CRle_lt_trans _ _ _ H) in H1. clear H. + apply CRmorph_increasing_inv in H1. + exact (CRlt_asym _ _ H1 H0). +Qed. + +Lemma CRmorph_proper + : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (x y : CRcarrier R1), + x == y -> CRmorph f x == CRmorph f y. +Proof. + split. + - intro abs. apply CRmorph_increasing_inv in abs. + destruct H. contradiction. + - intro abs. apply CRmorph_increasing_inv in abs. + destruct H. contradiction. +Qed. + +Definition CRmorph_compose {R1 R2 R3 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (g : @ConstructiveRealsMorphism R2 R3) + : @ConstructiveRealsMorphism R1 R3. +Proof. + apply (Build_ConstructiveRealsMorphism + R1 R3 (fun x:CRcarrier R1 => CRmorph g (CRmorph f x))). + - intro q. apply (CReq_trans _ (CRmorph g (CR_of_Q R2 q))). + apply CRmorph_proper. apply CRmorph_rat. apply CRmorph_rat. + - intros. apply CRmorph_increasing. apply CRmorph_increasing. exact H. +Defined. + +Lemma CRmorph_le : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (x y : CRcarrier R1), + x <= y -> CRmorph f x <= CRmorph f y. +Proof. + intros. intro abs. apply CRmorph_increasing_inv in abs. contradiction. +Qed. + +Lemma CRmorph_le_inv : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (x y : CRcarrier R1), + CRmorph f x <= CRmorph f y -> x <= y. +Proof. + intros. intro abs. apply (CRmorph_increasing f) in abs. contradiction. +Qed. + +Lemma CRmorph_zero : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2), + CRmorph f 0 == 0. +Proof. + intros. apply (CReq_trans _ (CRmorph f (CR_of_Q R1 0))). + apply CRmorph_proper. apply CReq_sym, CR_of_Q_zero. + apply (CReq_trans _ (CR_of_Q R2 0)). + apply CRmorph_rat. apply CR_of_Q_zero. +Qed. + +Lemma CRmorph_one : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2), + CRmorph f 1 == 1. +Proof. + intros. apply (CReq_trans _ (CRmorph f (CR_of_Q R1 1))). + apply CRmorph_proper. apply CReq_sym, CR_of_Q_one. + apply (CReq_trans _ (CR_of_Q R2 1)). + apply CRmorph_rat. apply CR_of_Q_one. +Qed. + +Lemma CRmorph_opp : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (x : CRcarrier R1), + CRmorph f (- x) == - CRmorph f x. +Proof. + split. + - intro abs. + destruct (CR_Q_dense R2 _ _ abs) as [q [H H0]]. clear abs. + destruct (CRmorph_rat f q) as [H1 _]. + apply (CRlt_le_trans _ _ _ H) in H1. clear H. + apply CRmorph_increasing_inv in H1. + apply CRopp_gt_lt_contravar in H0. + destruct (@CR_of_Q_opp R2 q) as [H2 _]. + apply (CRlt_le_trans _ _ _ H0) in H2. clear H0. + pose proof (CRopp_involutive (CRmorph f x)) as [H _]. + apply (CRle_lt_trans _ _ _ H) in H2. clear H. + destruct (CRmorph_rat f (-q)) as [H _]. + apply (CRlt_le_trans _ _ _ H2) in H. clear H2. + apply CRmorph_increasing_inv in H. + destruct (@CR_of_Q_opp R1 q) as [_ H2]. + apply (CRlt_le_trans _ _ _ H) in H2. clear H. + apply CRopp_gt_lt_contravar in H2. + pose proof (CRopp_involutive (CR_of_Q R1 q)) as [H _]. + apply (CRle_lt_trans _ _ _ H) in H2. clear H. + exact (CRlt_asym _ _ H1 H2). + - intro abs. + destruct (CR_Q_dense R2 _ _ abs) as [q [H H0]]. clear abs. + destruct (CRmorph_rat f q) as [_ H1]. + apply (CRle_lt_trans _ _ _ H1) in H0. clear H1. + apply CRmorph_increasing_inv in H0. + apply CRopp_gt_lt_contravar in H. + pose proof (CRopp_involutive (CRmorph f x)) as [_ H1]. + apply (CRlt_le_trans _ _ _ H) in H1. clear H. + destruct (@CR_of_Q_opp R2 q) as [_ H2]. + apply (CRle_lt_trans _ _ _ H2) in H1. clear H2. + destruct (CRmorph_rat f (-q)) as [_ H]. + apply (CRle_lt_trans _ _ _ H) in H1. clear H. + apply CRmorph_increasing_inv in H1. + destruct (@CR_of_Q_opp R1 q) as [H2 _]. + apply (CRle_lt_trans _ _ _ H2) in H1. clear H2. + apply CRopp_gt_lt_contravar in H1. + pose proof (CRopp_involutive (CR_of_Q R1 q)) as [_ H]. + apply (CRlt_le_trans _ _ _ H1) in H. clear H1. + exact (CRlt_asym _ _ H0 H). +Qed. + +Lemma CRplus_pos_rat_lt : forall {R : ConstructiveReals} (x : CRcarrier R) (q : Q), + Qlt 0 q -> CRlt R x (CRplus R x (CR_of_Q R q)). +Proof. + intros. + apply (CRle_lt_trans _ (CRplus R x (CRzero R))). apply CRplus_0_r. + apply CRplus_lt_compat_l. + apply (CRle_lt_trans _ (CR_of_Q R 0)). apply CR_of_Q_zero. + apply CR_of_Q_lt. exact H. +Defined. + +Lemma CRplus_neg_rat_lt : forall {R : ConstructiveReals} (x : CRcarrier R) (q : Q), + Qlt q 0 -> CRlt R (CRplus R x (CR_of_Q R q)) x. +Proof. + intros. + apply (CRlt_le_trans _ (CRplus R x (CRzero R))). 2: apply CRplus_0_r. + apply CRplus_lt_compat_l. + apply (CRlt_le_trans _ (CR_of_Q R 0)). + apply CR_of_Q_lt. exact H. apply CR_of_Q_zero. +Qed. + +Lemma CRmorph_plus_rat : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (x : CRcarrier R1) (q : Q), + CRmorph f (CRplus R1 x (CR_of_Q R1 q)) + == CRplus R2 (CRmorph f x) (CR_of_Q R2 q). +Proof. + split. + - intro abs. + destruct (CR_Q_dense R2 _ _ abs) as [r [H H0]]. clear abs. + destruct (CRmorph_rat f r) as [H1 _]. + apply (CRlt_le_trans _ _ _ H) in H1. clear H. + apply CRmorph_increasing_inv in H1. + apply (CRlt_asym _ _ H1). clear H1. + apply (CRplus_lt_reg_r (CRopp R1 (CR_of_Q R1 q))). + apply (CRlt_le_trans _ x). + apply (CRle_lt_trans _ (CR_of_Q R1 (r-q))). + apply (CRle_trans _ (CRplus R1 (CR_of_Q R1 r) (CR_of_Q R1 (-q)))). + apply CRplus_le_compat_l. destruct (@CR_of_Q_opp R1 q). exact H. + destruct (CR_of_Q_plus R1 r (-q)). exact H. + apply (CRmorph_increasing_inv f). + apply (CRle_lt_trans _ (CR_of_Q R2 (r - q))). + apply CRmorph_rat. + apply (CRplus_lt_reg_r (CR_of_Q R2 q)). + apply (CRle_lt_trans _ (CR_of_Q R2 r)). 2: exact H0. + intro H. + destruct (CR_of_Q_plus R2 (r-q) q) as [H1 _]. + apply (CRlt_le_trans _ _ _ H) in H1. clear H. + apply lt_CR_of_Q in H1. ring_simplify in H1. + exact (Qlt_not_le _ _ H1 (Qle_refl _)). + destruct (CRisRing R1). + apply (CRle_trans + _ (CRplus R1 x (CRplus R1 (CR_of_Q R1 q) (CRopp R1 (CR_of_Q R1 q))))). + apply (CRle_trans _ (CRplus R1 x (CRzero R1))). + destruct (CRplus_0_r x). exact H. + apply CRplus_le_compat_l. destruct (Ropp_def (CR_of_Q R1 q)). exact H. + destruct (Radd_assoc x (CR_of_Q R1 q) (CRopp R1 (CR_of_Q R1 q))). + exact H1. + - intro abs. + destruct (CR_Q_dense R2 _ _ abs) as [r [H H0]]. clear abs. + destruct (CRmorph_rat f r) as [_ H1]. + apply (CRle_lt_trans _ _ _ H1) in H0. clear H1. + apply CRmorph_increasing_inv in H0. + apply (CRlt_asym _ _ H0). clear H0. + apply (CRplus_lt_reg_r (CRopp R1 (CR_of_Q R1 q))). + apply (CRle_lt_trans _ x). + destruct (CRisRing R1). + apply (CRle_trans + _ (CRplus R1 x (CRplus R1 (CR_of_Q R1 q) (CRopp R1 (CR_of_Q R1 q))))). + destruct (Radd_assoc x (CR_of_Q R1 q) (CRopp R1 (CR_of_Q R1 q))). + exact H0. + apply (CRle_trans _ (CRplus R1 x (CRzero R1))). + apply CRplus_le_compat_l. destruct (Ropp_def (CR_of_Q R1 q)). exact H1. + destruct (CRplus_0_r x). exact H1. + apply (CRlt_le_trans _ (CR_of_Q R1 (r-q))). + apply (CRmorph_increasing_inv f). + apply (CRlt_le_trans _ (CR_of_Q R2 (r - q))). + apply (CRplus_lt_reg_r (CR_of_Q R2 q)). + apply (CRlt_le_trans _ _ _ H). + 2: apply CRmorph_rat. + apply (CRle_trans _ (CR_of_Q R2 (r-q+q))). + intro abs. apply lt_CR_of_Q in abs. ring_simplify in abs. + exact (Qlt_not_le _ _ abs (Qle_refl _)). + destruct (CR_of_Q_plus R2 (r-q) q). exact H1. + apply (CRle_trans _ (CRplus R1 (CR_of_Q R1 r) (CR_of_Q R1 (-q)))). + destruct (CR_of_Q_plus R1 r (-q)). exact H1. + apply CRplus_le_compat_l. destruct (@CR_of_Q_opp R1 q). exact H1. +Qed. + +Lemma CRmorph_plus : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (x y : CRcarrier R1), + CRmorph f (CRplus R1 x y) + == CRplus R2 (CRmorph f x) (CRmorph f y). +Proof. + intros R1 R2 f. + assert (forall (x y : CRcarrier R1), + CRplus R2 (CRmorph f x) (CRmorph f y) + <= CRmorph f (CRplus R1 x y)). + { intros x y abs. destruct (CR_Q_dense R2 _ _ abs) as [r [H H0]]. clear abs. + destruct (CRmorph_rat f r) as [H1 _]. + apply (CRlt_le_trans _ _ _ H) in H1. clear H. + apply CRmorph_increasing_inv in H1. + apply (CRlt_asym _ _ H1). clear H1. + destruct (CR_Q_dense R2 _ _ H0) as [q [H2 H3]]. + apply lt_CR_of_Q in H2. + assert (Qlt (r-q) 0) as epsNeg. + { apply (Qplus_lt_r _ _ q). ring_simplify. exact H2. } + destruct (CR_Q_dense R1 _ _ (CRplus_neg_rat_lt x (r-q) epsNeg)) + as [s [H4 H5]]. + apply (CRlt_trans _ (CRplus R1 (CR_of_Q R1 s) y)). + 2: apply CRplus_lt_compat_r, H5. + apply (CRmorph_increasing_inv f). + apply (CRlt_le_trans _ (CRplus R2 (CR_of_Q R2 s) (CRmorph f y))). + apply (CRmorph_increasing f) in H4. + destruct (CRmorph_plus_rat f x (r-q)) as [H _]. + apply (CRle_lt_trans _ _ _ H) in H4. clear H. + destruct (CRmorph_rat f s) as [_ H1]. + apply (CRlt_le_trans _ _ _ H4) in H1. clear H4. + apply (CRlt_trans + _ (CRplus R2 (CRplus R2 (CRmorph f x) (CR_of_Q R2 (r - q))) + (CRmorph f y))). + 2: apply CRplus_lt_compat_r, H1. + apply (CRlt_le_trans + _ (CRplus R2 (CRplus R2 (CR_of_Q R2 (r - q)) (CRmorph f x)) + (CRmorph f y))). + apply (CRlt_le_trans + _ (CRplus R2 (CR_of_Q R2 (r - q)) + (CRplus R2 (CRmorph f x) (CRmorph f y)))). + apply (CRle_lt_trans _ (CRplus R2 (CR_of_Q R2 (r - q)) (CR_of_Q R2 q))). + 2: apply CRplus_lt_compat_l, H3. + intro abs. + destruct (CR_of_Q_plus R2 (r-q) q) as [_ H4]. + apply (CRle_lt_trans _ _ _ H4) in abs. clear H4. + destruct (CRmorph_rat f r) as [_ H4]. + apply (CRlt_le_trans _ _ _ abs) in H4. clear abs. + apply lt_CR_of_Q in H4. ring_simplify in H4. + exact (Qlt_not_le _ _ H4 (Qle_refl _)). + destruct (CRisRing R2); apply Radd_assoc. + apply CRplus_le_compat_r. destruct (CRisRing R2). + destruct (Radd_comm (CRmorph f x) (CR_of_Q R2 (r - q))). + exact H. + intro abs. + destruct (CRmorph_plus_rat f y s) as [H _]. apply H. clear H. + apply (CRlt_le_trans _ (CRplus R2 (CR_of_Q R2 s) (CRmorph f y))). + apply (CRle_lt_trans _ (CRmorph f (CRplus R1 (CR_of_Q R1 s) y))). + apply CRmorph_proper. destruct (CRisRing R1); apply Radd_comm. + exact abs. destruct (CRisRing R2); apply Radd_comm. } + split. + - apply H. + - specialize (H (CRplus R1 x y) (CRopp R1 y)). + intro abs. apply H. clear H. + apply (CRle_lt_trans _ (CRmorph f x)). + apply CRmorph_proper. destruct (CRisRing R1). + apply (CReq_trans _ (CRplus R1 x (CRplus R1 y (CRopp R1 y)))). + apply CReq_sym, Radd_assoc. + apply (CReq_trans _ (CRplus R1 x (CRzero R1))). 2: apply CRplus_0_r. + destruct (CRisRingExt R1). apply Radd_ext. + apply CReq_refl. apply Ropp_def. + apply (CRplus_lt_reg_r (CRmorph f y)). + apply (CRlt_le_trans _ _ _ abs). clear abs. + apply (CRle_trans _ (CRplus R2 (CRmorph f (CRplus R1 x y)) (CRzero R2))). + destruct (CRplus_0_r (CRmorph f (CRplus R1 x y))). exact H. + apply (CRle_trans _ (CRplus R2 (CRmorph f (CRplus R1 x y)) + (CRplus R2 (CRmorph f (CRopp R1 y)) (CRmorph f y)))). + apply CRplus_le_compat_l. + apply (CRle_trans + _ (CRplus R2 (CRopp R2 (CRmorph f y)) (CRmorph f y))). + destruct (CRplus_opp_l (CRmorph f y)). exact H. + apply CRplus_le_compat_r. destruct (CRmorph_opp f y). exact H. + destruct (CRisRing R2). + destruct (Radd_assoc (CRmorph f (CRplus R1 x y)) + (CRmorph f (CRopp R1 y)) (CRmorph f y)). + exact H0. +Qed. + +Lemma CRmorph_mult_pos : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (x : CRcarrier R1) (n : nat), + CRmorph f (CRmult R1 x (CR_of_Q R1 (Z.of_nat n # 1))) + == CRmult R2 (CRmorph f x) (CR_of_Q R2 (Z.of_nat n # 1)). +Proof. + induction n. + - simpl. destruct (CRisRingExt R1). + apply (CReq_trans _ (CRzero R2)). + + apply (CReq_trans _ (CRmorph f (CRzero R1))). + 2: apply CRmorph_zero. apply CRmorph_proper. + apply (CReq_trans _ (CRmult R1 x (CRzero R1))). + 2: apply CRmult_0_r. apply Rmul_ext. apply CReq_refl. apply CR_of_Q_zero. + + apply (CReq_trans _ (CRmult R2 (CRmorph f x) (CRzero R2))). + apply CReq_sym, CRmult_0_r. destruct (CRisRingExt R2). + apply Rmul_ext0. apply CReq_refl. apply CReq_sym, CR_of_Q_zero. + - destruct (CRisRingExt R1), (CRisRingExt R2). + apply (CReq_trans + _ (CRmorph f (CRplus R1 x (CRmult R1 x (CR_of_Q R1 (Z.of_nat n # 1)))))). + apply CRmorph_proper. + apply (CReq_trans + _ (CRmult R1 x (CRplus R1 (CRone R1) (CR_of_Q R1 (Z.of_nat n # 1))))). + apply Rmul_ext. apply CReq_refl. + apply (CReq_trans _ (CR_of_Q R1 (1 + (Z.of_nat n # 1)))). + apply CR_of_Q_morph. rewrite Nat2Z.inj_succ. unfold Z.succ. + rewrite Z.add_comm. rewrite Qinv_plus_distr. reflexivity. + apply (CReq_trans _ (CRplus R1 (CR_of_Q R1 1) (CR_of_Q R1 (Z.of_nat n # 1)))). + apply CR_of_Q_plus. apply Radd_ext. apply CR_of_Q_one. apply CReq_refl. + apply (CReq_trans _ (CRplus R1 (CRmult R1 x (CRone R1)) + (CRmult R1 x (CR_of_Q R1 (Z.of_nat n # 1))))). + apply CRmult_plus_distr_l. apply Radd_ext. apply CRmult_1_r. apply CReq_refl. + apply (CReq_trans + _ (CRplus R2 (CRmorph f x) + (CRmorph f (CRmult R1 x (CR_of_Q R1 (Z.of_nat n # 1)))))). + apply CRmorph_plus. + apply (CReq_trans + _ (CRplus R2 (CRmorph f x) + (CRmult R2 (CRmorph f x) (CR_of_Q R2 (Z.of_nat n # 1))))). + apply Radd_ext0. apply CReq_refl. exact IHn. + apply (CReq_trans + _ (CRmult R2 (CRmorph f x) (CRplus R2 (CRone R2) (CR_of_Q R2 (Z.of_nat n # 1))))). + apply (CReq_trans + _ (CRplus R2 (CRmult R2 (CRmorph f x) (CRone R2)) + (CRmult R2 (CRmorph f x) (CR_of_Q R2 (Z.of_nat n # 1))))). + apply Radd_ext0. 2: apply CReq_refl. apply CReq_sym, CRmult_1_r. + apply CReq_sym, CRmult_plus_distr_l. + apply Rmul_ext0. apply CReq_refl. + apply (CReq_trans _ (CR_of_Q R2 (1 + (Z.of_nat n # 1)))). + apply (CReq_trans _ (CRplus R2 (CR_of_Q R2 1) (CR_of_Q R2 (Z.of_nat n # 1)))). + apply Radd_ext0. apply CReq_sym, CR_of_Q_one. apply CReq_refl. + apply CReq_sym, CR_of_Q_plus. + apply CR_of_Q_morph. rewrite Nat2Z.inj_succ. unfold Z.succ. + rewrite Z.add_comm. rewrite Qinv_plus_distr. reflexivity. +Qed. + +Lemma NatOfZ : forall n : Z, { p : nat | n = Z.of_nat p \/ n = Z.opp (Z.of_nat p) }. +Proof. + intros [|p|n]. + - exists O. left. reflexivity. + - exists (Pos.to_nat p). left. rewrite positive_nat_Z. reflexivity. + - exists (Pos.to_nat n). right. rewrite positive_nat_Z. reflexivity. +Qed. + +Lemma CRmorph_mult_int : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (x : CRcarrier R1) (n : Z), + CRmorph f (CRmult R1 x (CR_of_Q R1 (n # 1))) + == CRmult R2 (CRmorph f x) (CR_of_Q R2 (n # 1)). +Proof. + intros. destruct (NatOfZ n) as [p [pos|neg]]. + - subst n. apply CRmorph_mult_pos. + - subst n. + apply (CReq_trans + _ (CRopp R2 (CRmorph f (CRmult R1 x (CR_of_Q R1 (Z.of_nat p # 1)))))). + + apply (CReq_trans + _ (CRmorph f (CRopp R1 (CRmult R1 x (CR_of_Q R1 (Z.of_nat p # 1)))))). + 2: apply CRmorph_opp. apply CRmorph_proper. + apply (CReq_trans _ (CRmult R1 x (CR_of_Q R1 (- (Z.of_nat p # 1))))). + destruct (CRisRingExt R1). apply Rmul_ext. apply CReq_refl. + apply CR_of_Q_morph. reflexivity. + apply (CReq_trans _ (CRmult R1 x (CRopp R1 (CR_of_Q R1 (Z.of_nat p # 1))))). + destruct (CRisRingExt R1). apply Rmul_ext. apply CReq_refl. + apply CR_of_Q_opp. apply CReq_sym, CRopp_mult_distr_r. + + apply (CReq_trans + _ (CRopp R2 (CRmult R2 (CRmorph f x) (CR_of_Q R2 (Z.of_nat p # 1))))). + destruct (CRisRingExt R2). apply Ropp_ext. apply CRmorph_mult_pos. + apply (CReq_trans + _ (CRmult R2 (CRmorph f x) (CRopp R2 (CR_of_Q R2 (Z.of_nat p # 1))))). + apply CRopp_mult_distr_r. destruct (CRisRingExt R2). + apply Rmul_ext. apply CReq_refl. + apply (CReq_trans _ (CR_of_Q R2 (- (Z.of_nat p # 1)))). + apply CReq_sym, CR_of_Q_opp. apply CR_of_Q_morph. reflexivity. +Qed. + +Lemma CRmorph_mult_inv : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (x : CRcarrier R1) (p : positive), + CRmorph f (CRmult R1 x (CR_of_Q R1 (1 # p))) + == CRmult R2 (CRmorph f x) (CR_of_Q R2 (1 # p)). +Proof. + intros. apply (CRmult_eq_reg_r (CR_of_Q R2 (Z.pos p # 1))). + left. apply (CRle_lt_trans _ (CR_of_Q R2 0)). + apply CR_of_Q_zero. apply CR_of_Q_lt. reflexivity. + apply (CReq_trans _ (CRmorph f x)). + - apply (CReq_trans + _ (CRmorph f (CRmult R1 (CRmult R1 x (CR_of_Q R1 (1 # p))) + (CR_of_Q R1 (Z.pos p # 1))))). + apply CReq_sym, CRmorph_mult_int. apply CRmorph_proper. + apply (CReq_trans + _ (CRmult R1 x (CRmult R1 (CR_of_Q R1 (1 # p)) + (CR_of_Q R1 (Z.pos p # 1))))). + destruct (CRisRing R1). apply CReq_sym, Rmul_assoc. + apply (CReq_trans _ (CRmult R1 x (CRone R1))). + apply (Rmul_ext (CRisRingExt R1)). apply CReq_refl. + apply (CReq_trans _ (CR_of_Q R1 ((1#p) * (Z.pos p # 1)))). + apply CReq_sym, CR_of_Q_mult. + apply (CReq_trans _ (CR_of_Q R1 1)). + apply CR_of_Q_morph. reflexivity. apply CR_of_Q_one. + apply CRmult_1_r. + - apply (CReq_trans + _ (CRmult R2 (CRmorph f x) + (CRmult R2 (CR_of_Q R2 (1 # p)) (CR_of_Q R2 (Z.pos p # 1))))). + 2: apply (Rmul_assoc (CRisRing R2)). + apply (CReq_trans _ (CRmult R2 (CRmorph f x) (CRone R2))). + apply CReq_sym, CRmult_1_r. + apply (Rmul_ext (CRisRingExt R2)). apply CReq_refl. + apply (CReq_trans _ (CR_of_Q R2 1)). + apply CReq_sym, CR_of_Q_one. + apply (CReq_trans _ (CR_of_Q R2 ((1#p)*(Z.pos p # 1)))). + apply CR_of_Q_morph. reflexivity. apply CR_of_Q_mult. +Qed. + +Lemma CRmorph_mult_rat : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (x : CRcarrier R1) (q : Q), + CRmorph f (CRmult R1 x (CR_of_Q R1 q)) + == CRmult R2 (CRmorph f x) (CR_of_Q R2 q). +Proof. + intros. destruct q as [a b]. + apply (CReq_trans + _ (CRmult R2 (CRmorph f (CRmult R1 x (CR_of_Q R1 (a # 1)))) + (CR_of_Q R2 (1 # b)))). + - apply (CReq_trans + _ (CRmorph f (CRmult R1 (CRmult R1 x (CR_of_Q R1 (a # 1))) + (CR_of_Q R1 (1 # b))))). + 2: apply CRmorph_mult_inv. apply CRmorph_proper. + apply (CReq_trans + _ (CRmult R1 x (CRmult R1 (CR_of_Q R1 (a # 1)) + (CR_of_Q R1 (1 # b))))). + apply (Rmul_ext (CRisRingExt R1)). apply CReq_refl. + apply (CReq_trans _ (CR_of_Q R1 ((a#1)*(1#b)))). + apply CR_of_Q_morph. unfold Qeq; simpl. rewrite Z.mul_1_r. reflexivity. + apply CR_of_Q_mult. + apply (Rmul_assoc (CRisRing R1)). + - apply (CReq_trans + _ (CRmult R2 (CRmult R2 (CRmorph f x) (CR_of_Q R2 (a # 1))) + (CR_of_Q R2 (1 # b)))). + apply (Rmul_ext (CRisRingExt R2)). apply CRmorph_mult_int. + apply CReq_refl. + apply (CReq_trans + _ (CRmult R2 (CRmorph f x) + (CRmult R2 (CR_of_Q R2 (a # 1)) (CR_of_Q R2 (1 # b))))). + apply CReq_sym, (Rmul_assoc (CRisRing R2)). + apply (Rmul_ext (CRisRingExt R2)). apply CReq_refl. + apply (CReq_trans _ (CR_of_Q R2 ((a#1)*(1#b)))). + apply CReq_sym, CR_of_Q_mult. + apply CR_of_Q_morph. unfold Qeq; simpl. rewrite Z.mul_1_r. reflexivity. +Qed. + +Lemma CRmorph_mult_pos_pos_le : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (x y : CRcarrier R1), + CRlt R1 (CRzero R1) y + -> CRmult R2 (CRmorph f x) (CRmorph f y) + <= CRmorph f (CRmult R1 x y). +Proof. + intros. intro abs. destruct (CR_Q_dense R2 _ _ abs) as [q [H1 H2]]. + destruct (CRmorph_rat f q) as [H3 _]. + apply (CRlt_le_trans _ _ _ H1) in H3. clear H1. + apply CRmorph_increasing_inv in H3. + apply (CRlt_asym _ _ H3). clear H3. + destruct (CR_Q_dense R2 _ _ H2) as [r [H1 H3]]. + apply lt_CR_of_Q in H1. + destruct (CR_archimedean R1 y) as [A Amaj]. + assert (/ ((r - q) * (1 # A)) * (q - r) == - (Z.pos A # 1))%Q as diveq. + { rewrite Qinv_mult_distr. setoid_replace (q-r)%Q with (-1*(r-q))%Q. + field_simplify. reflexivity. 2: field. + split. intro H4. inversion H4. intro H4. + apply Qlt_minus_iff in H1. rewrite H4 in H1. inversion H1. } + destruct (CR_Q_dense R1 (CRplus R1 x (CR_of_Q R1 ((q-r) * (1#A)))) x) + as [s [H4 H5]]. + - apply (CRlt_le_trans _ (CRplus R1 x (CRzero R1))). + 2: apply CRplus_0_r. apply CRplus_lt_compat_l. + apply (CRplus_lt_reg_l R1 (CR_of_Q R1 ((r-q) * (1#A)))). + apply (CRle_lt_trans _ (CRzero R1)). + apply (CRle_trans _ (CR_of_Q R1 ((r-q)*(1#A) + (q-r)*(1#A)))). + destruct (CR_of_Q_plus R1 ((r-q)*(1#A)) ((q-r)*(1#A))). + exact H0. apply (CRle_trans _ (CR_of_Q R1 0)). + 2: destruct (@CR_of_Q_zero R1); exact H4. + intro H4. apply lt_CR_of_Q in H4. ring_simplify in H4. + inversion H4. + apply (CRlt_le_trans _ (CR_of_Q R1 ((r - q) * (1 # A)))). + 2: apply CRplus_0_r. + apply (CRle_lt_trans _ (CR_of_Q R1 0)). + apply CR_of_Q_zero. apply CR_of_Q_lt. + rewrite <- (Qmult_0_r (r-q)). apply Qmult_lt_l. + apply Qlt_minus_iff in H1. exact H1. reflexivity. + - apply (CRmorph_increasing f) in H4. + destruct (CRmorph_plus f x (CR_of_Q R1 ((q-r) * (1#A)))) as [H6 _]. + apply (CRle_lt_trans _ _ _ H6) in H4. clear H6. + destruct (CRmorph_rat f s) as [_ H6]. + apply (CRlt_le_trans _ _ _ H4) in H6. clear H4. + apply (CRmult_lt_compat_r (CRmorph f y)) in H6. + destruct (Rdistr_l (CRisRing R2) (CRmorph f x) + (CRmorph f (CR_of_Q R1 ((q-r) * (1#A)))) + (CRmorph f y)) as [H4 _]. + apply (CRle_lt_trans _ _ _ H4) in H6. clear H4. + apply (CRle_lt_trans _ (CRmult R1 (CR_of_Q R1 s) y)). + 2: apply CRmult_lt_compat_r. 2: exact H. 2: exact H5. + apply (CRmorph_le_inv f). + apply (CRle_trans _ (CR_of_Q R2 q)). + destruct (CRmorph_rat f q). exact H4. + apply (CRle_trans _ (CRmult R2 (CR_of_Q R2 s) (CRmorph f y))). + apply (CRle_trans _ (CRplus R2 (CRmult R2 (CRmorph f x) (CRmorph f y)) + (CR_of_Q R2 (q-r)))). + apply (CRle_trans _ (CRplus R2 (CR_of_Q R2 r) (CR_of_Q R2 (q - r)))). + + apply (CRle_trans _ (CR_of_Q R2 (r + (q-r)))). + intro H4. apply lt_CR_of_Q in H4. ring_simplify in H4. + exact (Qlt_not_le q q H4 (Qle_refl q)). + destruct (CR_of_Q_plus R2 r (q-r)). exact H4. + + apply CRplus_le_compat_r. intro H4. + apply (CRlt_asym _ _ H3). exact H4. + + intro H4. apply (CRlt_asym _ _ H4). clear H4. + apply (CRlt_trans_flip _ _ _ H6). clear H6. + apply CRplus_lt_compat_l. + apply (CRlt_le_trans + _ (CRmult R2 (CR_of_Q R2 ((q - r) * (1 # A))) (CRmorph f y))). + apply (CRmult_lt_reg_l (CR_of_Q R2 (/((r-q)*(1#A))))). + apply (CRle_lt_trans _ (CR_of_Q R2 0)). apply CR_of_Q_zero. + apply CR_of_Q_lt, Qinv_lt_0_compat. + rewrite <- (Qmult_0_r (r-q)). apply Qmult_lt_l. + apply Qlt_minus_iff in H1. exact H1. reflexivity. + apply (CRle_lt_trans _ (CRopp R2 (CR_of_Q R2 (Z.pos A # 1)))). + apply (CRle_trans _ (CR_of_Q R2 (-(Z.pos A # 1)))). + apply (CRle_trans _ (CR_of_Q R2 ((/ ((r - q) * (1 # A))) * (q - r)))). + destruct (CR_of_Q_mult R2 (/ ((r - q) * (1 # A))) (q - r)). + exact H0. destruct (CR_of_Q_morph R2 (/ ((r - q) * (1 # A)) * (q - r)) + (-(Z.pos A # 1))). + exact diveq. intro H7. apply lt_CR_of_Q in H7. + rewrite diveq in H7. exact (Qlt_not_le _ _ H7 (Qle_refl _)). + destruct (@CR_of_Q_opp R2 (Z.pos A # 1)). exact H4. + apply (CRlt_le_trans _ (CRopp R2 (CRmorph f y))). + apply CRopp_gt_lt_contravar. + apply (CRlt_le_trans _ (CRmorph f (CR_of_Q R1 (Z.pos A # 1)))). + apply CRmorph_increasing. exact Amaj. + destruct (CRmorph_rat f (Z.pos A # 1)). exact H4. + apply (CRle_trans _ (CRmult R2 (CRopp R2 (CRone R2)) (CRmorph f y))). + apply (CRle_trans _ (CRopp R2 (CRmult R2 (CRone R2) (CRmorph f y)))). + destruct (Ropp_ext (CRisRingExt R2) (CRmorph f y) + (CRmult R2 (CRone R2) (CRmorph f y))). + apply CReq_sym, (Rmul_1_l (CRisRing R2)). exact H4. + destruct (CRopp_mult_distr_l (CRone R2) (CRmorph f y)). exact H4. + apply (CRle_trans _ (CRmult R2 (CRmult R2 (CR_of_Q R2 (/ ((r - q) * (1 # A)))) + (CR_of_Q R2 ((q - r) * (1 # A)))) + (CRmorph f y))). + apply CRmult_le_compat_r_half. + apply (CRle_lt_trans _ (CRmorph f (CRzero R1))). + apply CRmorph_zero. apply CRmorph_increasing. exact H. + apply (CRle_trans _ (CR_of_Q R2 ((/ ((r - q) * (1 # A))) + * ((q - r) * (1 # A))))). + apply (CRle_trans _ (CR_of_Q R2 (-1))). + apply (CRle_trans _ (CRopp R2 (CR_of_Q R2 1))). + destruct (Ropp_ext (CRisRingExt R2) (CRone R2) (CR_of_Q R2 1)). + apply CReq_sym, CR_of_Q_one. exact H4. + destruct (@CR_of_Q_opp R2 1). exact H0. + destruct (CR_of_Q_morph R2 (-1) (/ ((r - q) * (1 # A)) * ((q - r) * (1 # A)))). + field. split. + intro H4. inversion H4. intro H4. apply Qlt_minus_iff in H1. + rewrite H4 in H1. inversion H1. exact H4. + destruct (CR_of_Q_mult R2 (/ ((r - q) * (1 # A))) ((q - r) * (1 # A))). + exact H4. + destruct (Rmul_assoc (CRisRing R2) (CR_of_Q R2 (/ ((r - q) * (1 # A)))) + (CR_of_Q R2 ((q - r) * (1 # A))) + (CRmorph f y)). + exact H0. + apply CRmult_le_compat_r_half. + apply (CRle_lt_trans _ (CRmorph f (CRzero R1))). + apply CRmorph_zero. apply CRmorph_increasing. exact H. + destruct (CRmorph_rat f ((q - r) * (1 # A))). exact H0. + + apply (CRle_trans _ (CRmorph f (CRmult R1 y (CR_of_Q R1 s)))). + apply (CRle_trans _ (CRmult R2 (CRmorph f y) (CR_of_Q R2 s))). + destruct (Rmul_comm (CRisRing R2) (CRmorph f y) (CR_of_Q R2 s)). + exact H0. + destruct (CRmorph_mult_rat f y s). exact H0. + destruct (CRmorph_proper f (CRmult R1 y (CR_of_Q R1 s)) + (CRmult R1 (CR_of_Q R1 s) y)). + apply (Rmul_comm (CRisRing R1)). exact H4. + + apply (CRle_lt_trans _ (CRmorph f (CRzero R1))). + apply CRmorph_zero. apply CRmorph_increasing. exact H. +Qed. + +Lemma CRmorph_mult_pos_pos : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (x y : CRcarrier R1), + CRlt R1 (CRzero R1) y + -> CRmorph f (CRmult R1 x y) + == CRmult R2 (CRmorph f x) (CRmorph f y). +Proof. + split. apply CRmorph_mult_pos_pos_le. exact H. + intro abs. destruct (CR_Q_dense R2 _ _ abs) as [q [H1 H2]]. + destruct (CRmorph_rat f q) as [_ H3]. + apply (CRle_lt_trans _ _ _ H3) in H2. clear H3. + apply CRmorph_increasing_inv in H2. + apply (CRlt_asym _ _ H2). clear H2. + destruct (CR_Q_dense R2 _ _ H1) as [r [H2 H3]]. + apply lt_CR_of_Q in H3. + destruct (CR_archimedean R1 y) as [A Amaj]. + destruct (CR_Q_dense R1 x (CRplus R1 x (CR_of_Q R1 ((q-r) * (1#A))))) + as [s [H4 H5]]. + - apply (CRle_lt_trans _ (CRplus R1 x (CRzero R1))). + apply CRplus_0_r. apply CRplus_lt_compat_l. + apply (CRle_lt_trans _ (CR_of_Q R1 0)). + apply CR_of_Q_zero. apply CR_of_Q_lt. + rewrite <- (Qmult_0_r (q-r)). apply Qmult_lt_l. + apply Qlt_minus_iff in H3. exact H3. reflexivity. + - apply (CRmorph_increasing f) in H5. + destruct (CRmorph_plus f x (CR_of_Q R1 ((q-r) * (1#A)))) as [_ H6]. + apply (CRlt_le_trans _ _ _ H5) in H6. clear H5. + destruct (CRmorph_rat f s) as [H5 _ ]. + apply (CRle_lt_trans _ _ _ H5) in H6. clear H5. + apply (CRmult_lt_compat_r (CRmorph f y)) in H6. + apply (CRlt_le_trans _ (CRmult R1 (CR_of_Q R1 s) y)). + apply CRmult_lt_compat_r. exact H. exact H4. clear H4. + apply (CRmorph_le_inv f). + apply (CRle_trans _ (CR_of_Q R2 q)). + 2: destruct (CRmorph_rat f q); exact H0. + apply (CRle_trans _ (CRmult R2 (CR_of_Q R2 s) (CRmorph f y))). + + apply (CRle_trans _ (CRmorph f (CRmult R1 y (CR_of_Q R1 s)))). + destruct (CRmorph_proper f (CRmult R1 (CR_of_Q R1 s) y) + (CRmult R1 y (CR_of_Q R1 s))). + apply (Rmul_comm (CRisRing R1)). exact H4. + apply (CRle_trans _ (CRmult R2 (CRmorph f y) (CR_of_Q R2 s))). + exact (proj2 (CRmorph_mult_rat f y s)). + destruct (Rmul_comm (CRisRing R2) (CR_of_Q R2 s) (CRmorph f y)). + exact H0. + + intro H5. apply (CRlt_asym _ _ H5). clear H5. + apply (CRlt_trans _ _ _ H6). clear H6. + apply (CRle_lt_trans + _ (CRplus R2 + (CRmult R2 (CRmorph f x) (CRmorph f y)) + (CRmult R2 (CRmorph f (CR_of_Q R1 ((q - r) * (1 # A)))) + (CRmorph f y)))). + apply (Rdistr_l (CRisRing R2)). + apply (CRle_lt_trans + _ (CRplus R2 (CR_of_Q R2 r) + (CRmult R2 (CRmorph f (CR_of_Q R1 ((q - r) * (1 # A)))) + (CRmorph f y)))). + apply CRplus_le_compat_r. intro H5. apply (CRlt_asym _ _ H5 H2). + clear H2. + apply (CRle_lt_trans + _ (CRplus R2 (CR_of_Q R2 r) + (CRmult R2 (CR_of_Q R2 ((q - r) * (1 # A))) + (CRmorph f y)))). + apply CRplus_le_compat_l, CRmult_le_compat_r_half. + apply (CRle_lt_trans _ (CRmorph f (CRzero R1))). + apply CRmorph_zero. apply CRmorph_increasing. exact H. + destruct (CRmorph_rat f ((q - r) * (1 # A))). exact H2. + apply (CRlt_le_trans _ (CRplus R2 (CR_of_Q R2 r) + (CR_of_Q R2 ((q - r))))). + apply CRplus_lt_compat_l. + * apply (CRmult_lt_reg_l (CR_of_Q R2 (/((q - r) * (1 # A))))). + apply (CRle_lt_trans _ (CR_of_Q R2 0)). apply CR_of_Q_zero. + apply CR_of_Q_lt, Qinv_lt_0_compat. + rewrite <- (Qmult_0_r (q-r)). apply Qmult_lt_l. + apply Qlt_minus_iff in H3. exact H3. reflexivity. + apply (CRle_lt_trans _ (CRmorph f y)). + apply (CRle_trans _ (CRmult R2 (CRmult R2 (CR_of_Q R2 (/ ((q - r) * (1 # A)))) + (CR_of_Q R2 ((q - r) * (1 # A)))) + (CRmorph f y))). + exact (proj2 (Rmul_assoc (CRisRing R2) (CR_of_Q R2 (/ ((q - r) * (1 # A)))) + (CR_of_Q R2 ((q - r) * (1 # A))) + (CRmorph f y))). + apply (CRle_trans _ (CRmult R2 (CRone R2) (CRmorph f y))). + apply CRmult_le_compat_r_half. + apply (CRle_lt_trans _ (CRmorph f (CRzero R1))). + apply CRmorph_zero. apply CRmorph_increasing. exact H. + apply (CRle_trans + _ (CR_of_Q R2 ((/ ((q - r) * (1 # A))) * ((q - r) * (1 # A))))). + exact (proj1 (CR_of_Q_mult R2 (/ ((q - r) * (1 # A))) ((q - r) * (1 # A)))). + apply (CRle_trans _ (CR_of_Q R2 1)). + destruct (CR_of_Q_morph R2 (/ ((q - r) * (1 # A)) * ((q - r) * (1 # A))) 1). + field_simplify. reflexivity. split. + intro H5. inversion H5. intro H5. apply Qlt_minus_iff in H3. + rewrite H5 in H3. inversion H3. exact H2. + destruct (CR_of_Q_one R2). exact H2. + destruct (Rmul_1_l (CRisRing R2) (CRmorph f y)). + intro H5. contradiction. + apply (CRlt_le_trans _ (CR_of_Q R2 (Z.pos A # 1))). + apply (CRlt_le_trans _ (CRmorph f (CR_of_Q R1 (Z.pos A # 1)))). + apply CRmorph_increasing. exact Amaj. + exact (proj2 (CRmorph_rat f (Z.pos A # 1))). + apply (CRle_trans _ (CR_of_Q R2 ((/ ((q - r) * (1 # A))) * (q - r)))). + 2: exact (proj2 (CR_of_Q_mult R2 (/ ((q - r) * (1 # A))) (q - r))). + destruct (CR_of_Q_morph R2 (Z.pos A # 1) (/ ((q - r) * (1 # A)) * (q - r))). + field_simplify. reflexivity. split. + intro H5. inversion H5. intro H5. apply Qlt_minus_iff in H3. + rewrite H5 in H3. inversion H3. exact H2. + * apply (CRle_trans _ (CR_of_Q R2 (r + (q-r)))). + exact (proj1 (CR_of_Q_plus R2 r (q-r))). + destruct (CR_of_Q_morph R2 (r + (q-r)) q). ring. exact H2. + + apply (CRle_lt_trans _ (CRmorph f (CRzero R1))). + apply CRmorph_zero. apply CRmorph_increasing. exact H. +Qed. + +Lemma CRmorph_mult : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (x y : CRcarrier R1), + CRmorph f (CRmult R1 x y) + == CRmult R2 (CRmorph f x) (CRmorph f y). +Proof. + intros. + destruct (CR_archimedean R1 (CRopp R1 y)) as [p pmaj]. + apply (CRplus_eq_reg_r (CRmult R2 (CRmorph f x) + (CR_of_Q R2 (Z.pos p # 1)))). + apply (CReq_trans _ (CRmorph f (CRmult R1 x (CRplus R1 y (CR_of_Q R1 (Z.pos p # 1)))))). + - apply (CReq_trans _ (CRplus R2 (CRmorph f (CRmult R1 x y)) + (CRmorph f (CRmult R1 x (CR_of_Q R1 (Z.pos p # 1)))))). + apply (Radd_ext (CRisRingExt R2)). apply CReq_refl. + apply CReq_sym, CRmorph_mult_int. + apply (CReq_trans _ (CRmorph f (CRplus R1 (CRmult R1 x y) + (CRmult R1 x (CR_of_Q R1 (Z.pos p # 1)))))). + apply CReq_sym, CRmorph_plus. apply CRmorph_proper. + apply CReq_sym, CRmult_plus_distr_l. + - apply (CReq_trans _ (CRmult R2 (CRmorph f x) + (CRmorph f (CRplus R1 y (CR_of_Q R1 (Z.pos p # 1)))))). + apply CRmorph_mult_pos_pos. + apply (CRplus_lt_compat_l R1 y) in pmaj. + apply (CRle_lt_trans _ (CRplus R1 y (CRopp R1 y))). + 2: exact pmaj. apply (CRisRing R1). + apply (CReq_trans _ (CRmult R2 (CRmorph f x) + (CRplus R2 (CRmorph f y) (CR_of_Q R2 (Z.pos p # 1))))). + apply (Rmul_ext (CRisRingExt R2)). apply CReq_refl. + apply (CReq_trans _ (CRplus R2 (CRmorph f y) + (CRmorph f (CR_of_Q R1 (Z.pos p # 1))))). + apply CRmorph_plus. + apply (Radd_ext (CRisRingExt R2)). apply CReq_refl. + apply CRmorph_rat. + apply CRmult_plus_distr_l. +Qed. + +Lemma CRmorph_appart : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (x y : CRcarrier R1) + (app : x ≶ y), + CRmorph f x ≶ CRmorph f y. +Proof. + intros. destruct app. + - left. apply CRmorph_increasing. exact c. + - right. apply CRmorph_increasing. exact c. +Defined. + +Lemma CRmorph_appart_zero : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (x : CRcarrier R1) + (app : x ≶ 0), + CRmorph f x ≶ 0. +Proof. + intros. destruct app. + - left. apply (CRlt_le_trans _ (CRmorph f (CRzero R1))). + apply CRmorph_increasing. exact c. + exact (proj2 (CRmorph_zero f)). + - right. apply (CRle_lt_trans _ (CRmorph f (CRzero R1))). + exact (proj1 (CRmorph_zero f)). + apply CRmorph_increasing. exact c. +Defined. + +Lemma CRmorph_inv : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (x : CRcarrier R1) + (xnz : x ≶ 0) + (fxnz : CRmorph f x ≶ 0), + CRmorph f ((/ x) xnz) + == (/ CRmorph f x) fxnz. +Proof. + intros. apply (CRmult_eq_reg_r (CRmorph f x)). + destruct fxnz. right. exact c. left. exact c. + apply (CReq_trans _ (CRone R2)). + 2: apply CReq_sym, CRinv_l. + apply (CReq_trans _ (CRmorph f (CRmult R1 ((/ x) xnz) x))). + apply CReq_sym, CRmorph_mult. + apply (CReq_trans _ (CRmorph f 1)). + apply CRmorph_proper. apply CRinv_l. + apply CRmorph_one. +Qed. + +Lemma CRmorph_sum : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (un : nat -> CRcarrier R1) (n : nat), + CRmorph f (CRsum un n) == + CRsum (fun n0 : nat => CRmorph f (un n0)) n. +Proof. + induction n. + - reflexivity. + - simpl. rewrite CRmorph_plus, IHn. reflexivity. +Qed. + +Lemma CRmorph_INR : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (n : nat), + CRmorph f (INR n) == INR n. +Proof. + induction n. + - apply CRmorph_rat. + - simpl. unfold INR. + rewrite (CRmorph_proper f _ (1 + CR_of_Q R1 (Z.of_nat n # 1))). + rewrite CRmorph_plus. unfold INR in IHn. + rewrite IHn. rewrite CRmorph_one, <- CR_of_Q_one, <- CR_of_Q_plus. + apply CR_of_Q_morph. rewrite Qinv_plus_distr. + unfold Qeq, Qnum, Qden. do 2 rewrite Z.mul_1_r. + rewrite Nat2Z.inj_succ. rewrite <- Z.add_1_l. reflexivity. + rewrite <- CR_of_Q_one, <- CR_of_Q_plus. + apply CR_of_Q_morph. rewrite Qinv_plus_distr. + unfold Qeq, Qnum, Qden. do 2 rewrite Z.mul_1_r. + rewrite Nat2Z.inj_succ. rewrite <- Z.add_1_l. reflexivity. +Qed. + +Lemma CRmorph_rat_cv + : forall {R1 R2 : ConstructiveReals} + (qn : nat -> Q), + CR_cauchy R1 (fun n => CR_of_Q R1 (qn n)) + -> CR_cauchy R2 (fun n => CR_of_Q R2 (qn n)). +Proof. + intros. intro p. destruct (H p) as [n nmaj]. + exists n. intros. specialize (nmaj i j H0 H1). + unfold CRminus. rewrite <- CR_of_Q_opp, <- CR_of_Q_plus, CR_of_Q_abs. + unfold CRminus in nmaj. rewrite <- CR_of_Q_opp, <- CR_of_Q_plus, CR_of_Q_abs in nmaj. + apply CR_of_Q_le. destruct (Q_dec (Qabs (qn i + - qn j)) (1#p)). + destruct s. apply Qlt_le_weak, q. exfalso. + apply (Qlt_not_le _ _ q). apply (CR_of_Q_lt R1) in q. contradiction. + rewrite q. apply Qle_refl. +Qed. + +Definition CR_Q_limit {R : ConstructiveReals} (x : CRcarrier R) (n:nat) + : { q:Q & x < CR_of_Q R q < x + CR_of_Q R (1 # Pos.of_nat n) }. +Proof. + apply (CR_Q_dense R x (x + CR_of_Q R (1 # Pos.of_nat n))). + rewrite <- (CRplus_0_r x). rewrite CRplus_assoc. + apply CRplus_lt_compat_l. rewrite CRplus_0_l. apply CR_of_Q_pos. + reflexivity. +Qed. + +Lemma CR_Q_limit_cv : forall {R : ConstructiveReals} (x : CRcarrier R), + CR_cv R (fun n => CR_of_Q R (let (q,_) := CR_Q_limit x n in q)) x. +Proof. + intros R x p. exists (Pos.to_nat p). + intros. destruct (CR_Q_limit x i). rewrite CRabs_right. + apply (CRplus_le_reg_r x). unfold CRminus. + rewrite CRplus_assoc, CRplus_opp_l, CRplus_0_r, CRplus_comm. + apply (CRle_trans _ (x + CR_of_Q R (1 # Pos.of_nat i))). + apply CRlt_asym, p0. apply CRplus_le_compat_l, CR_of_Q_le. + unfold Qle, Qnum, Qden. rewrite Z.mul_1_l, Z.mul_1_l. + apply Pos2Z.pos_le_pos, Pos2Nat.inj_le. rewrite Nat2Pos.id. exact H. + destruct i. exfalso. inversion H. pose proof (Pos2Nat.is_pos p). + rewrite H1 in H0. inversion H0. discriminate. + rewrite <- (CRplus_opp_r x). apply CRplus_le_compat_r, CRlt_asym, p0. +Qed. + +(* We call this morphism slow to remind that it should only be used + for proofs, not for computations. *) +Definition SlowMorph {R1 R2 : ConstructiveReals} + : CRcarrier R1 -> CRcarrier R2 + := fun x => let (y,_) := CR_complete R2 _ (CRmorph_rat_cv _ (Rcv_cauchy_mod _ x (CR_Q_limit_cv x))) + in y. + +Lemma CauchyMorph_rat : forall {R1 R2 : ConstructiveReals} (q : Q), + SlowMorph (CR_of_Q R1 q) == CR_of_Q R2 q. +Proof. + intros. unfold SlowMorph. + destruct (CR_complete R2 _ + (CRmorph_rat_cv _ + (Rcv_cauchy_mod + (fun n : nat => CR_of_Q R1 (let (q0, _) := CR_Q_limit (CR_of_Q R1 q) n in q0)) + (CR_of_Q R1 q) (CR_Q_limit_cv (CR_of_Q R1 q))))). + apply (CR_cv_unique _ _ _ c). + intro p. exists (Pos.to_nat p). intros. + destruct (CR_Q_limit (CR_of_Q R1 q) i). rewrite CRabs_right. + apply (CRplus_le_reg_r (CR_of_Q R2 q)). unfold CRminus. + rewrite CRplus_assoc, CRplus_opp_l, CRplus_0_r, CRplus_comm. + rewrite <- CR_of_Q_plus. apply CR_of_Q_le. + destruct (Q_dec x0 (q + (1 # p))%Q). destruct s. + apply Qlt_le_weak, q0. exfalso. pose proof (CR_of_Q_lt R1 _ _ q0). + apply (CRlt_asym _ _ H0). apply (CRlt_le_trans _ _ _ (snd p0)). clear H0. + rewrite <- CR_of_Q_plus. apply CR_of_Q_le. apply Qplus_le_r. + unfold Qle, Qnum, Qden. rewrite Z.mul_1_l, Z.mul_1_l. + apply Pos2Z.pos_le_pos, Pos2Nat.inj_le. rewrite Nat2Pos.id. exact H. + destruct i. exfalso. inversion H. pose proof (Pos2Nat.is_pos p). + rewrite H1 in H0. inversion H0. discriminate. + rewrite q0. apply Qle_refl. + rewrite <- (CRplus_opp_r (CR_of_Q R2 q)). apply CRplus_le_compat_r, CR_of_Q_le. + destruct (Q_dec q x0). destruct s. apply Qlt_le_weak, q0. + exfalso. apply (CRlt_asym _ _ (fst p0)). apply CR_of_Q_lt. exact q0. + rewrite q0. apply Qle_refl. +Qed. + +(* The increasing property of morphisms, when the left bound is rational. *) +Lemma SlowMorph_increasing_Qr + : forall {R1 R2 : ConstructiveReals} (x : CRcarrier R1) (q : Q), + CR_of_Q R1 q < x -> CR_of_Q R2 q < SlowMorph x. +Proof. + intros. + unfold SlowMorph; + destruct (CR_complete R2 _ + (CRmorph_rat_cv _ + (Rcv_cauchy_mod (fun n : nat => CR_of_Q R1 (let (q0, _) := CR_Q_limit x n in q0)) x + (CR_Q_limit_cv x)))). + destruct (CR_Q_dense R1 _ _ H) as [r [H0 H1]]. + apply lt_CR_of_Q in H0. + apply (CRlt_le_trans _ (CR_of_Q R2 r)). + apply CR_of_Q_lt, H0. + assert (forall n:nat, le O n -> CR_of_Q R2 r <= CR_of_Q R2 (let (q0, _) := CR_Q_limit x n in q0)). + { intros. apply CR_of_Q_le. destruct (CR_Q_limit x n). + destruct (Q_dec r x1). destruct s. apply Qlt_le_weak, q0. + exfalso. apply (CR_of_Q_lt R1) in q0. + apply (CRlt_asym _ _ q0). exact (CRlt_trans _ _ _ H1 (fst p)). + rewrite q0. apply Qle_refl. } + exact (CR_cv_bound_down _ _ _ O H2 c). +Qed. + +(* The increasing property of morphisms, when the right bound is rational. *) +Lemma SlowMorph_increasing_Ql + : forall {R1 R2 : ConstructiveReals} (x : CRcarrier R1) (q : Q), + x < CR_of_Q R1 q -> SlowMorph x < CR_of_Q R2 q. +Proof. + intros. + unfold SlowMorph; + destruct (CR_complete R2 _ + (CRmorph_rat_cv _ + (Rcv_cauchy_mod (fun n : nat => CR_of_Q R1 (let (q0, _) := CR_Q_limit x n in q0)) x + (CR_Q_limit_cv x)))). + assert (CR_cv R1 (fun n => CR_of_Q R1 (let (q0, _) := CR_Q_limit x n in q0) + + CR_of_Q R1 (1 # Pos.of_nat n)) x). + { apply (CR_cv_proper _ (x+0)). apply CR_cv_plus. apply CR_Q_limit_cv. + intro p. exists (Pos.to_nat p). intros. + unfold CRminus. rewrite CRopp_0, CRplus_0_r. rewrite CRabs_right. + apply CR_of_Q_le. unfold Qle, Qnum, Qden. do 2 rewrite Z.mul_1_l. + apply Pos2Z.pos_le_pos, Pos2Nat.inj_le. rewrite Nat2Pos.id. exact H0. + destruct i. inversion H0. pose proof (Pos2Nat.is_pos p). + rewrite H2 in H1. inversion H1. discriminate. + rewrite <- CR_of_Q_zero. apply CR_of_Q_le. discriminate. + rewrite CRplus_0_r. reflexivity. } + pose proof (CR_cv_open_above _ _ _ H0 H) as [n nmaj]. + apply (CRle_lt_trans _ (CR_of_Q R2 (let (q0, _) := CR_Q_limit x n in + q0 + (1 # Pos.of_nat n)))). + - apply (CR_cv_bound_up (fun n : nat => CR_of_Q R2 (let (q0, _) := CR_Q_limit x n in q0)) _ _ n). + 2: exact c. intros. destruct (CR_Q_limit x n0), (CR_Q_limit x n). + apply CR_of_Q_le, Qlt_le_weak. apply (lt_CR_of_Q R1). + apply (CRlt_le_trans _ _ _ (snd p)). + apply (CRle_trans _ (CR_of_Q R1 x2 + CR_of_Q R1 (1 # Pos.of_nat n0))). + apply CRplus_le_compat_r. apply CRlt_asym, p0. + rewrite <- CR_of_Q_plus. apply CR_of_Q_le. apply Qplus_le_r. + unfold Qle, Qnum, Qden. do 2 rewrite Z.mul_1_l. + apply Pos2Z.pos_le_pos, Pos2Nat.inj_le. + destruct n. destruct n0. apply le_refl. + rewrite (Nat2Pos.id (S n0)). apply le_n_S, le_0_n. discriminate. + destruct n0. exfalso; inversion H1. + rewrite Nat2Pos.id, Nat2Pos.id. exact H1. discriminate. discriminate. + - specialize (nmaj n (le_refl n)). + destruct (CR_Q_limit x n). apply CR_of_Q_lt. + rewrite <- CR_of_Q_plus in nmaj. apply lt_CR_of_Q in nmaj. exact nmaj. +Qed. + +Lemma SlowMorph_increasing : forall {R1 R2 : ConstructiveReals} (x y : CRcarrier R1), + x < y -> @SlowMorph R1 R2 x < SlowMorph y. +Proof. + intros. + destruct (CR_Q_dense R1 _ _ H) as [q [H0 H1]]. + apply (CRlt_trans _ (CR_of_Q R2 q)). + apply SlowMorph_increasing_Ql. exact H0. + apply SlowMorph_increasing_Qr. exact H1. +Qed. + + +(* We call this morphism slow to remind that it should only be used + for proofs, not for computations. *) +Definition SlowConstructiveRealsMorphism {R1 R2 : ConstructiveReals} + : @ConstructiveRealsMorphism R1 R2 + := Build_ConstructiveRealsMorphism + R1 R2 SlowMorph CauchyMorph_rat + SlowMorph_increasing. + +Lemma CRmorph_abs : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (x : CRcarrier R1), + CRabs R2 (CRmorph f x) == CRmorph f (CRabs R1 x). +Proof. + assert (forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (x : CRcarrier R1), + CRabs R2 (CRmorph f x) <= CRmorph f (CRabs R1 x)). + { intros. rewrite <- CRabs_def. split. + - apply CRmorph_le. + pose proof (CRabs_def _ x (CRabs R1 x)) as [_ H]. + apply H, CRle_refl. + - apply (CRle_trans _ (CRmorph f (CRopp R1 x))). + apply CRmorph_opp. apply CRmorph_le. + pose proof (CRabs_def _ x (CRabs R1 x)) as [_ H]. + apply H, CRle_refl. } + intros. split. 2: apply H. + apply (CRmorph_le_inv (@SlowConstructiveRealsMorphism R2 R1)). + apply (CRle_trans _ (CRabs R1 x)). + apply (Endomorph_id + (CRmorph_compose f (@SlowConstructiveRealsMorphism R2 R1))). + apply (CRle_trans + _ (CRabs R1 (CRmorph (@SlowConstructiveRealsMorphism R2 R1) (CRmorph f x)))). + apply CRabs_morph. + apply CReq_sym, (Endomorph_id + (CRmorph_compose f (@SlowConstructiveRealsMorphism R2 R1))). + apply H. +Qed. + +Lemma CRmorph_cv : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (un : nat -> CRcarrier R1) + (l : CRcarrier R1), + CR_cv R1 un l + -> CR_cv R2 (fun n => CRmorph f (un n)) (CRmorph f l). +Proof. + intros. intro p. specialize (H p) as [n H]. + exists n. intros. specialize (H i H0). + unfold CRminus. rewrite <- CRmorph_opp, <- CRmorph_plus, CRmorph_abs. + rewrite <- (CRmorph_rat f (1#p)). apply CRmorph_le. exact H. +Qed. + +Lemma CRmorph_cauchy_reverse : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (un : nat -> CRcarrier R1), + CR_cauchy R2 (fun n => CRmorph f (un n)) + -> CR_cauchy R1 un. +Proof. + intros. intro p. specialize (H p) as [n H]. + exists n. intros. specialize (H i j H0 H1). + unfold CRminus in H. rewrite <- CRmorph_opp, <- CRmorph_plus, CRmorph_abs in H. + rewrite <- (CRmorph_rat f (1#p)) in H. + apply (CRmorph_le_inv f) in H. exact H. +Qed. + +Lemma CRmorph_min : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (a b : CRcarrier R1), + CRmorph f (CRmin a b) + == CRmin (CRmorph f a) (CRmorph f b). +Proof. + intros. unfold CRmin. + rewrite CRmorph_mult. apply CRmult_morph. + 2: apply CRmorph_rat. + unfold CRminus. do 2 rewrite CRmorph_plus. apply CRplus_morph. + apply CRplus_morph. reflexivity. reflexivity. + rewrite CRmorph_opp. apply CRopp_morph. + rewrite <- CRmorph_abs. apply CRabs_morph. + rewrite CRmorph_plus. apply CRplus_morph. + reflexivity. + rewrite CRmorph_opp. apply CRopp_morph, CRmorph_proper. reflexivity. +Qed. + +Lemma CRmorph_series_cv : forall {R1 R2 : ConstructiveReals} + (f : @ConstructiveRealsMorphism R1 R2) + (un : nat -> CRcarrier R1) + (l : CRcarrier R1), + series_cv un l + -> series_cv (fun n => CRmorph f (un n)) (CRmorph f l). +Proof. + intros. + apply (CR_cv_eq _ (fun n => CRmorph f (CRsum un n))). + intro n. apply CRmorph_sum. + apply CRmorph_cv, H. +Qed. diff --git a/theories/Reals/Abstract/ConstructiveSum.v b/theories/Reals/Abstract/ConstructiveSum.v new file mode 100644 index 0000000000..11c8e5d8a2 --- /dev/null +++ b/theories/Reals/Abstract/ConstructiveSum.v @@ -0,0 +1,348 @@ +(************************************************************************) +(* * The Coq Proof Assistant / The Coq Development Team *) +(* v * INRIA, CNRS and contributors - Copyright 1999-2019 *) +(* <O___,, * (see CREDITS file for the list of authors) *) +(* \VV/ **************************************************************) +(* // * This file is distributed under the terms of the *) +(* * GNU Lesser General Public License Version 2.1 *) +(* * (see LICENSE file for the text of the license) *) +(************************************************************************) + +Require Import QArith Qabs. +Require Import ConstructiveReals. +Require Import ConstructiveAbs. + +Local Open Scope ConstructiveReals. + + +(** + Definition and properties of finite sums and powers. +*) + +Fixpoint CRsum {R : ConstructiveReals} + (f:nat -> CRcarrier R) (N:nat) : CRcarrier R := + match N with + | O => f 0%nat + | S i => CRsum f i + f (S i) + end. + +Fixpoint CRpow {R : ConstructiveReals} (r:CRcarrier R) (n:nat) : CRcarrier R := + match n with + | O => 1 + | S n => r * (CRpow r n) + end. + +Lemma CRsum_eq : + forall {R : ConstructiveReals} (An Bn:nat -> CRcarrier R) (N:nat), + (forall i:nat, (i <= N)%nat -> An i == Bn i) -> + CRsum An N == CRsum Bn N. +Proof. + induction N. + - intros. exact (H O (le_refl _)). + - intros. simpl. apply CRplus_morph. apply IHN. + intros. apply H. apply (le_trans _ N _ H0), le_S, le_refl. + apply H, le_refl. +Qed. + +Lemma sum_eq_R0 : forall {R : ConstructiveReals} (un : nat -> CRcarrier R) (n : nat), + (forall k:nat, un k == 0) + -> CRsum un n == 0. +Proof. + induction n. + - intros. apply H. + - intros. simpl. rewrite IHn. rewrite H. apply CRplus_0_l. exact H. +Qed. + +Definition INR {R : ConstructiveReals} (n : nat) : CRcarrier R + := CR_of_Q R (Z.of_nat n # 1). + +Lemma sum_const : forall {R : ConstructiveReals} (a : CRcarrier R) (n : nat), + CRsum (fun _ => a) n == a * INR (S n). +Proof. + induction n. + - unfold INR. simpl. rewrite CR_of_Q_one, CRmult_1_r. reflexivity. + - simpl. rewrite IHn. unfold INR. + replace (Z.of_nat (S (S n))) with (Z.of_nat (S n) + 1)%Z. + rewrite <- Qinv_plus_distr, CR_of_Q_plus, CRmult_plus_distr_l. + apply CRplus_morph. reflexivity. rewrite CR_of_Q_one, CRmult_1_r. reflexivity. + replace 1%Z with (Z.of_nat 1). rewrite <- Nat2Z.inj_add. + apply f_equal. rewrite Nat.add_comm. reflexivity. reflexivity. +Qed. + +Lemma multiTriangleIneg : forall {R : ConstructiveReals} (u : nat -> CRcarrier R) (n : nat), + CRabs R (CRsum u n) <= CRsum (fun k => CRabs R (u k)) n. +Proof. + induction n. + - apply CRle_refl. + - simpl. apply (CRle_trans _ (CRabs R (CRsum u n) + CRabs R (u (S n)))). + apply CRabs_triang. apply CRplus_le_compat. apply IHn. + apply CRle_refl. +Qed. + +Lemma sum_assoc : forall {R : ConstructiveReals} (u : nat -> CRcarrier R) (n p : nat), + CRsum u (S n + p) + == CRsum u n + CRsum (fun k => u (S n + k)%nat) p. +Proof. + induction p. + - simpl. rewrite Nat.add_0_r. reflexivity. + - simpl. rewrite (Radd_assoc (CRisRing R)). apply CRplus_morph. + rewrite Nat.add_succ_r. + rewrite (CRsum_eq (fun k : nat => u (S (n + k))) (fun k : nat => u (S n + k)%nat)). + rewrite <- IHp. reflexivity. intros. reflexivity. reflexivity. +Qed. + +Lemma sum_Rle : forall {R : ConstructiveReals} (un vn : nat -> CRcarrier R) (n : nat), + (forall k, le k n -> un k <= vn k) + -> CRsum un n <= CRsum vn n. +Proof. + induction n. + - intros. apply H. apply le_refl. + - intros. simpl. apply CRplus_le_compat. apply IHn. + intros. apply H. apply (le_trans _ n _ H0). apply le_S, le_refl. + apply H. apply le_refl. +Qed. + +Lemma Abs_sum_maj : forall {R : ConstructiveReals} (un vn : nat -> CRcarrier R), + (forall n:nat, CRabs R (un n) <= (vn n)) + -> forall n p:nat, (CRabs R (CRsum un n - CRsum un p) <= + CRsum vn (Init.Nat.max n p) - CRsum vn (Init.Nat.min n p)). +Proof. + intros. destruct (le_lt_dec n p). + - destruct (Nat.le_exists_sub n p) as [k [maj _]]. assumption. + subst p. rewrite max_r. rewrite min_l. + setoid_replace (CRsum un n - CRsum un (k + n)) + with (-(CRsum un (k + n) - CRsum un n)). + rewrite CRabs_opp. + destruct k. simpl. unfold CRminus. rewrite CRplus_opp_r. + rewrite CRplus_opp_r. rewrite CRabs_right. + apply CRle_refl. apply CRle_refl. + replace (S k + n)%nat with (S n + k)%nat. + unfold CRminus. rewrite sum_assoc. rewrite sum_assoc. + rewrite CRplus_comm. + rewrite <- CRplus_assoc. rewrite CRplus_opp_l. + rewrite CRplus_0_l. rewrite CRplus_comm. + rewrite <- CRplus_assoc. rewrite CRplus_opp_l. + rewrite CRplus_0_l. + apply (CRle_trans _ (CRsum (fun k0 : nat => CRabs R (un (S n + k0)%nat)) k)). + apply multiTriangleIneg. apply sum_Rle. intros. + apply H. rewrite Nat.add_comm, Nat.add_succ_r. reflexivity. + unfold CRminus. rewrite CRopp_plus_distr, CRopp_involutive, CRplus_comm. + reflexivity. assumption. assumption. + - destruct (Nat.le_exists_sub p n) as [k [maj _]]. unfold lt in l. + apply (le_trans p (S p)). apply le_S. apply le_refl. assumption. + subst n. rewrite max_l. rewrite min_r. + destruct k. simpl. unfold CRminus. rewrite CRplus_opp_r. + rewrite CRplus_opp_r. rewrite CRabs_right. apply CRle_refl. + apply CRle_refl. + replace (S k + p)%nat with (S p + k)%nat. unfold CRminus. + rewrite sum_assoc. rewrite sum_assoc. + rewrite CRplus_comm. + rewrite <- CRplus_assoc. rewrite CRplus_opp_l. + rewrite CRplus_0_l. rewrite CRplus_comm. + rewrite <- CRplus_assoc. rewrite CRplus_opp_l. + rewrite CRplus_0_l. + apply (CRle_trans _ (CRsum (fun k0 : nat => CRabs R (un (S p + k0)%nat)) k)). + apply multiTriangleIneg. apply sum_Rle. intros. + apply H. rewrite Nat.add_comm, Nat.add_succ_r. reflexivity. + apply (le_trans p (S p)). apply le_S. apply le_refl. assumption. + apply (le_trans p (S p)). apply le_S. apply le_refl. assumption. +Qed. + +Lemma cond_pos_sum : forall {R : ConstructiveReals} (un : nat -> CRcarrier R) (n : nat), + (forall k, 0 <= un k) + -> 0 <= CRsum un n. +Proof. + induction n. + - intros. apply H. + - intros. simpl. rewrite <- CRplus_0_r. + apply CRplus_le_compat. apply IHn, H. apply H. +Qed. + +Lemma pos_sum_more : forall {R : ConstructiveReals} (u : nat -> CRcarrier R) + (n p : nat), + (forall k:nat, 0 <= u k) + -> le n p -> CRsum u n <= CRsum u p. +Proof. + intros. destruct (Nat.le_exists_sub n p H0). destruct H1. subst p. + rewrite plus_comm. + destruct x. rewrite plus_0_r. apply CRle_refl. rewrite Nat.add_succ_r. + replace (S (n + x)) with (S n + x)%nat. rewrite sum_assoc. + rewrite <- CRplus_0_r, CRplus_assoc. + apply CRplus_le_compat_l. rewrite CRplus_0_l. + apply cond_pos_sum. + intros. apply H. auto. +Qed. + +Lemma sum_opp : forall {R : ConstructiveReals} (un : nat -> CRcarrier R) (n : nat), + CRsum (fun k => - un k) n == - CRsum un n. +Proof. + induction n. + - reflexivity. + - simpl. rewrite IHn. rewrite CRopp_plus_distr. reflexivity. +Qed. + +Lemma sum_scale : forall {R : ConstructiveReals} (u : nat -> CRcarrier R) (a : CRcarrier R) (n : nat), + CRsum (fun k : nat => u k * a) n == CRsum u n * a. +Proof. + induction n. + - simpl. rewrite (Rmul_comm (CRisRing R)). reflexivity. + - simpl. rewrite IHn. rewrite CRmult_plus_distr_r. + apply CRplus_morph. reflexivity. + rewrite (Rmul_comm (CRisRing R)). reflexivity. +Qed. + +Lemma sum_plus : forall {R : ConstructiveReals} (u v : nat -> CRcarrier R) (n : nat), + CRsum (fun n0 : nat => u n0 + v n0) n == CRsum u n + CRsum v n. +Proof. + induction n. + - reflexivity. + - simpl. rewrite IHn. do 2 rewrite CRplus_assoc. + apply CRplus_morph. reflexivity. rewrite CRplus_comm, CRplus_assoc. + apply CRplus_morph. reflexivity. apply CRplus_comm. +Qed. + +Lemma decomp_sum : + forall {R : ConstructiveReals} (An:nat -> CRcarrier R) (N:nat), + (0 < N)%nat -> + CRsum An N == An 0%nat + CRsum (fun i:nat => An (S i)) (pred N). +Proof. + induction N. + - intros. exfalso. inversion H. + - intros _. destruct N. simpl. reflexivity. simpl. + rewrite IHN. rewrite CRplus_assoc. + apply CRplus_morph. reflexivity. reflexivity. + apply le_n_S, le_0_n. +Qed. + +Lemma reverse_sum : forall {R : ConstructiveReals} (u : nat -> CRcarrier R) (n : nat), + CRsum u n == CRsum (fun k => u (n-k)%nat) n. +Proof. + induction n. + - intros. reflexivity. + - rewrite (decomp_sum (fun k : nat => u (S n - k)%nat)). simpl. + rewrite CRplus_comm. apply CRplus_morph. reflexivity. assumption. + unfold lt. apply le_n_S. apply le_0_n. +Qed. + +Lemma Rplus_le_pos : forall {R : ConstructiveReals} (a b : CRcarrier R), + 0 <= b -> a <= a + b. +Proof. + intros. rewrite <- (CRplus_0_r a). rewrite CRplus_assoc. + apply CRplus_le_compat_l. rewrite CRplus_0_l. assumption. +Qed. + +Lemma selectOneInSum : forall {R : ConstructiveReals} (u : nat -> CRcarrier R) (n i : nat), + le i n + -> (forall k:nat, 0 <= u k) + -> u i <= CRsum u n. +Proof. + induction n. + - intros. inversion H. subst i. apply CRle_refl. + - intros. apply Nat.le_succ_r in H. destruct H. + apply (CRle_trans _ (CRsum u n)). apply IHn. assumption. assumption. + simpl. apply Rplus_le_pos. apply H0. + subst i. simpl. rewrite CRplus_comm. apply Rplus_le_pos. + apply cond_pos_sum. intros. apply H0. +Qed. + +Lemma splitSum : forall {R : ConstructiveReals} (un : nat -> CRcarrier R) + (filter : nat -> bool) (n : nat), + CRsum un n + == CRsum (fun i => if filter i then un i else 0) n + + CRsum (fun i => if filter i then 0 else un i) n. +Proof. + induction n. + - simpl. destruct (filter O). symmetry; apply CRplus_0_r. + symmetry. apply CRplus_0_l. + - simpl. rewrite IHn. clear IHn. destruct (filter (S n)). + do 2 rewrite CRplus_assoc. apply CRplus_morph. reflexivity. + rewrite CRplus_comm. apply CRplus_morph. reflexivity. rewrite CRplus_0_r. + reflexivity. rewrite CRplus_0_r. rewrite CRplus_assoc. reflexivity. +Qed. + + +(* Power *) + +Lemma pow_R1_Rle : forall {R : ConstructiveReals} (x : CRcarrier R) (n : nat), + 1 <= x + -> 1 <= CRpow x n. +Proof. + induction n. + - intros. apply CRle_refl. + - intros. simpl. apply (CRle_trans _ (x * 1)). + rewrite CRmult_1_r. exact H. + apply CRmult_le_compat_l_half. apply (CRlt_le_trans _ 1). + apply CRzero_lt_one. exact H. + apply IHn. exact H. +Qed. + +Lemma pow_le : forall {R : ConstructiveReals} (x : CRcarrier R) (n : nat), + 0 <= x + -> 0 <= CRpow x n. +Proof. + induction n. + - intros. apply CRlt_asym, CRzero_lt_one. + - intros. simpl. apply CRmult_le_0_compat. + exact H. apply IHn. exact H. +Qed. + +Lemma pow_lt : forall {R : ConstructiveReals} (x : CRcarrier R) (n : nat), + 0 < x + -> 0 < CRpow x n. +Proof. + induction n. + - intros. apply CRzero_lt_one. + - intros. simpl. apply CRmult_lt_0_compat. exact H. + apply IHn. exact H. +Qed. + +Lemma pow_mult : forall {R : ConstructiveReals} (x y : CRcarrier R) (n:nat), + CRpow x n * CRpow y n == CRpow (x*y) n. +Proof. + induction n. + - simpl. rewrite CRmult_1_r. reflexivity. + - simpl. rewrite <- IHn. do 2 rewrite <- (Rmul_assoc (CRisRing R)). + apply CRmult_morph. reflexivity. + rewrite <- (Rmul_comm (CRisRing R)). rewrite <- (Rmul_assoc (CRisRing R)). + apply CRmult_morph. reflexivity. + rewrite <- (Rmul_comm (CRisRing R)). reflexivity. +Qed. + +Lemma pow_one : forall {R : ConstructiveReals} (n:nat), + @CRpow R 1 n == 1. +Proof. + induction n. reflexivity. + transitivity (CRmult R 1 (CRpow 1 n)). reflexivity. + rewrite IHn. rewrite CRmult_1_r. reflexivity. +Qed. + +Lemma pow_proper : forall {R : ConstructiveReals} (x y : CRcarrier R) (n : nat), + x == y -> CRpow x n == CRpow y n. +Proof. + induction n. + - intros. reflexivity. + - intros. simpl. rewrite IHn, H. reflexivity. exact H. +Qed. + +Lemma pow_inv : forall {R : ConstructiveReals} (x : CRcarrier R) (xPos : 0 < x) (n : nat), + CRpow (CRinv R x (inr xPos)) n + == CRinv R (CRpow x n) (inr (pow_lt x n xPos)). +Proof. + induction n. + - rewrite CRinv_1. reflexivity. + - transitivity (CRinv R x (inr xPos) * CRpow (CRinv R x (inr xPos)) n). + reflexivity. rewrite IHn. + assert (0 < x * CRpow x n). + { apply CRmult_lt_0_compat. exact xPos. apply pow_lt, xPos. } + rewrite <- (CRinv_mult_distr _ _ _ _ (inr H)). + apply CRinv_morph. reflexivity. +Qed. + +Lemma pow_plus_distr : forall {R : ConstructiveReals} (x : CRcarrier R) (n p:nat), + CRpow x n * CRpow x p == CRpow x (n+p). +Proof. + induction n. + - intros. simpl. rewrite CRmult_1_l. reflexivity. + - intros. simpl. rewrite CRmult_assoc. apply CRmult_morph. + reflexivity. apply IHn. +Qed. diff --git a/theories/Reals/Cauchy/ConstructiveCauchyAbs.v b/theories/Reals/Cauchy/ConstructiveCauchyAbs.v new file mode 100644 index 0000000000..7e51b575ba --- /dev/null +++ b/theories/Reals/Cauchy/ConstructiveCauchyAbs.v @@ -0,0 +1,887 @@ +(************************************************************************) +(* * The Coq Proof Assistant / The Coq Development Team *) +(* v * INRIA, CNRS and contributors - Copyright 1999-2019 *) +(* <O___,, * (see CREDITS file for the list of authors) *) +(* \VV/ **************************************************************) +(* // * This file is distributed under the terms of the *) +(* * GNU Lesser General Public License Version 2.1 *) +(* * (see LICENSE file for the text of the license) *) +(************************************************************************) + +Require Import QArith. +Require Import Qabs. +Require Import ConstructiveCauchyReals. +Require Import ConstructiveCauchyRealsMult. + +Local Open Scope CReal_scope. + + +(** + The constructive formulation of the absolute value on the real numbers. + This is followed by the constructive definitions of minimum and maximum, + as min x y := (x + y - |x-y|) / 2. +*) + + +(* If a rational sequence is Cauchy, then so is its absolute value. + This is how the constructive absolute value is defined. + A more abstract way to put it is the real numbers are the metric completion + of the rational numbers, so the uniformly continuous function + Qabs : Q -> Q + uniquely extends to a uniformly continuous function + CReal_abs : CReal -> CReal +*) +Lemma CauchyAbsStable : forall xn : nat -> Q, + QCauchySeq xn Pos.to_nat + -> QCauchySeq (fun n => Qabs (xn n)) Pos.to_nat. +Proof. + intros xn cau n p q H H0. + specialize (cau n p q H H0). + apply (Qle_lt_trans _ (Qabs (xn p - xn q))). + 2: exact cau. apply Qabs_Qle_condition. split. + 2: apply Qabs_triangle_reverse. + apply (Qplus_le_r _ _ (Qabs (xn q))). + rewrite <- Qabs_opp. + apply (Qle_trans _ _ _ (Qabs_triangle_reverse _ _)). + ring_simplify. + setoid_replace (-xn q - (xn p - xn q))%Q with (-(xn p))%Q. + 2: ring. rewrite Qabs_opp. apply Qle_refl. +Qed. + +Definition CReal_abs (x : CReal) : CReal + := let (xn, cau) := x in + exist _ (fun n => Qabs (xn n)) (CauchyAbsStable xn cau). + +Lemma CReal_neg_nth : forall (x : CReal) (n : positive), + (proj1_sig x (Pos.to_nat n) < -1#n)%Q + -> x < 0. +Proof. + intros. destruct x as [xn cau]; unfold proj1_sig in H. + apply Qlt_minus_iff in H. + setoid_replace ((-1 # n) + - xn (Pos.to_nat n))%Q + with (- ((1 # n) + xn (Pos.to_nat n)))%Q in H. + destruct (Qarchimedean (2 / (-((1#n) + xn (Pos.to_nat n))))) as [k kmaj]. + exists (Pos.max k n). simpl. unfold Qminus; rewrite Qplus_0_l. + specialize (cau n (Pos.to_nat n) (max (Pos.to_nat k) (Pos.to_nat n)) + (le_refl _) (Nat.le_max_r _ _)). + apply (Qle_lt_trans _ (2#k)). + unfold Qle, Qnum, Qden. + apply Z.mul_le_mono_nonneg_l. discriminate. + apply Pos2Z.pos_le_pos, Pos.le_max_l. + rewrite <- Pos2Nat.inj_max in cau. + apply (Qmult_lt_l _ _ (-((1 # n) + xn (Pos.to_nat n)))) in kmaj. + rewrite Qmult_div_r in kmaj. + apply (Qmult_lt_r _ _ (1 # k)) in kmaj. + rewrite <- Qmult_assoc in kmaj. + setoid_replace ((Z.pos k # 1) * (1 # k))%Q with 1%Q in kmaj. + rewrite Qmult_1_r in kmaj. + setoid_replace (2#k)%Q with (2 * (1 # k))%Q. 2: reflexivity. + apply (Qlt_trans _ _ _ kmaj). clear kmaj. + apply (Qplus_lt_l _ _ ((1#n) + xn (Pos.to_nat (Pos.max k n)))). + ring_simplify. rewrite Qplus_comm. + apply (Qle_lt_trans _ (Qabs (xn (Pos.to_nat n) - xn (Pos.to_nat (Pos.max k n))))). + 2: exact cau. + rewrite <- Qabs_opp. + setoid_replace (- (xn (Pos.to_nat n) - xn (Pos.to_nat (Pos.max k n))))%Q + with (xn (Pos.to_nat (Pos.max k n)) + -1 * xn (Pos.to_nat n))%Q. + apply Qle_Qabs. ring. 2: reflexivity. + unfold Qmult, Qeq, Qnum, Qden. + rewrite Z.mul_1_r, Z.mul_1_r, Z.mul_1_l. reflexivity. + 2: exact H. intro abs. rewrite abs in H. exact (Qlt_irrefl 0 H). + setoid_replace (-1 # n)%Q with (-(1#n))%Q. ring. reflexivity. +Qed. + +Lemma CReal_nonneg : forall (x : CReal) (n : positive), + 0 <= x -> (-1#n <= proj1_sig x (Pos.to_nat n))%Q. +Proof. + intros. destruct x as [xn cau]; unfold proj1_sig. + destruct (Qlt_le_dec (xn (Pos.to_nat n)) (-1#n)). + 2: exact q. exfalso. apply H. clear H. + apply (CReal_neg_nth _ n). exact q. +Qed. + +Lemma CReal_abs_right : forall x : CReal, 0 <= x -> CReal_abs x == x. +Proof. + intros. apply CRealEq_diff. intro n. + destruct x as [xn cau]; unfold CReal_abs, proj1_sig. + apply (CReal_nonneg _ n) in H. simpl in H. + rewrite Qabs_pos. + 2: unfold Qminus; rewrite <- Qle_minus_iff; apply Qle_Qabs. + destruct (Qlt_le_dec (xn (Pos.to_nat n)) 0). + - rewrite Qabs_neg. 2: apply Qlt_le_weak, q. + apply Qopp_le_compat in H. + apply (Qmult_le_l _ _ (1#2)). reflexivity. ring_simplify. + setoid_replace ((1 # 2) * (2 # n))%Q with (-(-1#n))%Q. + 2: reflexivity. + setoid_replace ((-2 # 2) * xn (Pos.to_nat n))%Q with (- xn (Pos.to_nat n))%Q. + exact H. ring. + - rewrite Qabs_pos. unfold Qminus. rewrite Qplus_opp_r. discriminate. exact q. +Qed. + +Lemma CReal_le_abs : forall x : CReal, x <= CReal_abs x. +Proof. + intros. intros [n nmaj]. destruct x as [xn cau]; simpl in nmaj. + apply (Qle_not_lt _ _ (Qle_Qabs (xn (Pos.to_nat n)))). + apply Qlt_minus_iff. apply (Qlt_trans _ (2#n)). + reflexivity. exact nmaj. +Qed. + +Lemma CReal_abs_pos : forall x : CReal, 0 <= CReal_abs x. +Proof. + intros. intros [n nmaj]. destruct x as [xn cau]; simpl in nmaj. + apply (Qle_not_lt _ _ (Qabs_nonneg (xn (Pos.to_nat n)))). + apply Qlt_minus_iff. apply (Qlt_trans _ (2#n)). + reflexivity. exact nmaj. +Qed. + +Lemma CReal_abs_opp : forall x : CReal, CReal_abs (-x) == CReal_abs x. +Proof. + intros. apply CRealEq_diff. intro n. + destruct x as [xn cau]; unfold CReal_abs, CReal_opp, proj1_sig. + rewrite Qabs_opp. unfold Qminus. rewrite Qplus_opp_r. + discriminate. +Qed. + +Lemma CReal_abs_left : forall x : CReal, x <= 0 -> CReal_abs x == -x. +Proof. + intros. + apply CReal_opp_ge_le_contravar in H. rewrite CReal_opp_0 in H. + rewrite <- CReal_abs_opp. apply CReal_abs_right, H. +Qed. + +Lemma CReal_abs_appart_0 : forall x : CReal, + 0 < CReal_abs x -> x # 0. +Proof. + intros x [n nmaj]. destruct x as [xn cau]; simpl in nmaj. + destruct (Qlt_le_dec (xn (Pos.to_nat n)) 0). + - left. exists n. simpl. rewrite Qabs_neg in nmaj. + apply (Qlt_le_trans _ _ _ nmaj). ring_simplify. apply Qle_refl. + apply Qlt_le_weak, q. + - right. exists n. simpl. rewrite Qabs_pos in nmaj. + exact nmaj. exact q. +Qed. + +Add Parametric Morphism : CReal_abs + with signature CRealEq ==> CRealEq + as CReal_abs_morph. +Proof. + intros. split. + - intro abs. destruct (CReal_abs_appart_0 y). + apply (CReal_le_lt_trans _ (CReal_abs x)). + apply CReal_abs_pos. apply abs. + rewrite CReal_abs_left, CReal_abs_left, H in abs. + exact (CRealLt_asym _ _ abs abs). apply CRealLt_asym, c. + rewrite H. apply CRealLt_asym, c. + rewrite CReal_abs_right, CReal_abs_right, H in abs. + exact (CRealLt_asym _ _ abs abs). apply CRealLt_asym, c. + rewrite H. apply CRealLt_asym, c. + - intro abs. destruct (CReal_abs_appart_0 x). + apply (CReal_le_lt_trans _ (CReal_abs y)). + apply CReal_abs_pos. apply abs. + rewrite CReal_abs_left, CReal_abs_left, H in abs. + exact (CRealLt_asym _ _ abs abs). apply CRealLt_asym, c. + rewrite <- H. apply CRealLt_asym, c. + rewrite CReal_abs_right, CReal_abs_right, H in abs. + exact (CRealLt_asym _ _ abs abs). apply CRealLt_asym, c. + rewrite <- H. apply CRealLt_asym, c. +Qed. + +Lemma CReal_abs_le : forall a b:CReal, -b <= a <= b -> CReal_abs a <= b. +Proof. + intros a b H [n nmaj]. destruct a as [an cau]; simpl in nmaj. + destruct (Qlt_le_dec (an (Pos.to_nat n)) 0). + - rewrite Qabs_neg in nmaj. destruct H. apply H. clear H H0. + exists n. simpl. + destruct b as [bn caub]; simpl; simpl in nmaj. + unfold Qminus. rewrite Qplus_comm. exact nmaj. + apply Qlt_le_weak, q. + - rewrite Qabs_pos in nmaj. destruct H. apply H0. clear H H0. + exists n. simpl. exact nmaj. exact q. +Qed. + +Lemma CReal_abs_minus_sym : forall x y : CReal, + CReal_abs (x - y) == CReal_abs (y - x). +Proof. + intros x y. setoid_replace (x - y) with (-(y-x)). + rewrite CReal_abs_opp. reflexivity. ring. +Qed. + +Lemma CReal_abs_lt : forall x y : CReal, + CReal_abs x < y -> prod (x < y) (-x < y). +Proof. + split. + - apply (CReal_le_lt_trans _ _ _ (CReal_le_abs x)), H. + - apply (CReal_le_lt_trans _ _ _ (CReal_le_abs (-x))). + rewrite CReal_abs_opp. exact H. +Qed. + +Lemma CReal_abs_triang : forall x y : CReal, + CReal_abs (x + y) <= CReal_abs x + CReal_abs y. +Proof. + intros. apply CReal_abs_le. split. + - setoid_replace (x + y) with (-(-x - y)). 2: ring. + apply CReal_opp_ge_le_contravar. + apply CReal_plus_le_compat; rewrite <- CReal_abs_opp; apply CReal_le_abs. + - apply CReal_plus_le_compat; apply CReal_le_abs. +Qed. + +Lemma CReal_abs_triang_inv : forall x y : CReal, + CReal_abs x - CReal_abs y <= CReal_abs (x - y). +Proof. + intros. apply (CReal_plus_le_reg_l (CReal_abs y)). + ring_simplify. rewrite CReal_plus_comm. + apply (CReal_le_trans _ (CReal_abs (x - y + y))). + setoid_replace (x - y + y) with x. apply CRealLe_refl. ring. + apply CReal_abs_triang. +Qed. + +Lemma CReal_abs_triang_inv2 : forall x y : CReal, + CReal_abs (CReal_abs x - CReal_abs y) <= CReal_abs (x - y). +Proof. + intros. apply CReal_abs_le. split. + 2: apply CReal_abs_triang_inv. + apply (CReal_plus_le_reg_r (CReal_abs y)). ring_simplify. + rewrite CReal_plus_comm, CReal_abs_minus_sym. + apply (CReal_le_trans _ _ _ (CReal_abs_triang_inv y (y-x))). + setoid_replace (y - (y - x)) with x. 2: ring. apply CRealLe_refl. +Qed. + +Lemma CReal_abs_gt : forall x : CReal, + x < CReal_abs x -> x < 0. +Proof. + intros x [n nmaj]. destruct x as [xn cau]; simpl in nmaj. + assert (xn (Pos.to_nat n) < 0)%Q. + { destruct (Qlt_le_dec (xn (Pos.to_nat n)) 0). exact q. + exfalso. rewrite Qabs_pos in nmaj. unfold Qminus in nmaj. + rewrite Qplus_opp_r in nmaj. inversion nmaj. exact q. } + rewrite Qabs_neg in nmaj. 2: apply Qlt_le_weak, H. + apply (CReal_neg_nth _ n). simpl. + ring_simplify in nmaj. + apply (Qplus_lt_l _ _ ((1#n) - xn (Pos.to_nat n))). + apply (Qmult_lt_l _ _ 2). reflexivity. ring_simplify. + setoid_replace (2 * (1 # n))%Q with (2 # n)%Q. 2: reflexivity. + rewrite <- Qplus_assoc. + setoid_replace ((2 # n) + 2 * (-1 # n))%Q with 0%Q. + rewrite Qplus_0_r. exact nmaj. + setoid_replace (2*(-1 # n))%Q with (-(2 # n))%Q. + rewrite Qplus_opp_r. reflexivity. reflexivity. +Qed. + +Lemma Rabs_def1 : forall x y : CReal, + x < y -> -x < y -> CReal_abs x < y. +Proof. + intros. apply CRealLt_above in H. apply CRealLt_above in H0. + destruct H as [i imaj]. destruct H0 as [j jmaj]. + exists (Pos.max i j). destruct x as [xn caux], y as [yn cauy]; simpl. + simpl in imaj, jmaj. + destruct (Qlt_le_dec (xn (Pos.to_nat (Pos.max i j))) 0). + - rewrite Qabs_neg. + specialize (jmaj (Pos.max i j) (Pos.le_max_r _ _)). + apply (Qle_lt_trans _ (2#j)). 2: exact jmaj. + unfold Qle, Qnum, Qden. + apply Z.mul_le_mono_nonneg_l. discriminate. + apply Pos2Z.pos_le_pos, Pos.le_max_r. + apply Qlt_le_weak, q. + - rewrite Qabs_pos. + specialize (imaj (Pos.max i j) (Pos.le_max_l _ _)). + apply (Qle_lt_trans _ (2#i)). 2: exact imaj. + unfold Qle, Qnum, Qden. + apply Z.mul_le_mono_nonneg_l. discriminate. + apply Pos2Z.pos_le_pos, Pos.le_max_l. + apply q. +Qed. + +(* The proof by cases on the signs of x and y applies constructively, + because of the positivity hypotheses. *) +Lemma CReal_abs_mult : forall x y : CReal, + CReal_abs (x * y) == CReal_abs x * CReal_abs y. +Proof. + assert (forall x y : CReal, + x # 0 + -> y # 0 + -> CReal_abs (x * y) == CReal_abs x * CReal_abs y) as prep. + { intros. destruct H, H0. + + rewrite CReal_abs_right, CReal_abs_left, CReal_abs_left. ring. + apply CRealLt_asym, c0. apply CRealLt_asym, c. + setoid_replace (x*y) with (- x * - y). + apply CRealLt_asym, CReal_mult_lt_0_compat. + rewrite <- CReal_opp_0. apply CReal_opp_gt_lt_contravar, c. + rewrite <- CReal_opp_0. apply CReal_opp_gt_lt_contravar, c0. ring. + + rewrite CReal_abs_left, CReal_abs_left, CReal_abs_right. ring. + apply CRealLt_asym, c0. apply CRealLt_asym, c. + rewrite <- (CReal_mult_0_l y). + apply CReal_mult_le_compat_r. + apply CRealLt_asym, c0. apply CRealLt_asym, c. + + rewrite CReal_abs_left, CReal_abs_right, CReal_abs_left. ring. + apply CRealLt_asym, c0. apply CRealLt_asym, c. + rewrite <- (CReal_mult_0_r x). + apply CReal_mult_le_compat_l. + apply CRealLt_asym, c. apply CRealLt_asym, c0. + + rewrite CReal_abs_right, CReal_abs_right, CReal_abs_right. ring. + apply CRealLt_asym, c0. apply CRealLt_asym, c. + apply CRealLt_asym, CReal_mult_lt_0_compat; assumption. } + split. + - intro abs. + assert (0 < CReal_abs x * CReal_abs y). + { apply (CReal_le_lt_trans _ (CReal_abs (x*y))). + apply CReal_abs_pos. exact abs. } + pose proof (CReal_mult_pos_appart_zero _ _ H). + rewrite CReal_mult_comm in H. + apply CReal_mult_pos_appart_zero in H. + destruct H. 2: apply (CReal_abs_pos y c). + destruct H0. 2: apply (CReal_abs_pos x c0). + apply CReal_abs_appart_0 in c. + apply CReal_abs_appart_0 in c0. + rewrite (prep x y) in abs. + exact (CRealLt_asym _ _ abs abs). exact c0. exact c. + - intro abs. + assert (0 < CReal_abs (x * y)). + { apply (CReal_le_lt_trans _ (CReal_abs x * CReal_abs y)). + rewrite <- (CReal_mult_0_l (CReal_abs y)). + apply CReal_mult_le_compat_r. + apply CReal_abs_pos. apply CReal_abs_pos. exact abs. } + apply CReal_abs_appart_0 in H. destruct H. + + apply CReal_opp_gt_lt_contravar in c. + rewrite CReal_opp_0, CReal_opp_mult_distr_l in c. + pose proof (CReal_mult_pos_appart_zero _ _ c). + rewrite CReal_mult_comm in c. + apply CReal_mult_pos_appart_zero in c. + rewrite (prep x y) in abs. + exact (CRealLt_asym _ _ abs abs). + destruct H. left. apply CReal_opp_gt_lt_contravar in c0. + rewrite CReal_opp_involutive, CReal_opp_0 in c0. exact c0. + right. apply CReal_opp_gt_lt_contravar in c0. + rewrite CReal_opp_involutive, CReal_opp_0 in c0. exact c0. + destruct c. right. exact c. left. exact c. + + pose proof (CReal_mult_pos_appart_zero _ _ c). + rewrite CReal_mult_comm in c. + apply CReal_mult_pos_appart_zero in c. + rewrite (prep x y) in abs. + exact (CRealLt_asym _ _ abs abs). + destruct H. right. exact c0. left. exact c0. + destruct c. right. exact c. left. exact c. +Qed. + +Lemma CReal_abs_def2 : forall x a:CReal, + CReal_abs x <= a -> (x <= a) /\ (- a <= x). +Proof. + split. + - exact (CReal_le_trans _ _ _ (CReal_le_abs _) H). + - rewrite <- (CReal_opp_involutive x). + apply CReal_opp_ge_le_contravar. + rewrite <- CReal_abs_opp in H. + exact (CReal_le_trans _ _ _ (CReal_le_abs _) H). +Qed. + + +(* Min and max *) + +Definition CReal_min (x y : CReal) : CReal + := (x + y - CReal_abs (y - x)) * inject_Q (1#2). + +Definition CReal_max (x y : CReal) : CReal + := (x + y + CReal_abs (y - x)) * inject_Q (1#2). + +Add Parametric Morphism : CReal_min + with signature CRealEq ==> CRealEq ==> CRealEq + as CReal_min_morph. +Proof. + intros. unfold CReal_min. + rewrite H, H0. reflexivity. +Qed. + +Add Parametric Morphism : CReal_max + with signature CRealEq ==> CRealEq ==> CRealEq + as CReal_max_morph. +Proof. + intros. unfold CReal_max. + rewrite H, H0. reflexivity. +Qed. + +Lemma CReal_double : forall x:CReal, 2 * x == x + x. +Proof. + intro x. rewrite (inject_Q_plus 1 1). ring. +Qed. + +Lemma CReal_max_lub : forall x y z:CReal, + x <= z -> y <= z -> CReal_max x y <= z. +Proof. + intros. unfold CReal_max. + apply (CReal_mult_le_reg_r 2). apply inject_Q_lt; reflexivity. + rewrite CReal_mult_assoc, <- inject_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CReal_mult_1_r. + apply (CReal_plus_le_reg_l (-x-y)). ring_simplify. + apply CReal_abs_le. split. + - unfold CReal_minus. repeat rewrite CReal_opp_plus_distr. + do 2 rewrite CReal_opp_involutive. + rewrite (CReal_plus_comm x), CReal_plus_assoc. apply CReal_plus_le_compat_l. + apply (CReal_plus_le_reg_l (-x)). + rewrite <- CReal_plus_assoc, CReal_plus_opp_l, CReal_plus_0_l. + rewrite CReal_mult_comm, CReal_double. rewrite CReal_opp_plus_distr. + apply CReal_plus_le_compat; apply CReal_opp_ge_le_contravar; assumption. + - unfold CReal_minus. + rewrite (CReal_plus_comm y), CReal_plus_assoc. apply CReal_plus_le_compat_l. + apply (CReal_plus_le_reg_l y). + rewrite <- CReal_plus_assoc, CReal_plus_opp_r, CReal_plus_0_l. + rewrite CReal_mult_comm, CReal_double. + apply CReal_plus_le_compat; assumption. +Qed. + +Lemma CReal_min_glb : forall x y z:CReal, + z <= x -> z <= y -> z <= CReal_min x y. +Proof. + intros. unfold CReal_min. + apply (CReal_mult_le_reg_r 2). apply inject_Q_lt; reflexivity. + rewrite CReal_mult_assoc, <- inject_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CReal_mult_1_r. + apply (CReal_plus_le_reg_l (CReal_abs(y-x) - (z*2))). ring_simplify. + apply CReal_abs_le. split. + - unfold CReal_minus. repeat rewrite CReal_opp_plus_distr. + rewrite CReal_opp_mult_distr_l, CReal_opp_involutive. + rewrite (CReal_plus_comm (z*2)), (CReal_plus_comm y), CReal_plus_assoc. + apply CReal_plus_le_compat_l, (CReal_plus_le_reg_r y). + rewrite CReal_plus_assoc, CReal_plus_opp_l, CReal_plus_0_r. + rewrite CReal_mult_comm, CReal_double. + apply CReal_plus_le_compat; assumption. + - unfold CReal_minus. + rewrite (CReal_plus_comm y). apply CReal_plus_le_compat. + 2: apply CRealLe_refl. + apply (CReal_plus_le_reg_r (-x)). + rewrite CReal_plus_assoc, CReal_plus_opp_r, CReal_plus_0_r. + rewrite CReal_mult_comm, CReal_double. + apply CReal_plus_le_compat; apply CReal_opp_ge_le_contravar; assumption. +Qed. + +Lemma CReal_max_l : forall x y : CReal, x <= CReal_max x y. +Proof. + intros. unfold CReal_max. + apply (CReal_mult_le_reg_r 2). apply inject_Q_lt; reflexivity. + rewrite CReal_mult_assoc, <- inject_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CReal_mult_1_r. + rewrite CReal_mult_comm, CReal_double. + rewrite CReal_plus_assoc. apply CReal_plus_le_compat_l. + apply (CReal_plus_le_reg_l (-y)). + rewrite <- CReal_plus_assoc, CReal_plus_opp_l, CReal_plus_0_l. + rewrite CReal_abs_minus_sym, CReal_plus_comm. + apply CReal_le_abs. +Qed. + +Lemma CReal_max_r : forall x y : CReal, y <= CReal_max x y. +Proof. + intros. unfold CReal_max. + apply (CReal_mult_le_reg_r 2). apply inject_Q_lt; reflexivity. + rewrite CReal_mult_assoc, <- inject_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CReal_mult_1_r. + rewrite CReal_mult_comm, CReal_double. + rewrite (CReal_plus_comm x). + rewrite CReal_plus_assoc. apply CReal_plus_le_compat_l. + apply (CReal_plus_le_reg_l (-x)). + rewrite <- CReal_plus_assoc, CReal_plus_opp_l, CReal_plus_0_l. + rewrite CReal_plus_comm. apply CReal_le_abs. +Qed. + +Lemma CReal_min_l : forall x y : CReal, CReal_min x y <= x. +Proof. + intros. unfold CReal_min. + apply (CReal_mult_le_reg_r 2). apply inject_Q_lt; reflexivity. + rewrite CReal_mult_assoc, <- inject_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CReal_mult_1_r. + rewrite CReal_mult_comm, CReal_double. + unfold CReal_minus. + rewrite CReal_plus_assoc. apply CReal_plus_le_compat_l. + apply (CReal_plus_le_reg_l (CReal_abs (y + - x)+ -x)). ring_simplify. + rewrite CReal_plus_comm. apply CReal_le_abs. +Qed. + +Lemma CReal_min_r : forall x y : CReal, CReal_min x y <= y. +Proof. + intros. unfold CReal_min. + apply (CReal_mult_le_reg_r 2). apply inject_Q_lt; reflexivity. + rewrite CReal_mult_assoc, <- inject_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CReal_mult_1_r. + rewrite CReal_mult_comm, CReal_double. + unfold CReal_minus. rewrite (CReal_plus_comm x). + rewrite CReal_plus_assoc. apply CReal_plus_le_compat_l. + apply (CReal_plus_le_reg_l (CReal_abs (y + - x)+ -y)). ring_simplify. + fold (y-x). rewrite CReal_abs_minus_sym. + rewrite CReal_plus_comm. apply CReal_le_abs. +Qed. + +Lemma CReal_min_left : forall x y : CReal, + x <= y -> CReal_min x y == x. +Proof. + intros. unfold CReal_min. + apply (CReal_mult_eq_reg_r 2). 2: right; apply inject_Q_lt; reflexivity. + rewrite CReal_mult_assoc, <- inject_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CReal_mult_1_r. + rewrite CReal_mult_comm, CReal_double. + rewrite CReal_abs_right. ring. + rewrite <- (CReal_plus_opp_r x). apply CReal_plus_le_compat. + exact H. apply CRealLe_refl. +Qed. + +Lemma CReal_min_right : forall x y : CReal, + y <= x -> CReal_min x y == y. +Proof. + intros. unfold CReal_min. + apply (CReal_mult_eq_reg_r 2). 2: right; apply inject_Q_lt; reflexivity. + rewrite CReal_mult_assoc, <- inject_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CReal_mult_1_r. + rewrite CReal_mult_comm, CReal_double. + rewrite CReal_abs_left. ring. + rewrite <- (CReal_plus_opp_r x). apply CReal_plus_le_compat. + exact H. apply CRealLe_refl. +Qed. + +Lemma CReal_max_left : forall x y : CReal, + y <= x -> CReal_max x y == x. +Proof. + intros. unfold CReal_max. + apply (CReal_mult_eq_reg_r 2). 2: right; apply inject_Q_lt; reflexivity. + rewrite CReal_mult_assoc, <- inject_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CReal_mult_1_r. + rewrite CReal_mult_comm, CReal_double. + rewrite CReal_abs_left. ring. + rewrite <- (CReal_plus_opp_r x). apply CReal_plus_le_compat. + exact H. apply CRealLe_refl. +Qed. + +Lemma CReal_max_right : forall x y : CReal, + x <= y -> CReal_max x y == y. +Proof. + intros. unfold CReal_max. + apply (CReal_mult_eq_reg_r 2). 2: right; apply inject_Q_lt; reflexivity. + rewrite CReal_mult_assoc, <- inject_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CReal_mult_1_r. + rewrite CReal_mult_comm, CReal_double. + rewrite CReal_abs_right. ring. + rewrite <- (CReal_plus_opp_r x). apply CReal_plus_le_compat. + exact H. apply CRealLe_refl. +Qed. + +Lemma CReal_min_lt_r : forall x y : CReal, + CReal_min x y < y -> CReal_min x y == x. +Proof. + intros. unfold CReal_min. unfold CReal_min in H. + apply (CReal_mult_eq_reg_r 2). 2: right; apply inject_Q_lt; reflexivity. + rewrite CReal_mult_assoc, <- inject_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CReal_mult_1_r. + rewrite CReal_mult_comm, CReal_double. + rewrite CReal_abs_right. ring. + apply (CReal_mult_lt_compat_r 2) in H. 2: apply inject_Q_lt; reflexivity. + rewrite CReal_mult_assoc, <- inject_Q_mult in H. + setoid_replace ((1 # 2) * 2)%Q with 1%Q in H. 2: reflexivity. + rewrite CReal_mult_1_r in H. + rewrite CReal_mult_comm, CReal_double in H. + intro abs. rewrite CReal_abs_left in H. + unfold CReal_minus in H. + rewrite CReal_opp_involutive, CReal_plus_comm in H. + rewrite CReal_plus_assoc, <- (CReal_plus_assoc (-x)), CReal_plus_opp_l in H. + rewrite CReal_plus_0_l in H. exact (CRealLt_asym _ _ H H). + apply CRealLt_asym, abs. +Qed. + +Lemma posPartAbsMax : forall x : CReal, + CReal_max 0 x == (x + CReal_abs x) * (inject_Q (1#2)). +Proof. + split. + - intro abs. apply (CReal_mult_lt_compat_r 2) in abs. + 2: apply (inject_Q_lt 0 2); reflexivity. + rewrite CReal_mult_assoc, <- (inject_Q_mult) in abs. + setoid_replace ((1 # 2) * 2)%Q with 1%Q in abs. 2: reflexivity. + rewrite CReal_mult_1_r in abs. + apply (CReal_plus_lt_compat_l (-x)) in abs. + rewrite <- CReal_plus_assoc, CReal_plus_opp_l, CReal_plus_0_l in abs. + apply CReal_abs_le in abs. exact abs. split. + + rewrite CReal_opp_plus_distr, CReal_opp_involutive. + apply (CReal_le_trans _ (x + 0)). 2: rewrite CReal_plus_0_r; apply CRealLe_refl. + apply CReal_plus_le_compat_l. apply (CReal_le_trans _ (2 * 0)). + rewrite CReal_opp_mult_distr_l, <- (CReal_mult_comm 2). apply CReal_mult_le_compat_l_half. + apply inject_Q_lt. reflexivity. + apply (CReal_plus_le_reg_l (CReal_max 0 x)). rewrite CReal_plus_opp_r, CReal_plus_0_r. + apply CReal_max_l. rewrite CReal_mult_0_r. apply CRealLe_refl. + + apply (CReal_plus_le_reg_l x). + rewrite <- CReal_plus_assoc, CReal_plus_opp_r, CReal_plus_0_l. + rewrite (inject_Q_plus 1 1), CReal_mult_plus_distr_l, CReal_mult_1_r. + apply CReal_plus_le_compat; apply CReal_max_r. + - apply CReal_max_lub. rewrite <- (CReal_mult_0_l (inject_Q (1#2))). + do 2 rewrite <- (CReal_mult_comm (inject_Q (1#2))). + apply CReal_mult_le_compat_l_half. + apply inject_Q_lt; reflexivity. + rewrite <- (CReal_plus_opp_r x). apply CReal_plus_le_compat_l. + rewrite <- CReal_abs_opp. apply CReal_le_abs. + intros abs. + apply (CReal_mult_lt_compat_r 2) in abs. 2: apply inject_Q_lt; reflexivity. + rewrite CReal_mult_assoc, <- inject_Q_mult in abs. + setoid_replace ((1 # 2) * 2)%Q with 1%Q in abs. 2: reflexivity. + rewrite CReal_mult_1_r, (inject_Q_plus 1 1), CReal_mult_plus_distr_l, CReal_mult_1_r in abs. + apply CReal_plus_lt_reg_l in abs. + exact (CReal_le_abs x abs). +Qed. + +Lemma negPartAbsMin : forall x : CReal, + CReal_min 0 x == (x - CReal_abs x) * (inject_Q (1#2)). +Proof. + split. + - intro abs. apply (CReal_mult_lt_compat_r 2) in abs. + 2: apply (inject_Q_lt 0 2); reflexivity. + rewrite CReal_mult_assoc, <- (inject_Q_mult) in abs. + setoid_replace ((1 # 2) * 2)%Q with 1%Q in abs. 2: reflexivity. + rewrite CReal_mult_1_r in abs. + apply (CReal_plus_lt_compat_r (CReal_abs x)) in abs. + unfold CReal_minus in abs. + rewrite CReal_plus_assoc, CReal_plus_opp_l, CReal_plus_0_r in abs. + apply (CReal_plus_lt_compat_l (-(CReal_min 0 x * 2))) in abs. + rewrite <- CReal_plus_assoc, CReal_plus_opp_l, CReal_plus_0_l in abs. + apply CReal_abs_lt in abs. destruct abs. + apply (CReal_plus_lt_compat_l (CReal_min 0 x * 2)) in c0. + rewrite <- CReal_plus_assoc, CReal_plus_opp_r, CReal_plus_0_l in c0. + apply (CReal_plus_lt_compat_r x) in c0. + rewrite CReal_plus_assoc, CReal_plus_opp_l, CReal_plus_0_r in c0. + rewrite <- CReal_double, CReal_mult_comm in c0. apply CReal_mult_lt_reg_l in c0. + apply CReal_min_lt_r in c0. + rewrite c0, CReal_mult_0_l, CReal_opp_0, CReal_plus_0_l in c. + exact (CRealLt_asym _ _ c c). apply inject_Q_lt; reflexivity. + - intro abs. + assert ((x - CReal_abs x) * inject_Q (1 # 2) < 0 * inject_Q (1 # 2)). + { rewrite CReal_mult_0_l. + apply (CReal_lt_le_trans _ _ _ abs). apply CReal_min_l. } + apply CReal_mult_lt_reg_r in H. + 2: apply inject_Q_lt; reflexivity. + rewrite <- (CReal_plus_opp_r (CReal_abs x)) in H. + apply CReal_plus_lt_reg_r, CReal_abs_gt in H. + rewrite CReal_min_right, <- CReal_abs_opp, CReal_abs_right in abs. + unfold CReal_minus in abs. + rewrite CReal_opp_involutive, <- CReal_double, CReal_mult_comm in abs. + rewrite <- CReal_mult_assoc, <- inject_Q_mult in abs. + setoid_replace ((1 # 2) * 2)%Q with 1%Q in abs. + rewrite CReal_mult_1_l in abs. exact (CRealLt_asym _ _ abs abs). + reflexivity. rewrite <- CReal_opp_0. + apply CReal_opp_ge_le_contravar, CRealLt_asym, H. + apply CRealLt_asym, H. +Qed. + +Lemma CReal_min_sym : forall (x y : CReal), + CReal_min x y == CReal_min y x. +Proof. + intros. unfold CReal_min. + rewrite CReal_abs_minus_sym. ring. +Qed. + +Lemma CReal_max_sym : forall (x y : CReal), + CReal_max x y == CReal_max y x. +Proof. + intros. unfold CReal_max. + rewrite CReal_abs_minus_sym. ring. +Qed. + +Lemma CReal_min_mult : + forall (p q r:CReal), 0 <= r -> CReal_min (r * p) (r * q) == r * CReal_min p q. +Proof. + intros p q r H. unfold CReal_min. + setoid_replace (r * q - r * p) with (r * (q - p)). + 2: ring. rewrite CReal_abs_mult. + rewrite (CReal_abs_right r). ring. exact H. +Qed. + +Lemma CReal_min_plus : forall (x y z : CReal), + x + CReal_min y z == CReal_min (x + y) (x + z). +Proof. + intros. unfold CReal_min. + setoid_replace (x + z - (x + y)) with (z-y). + 2: ring. + apply (CReal_mult_eq_reg_r 2). 2: right; apply inject_Q_lt; reflexivity. + rewrite CReal_mult_plus_distr_r. + rewrite CReal_mult_assoc, <- inject_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CReal_mult_1_r. + rewrite CReal_mult_assoc, <- inject_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CReal_mult_1_r. + rewrite CReal_mult_comm, CReal_double. ring. +Qed. + +Lemma CReal_max_plus : forall (x y z : CReal), + x + CReal_max y z == CReal_max (x + y) (x + z). +Proof. + intros. unfold CReal_max. + setoid_replace (x + z - (x + y)) with (z-y). + 2: ring. + apply (CReal_mult_eq_reg_r 2). 2: right; apply inject_Q_lt; reflexivity. + rewrite CReal_mult_plus_distr_r. + rewrite CReal_mult_assoc, <- inject_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CReal_mult_1_r. + rewrite CReal_mult_assoc, <- inject_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CReal_mult_1_r. + rewrite CReal_mult_comm, CReal_double. ring. +Qed. + +Lemma CReal_min_lt : forall x y z : CReal, + z < x -> z < y -> z < CReal_min x y. +Proof. + intros. unfold CReal_min. + apply (CReal_mult_lt_reg_r 2). apply inject_Q_lt; reflexivity. + rewrite CReal_mult_assoc, <- inject_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CReal_mult_1_r. + apply (CReal_plus_lt_reg_l (CReal_abs (y - x) - (z*2))). + ring_simplify. apply Rabs_def1. + - unfold CReal_minus. rewrite <- (CReal_plus_comm y). + apply CReal_plus_lt_compat_l. + apply (CReal_plus_lt_reg_r (-x)). + rewrite CReal_plus_assoc, CReal_plus_opp_r, CReal_plus_0_r. + rewrite <- CReal_double, CReal_mult_comm. apply CReal_mult_lt_compat_r. + apply inject_Q_lt; reflexivity. + apply CReal_opp_gt_lt_contravar, H. + - unfold CReal_minus. rewrite CReal_opp_plus_distr, CReal_opp_involutive. + rewrite CReal_plus_comm, (CReal_plus_comm (-z*2)), CReal_plus_assoc. + apply CReal_plus_lt_compat_l. + apply (CReal_plus_lt_reg_r (-y)). + rewrite CReal_plus_assoc, CReal_plus_opp_r, CReal_plus_0_r. + rewrite <- CReal_double, CReal_mult_comm. apply CReal_mult_lt_compat_r. + apply inject_Q_lt; reflexivity. + apply CReal_opp_gt_lt_contravar, H0. +Qed. + +Lemma CReal_max_assoc : forall a b c : CReal, + CReal_max a (CReal_max b c) == CReal_max (CReal_max a b) c. +Proof. + split. + - apply CReal_max_lub. + + apply CReal_max_lub. apply CReal_max_l. + apply (CReal_le_trans _ (CReal_max b c)). + apply CReal_max_l. apply CReal_max_r. + + apply (CReal_le_trans _ (CReal_max b c)). + apply CReal_max_r. apply CReal_max_r. + - apply CReal_max_lub. + + apply (CReal_le_trans _ (CReal_max a b)). + apply CReal_max_l. apply CReal_max_l. + + apply CReal_max_lub. + apply (CReal_le_trans _ (CReal_max a b)). + apply CReal_max_r. apply CReal_max_l. apply CReal_max_r. +Qed. + +Lemma CReal_min_max_mult_neg : + forall (p q r:CReal), r <= 0 -> CReal_min (r * p) (r * q) == r * CReal_max p q. +Proof. + intros p q r H. unfold CReal_min, CReal_max. + setoid_replace (r * q - r * p) with (r * (q - p)). + 2: ring. rewrite CReal_abs_mult. + rewrite (CReal_abs_left r). ring. exact H. +Qed. + +Lemma CReal_min_assoc : forall a b c : CReal, + CReal_min a (CReal_min b c) == CReal_min (CReal_min a b) c. +Proof. + split. + - apply CReal_min_glb. + + apply (CReal_le_trans _ (CReal_min a b)). + apply CReal_min_l. apply CReal_min_l. + + apply CReal_min_glb. + apply (CReal_le_trans _ (CReal_min a b)). + apply CReal_min_l. apply CReal_min_r. apply CReal_min_r. + - apply CReal_min_glb. + + apply CReal_min_glb. apply CReal_min_l. + apply (CReal_le_trans _ (CReal_min b c)). + apply CReal_min_r. apply CReal_min_l. + + apply (CReal_le_trans _ (CReal_min b c)). + apply CReal_min_r. apply CReal_min_r. +Qed. + +Lemma CReal_max_lub_lt : forall x y z : CReal, + x < z -> y < z -> CReal_max x y < z. +Proof. + intros. unfold CReal_max. + apply (CReal_mult_lt_reg_r 2). apply inject_Q_lt; reflexivity. + rewrite CReal_mult_assoc, <- inject_Q_mult. + setoid_replace ((1 # 2) * 2)%Q with 1%Q. 2: reflexivity. + rewrite CReal_mult_1_r. + apply (CReal_plus_lt_reg_l (-x -y)). ring_simplify. + apply Rabs_def1. + - unfold CReal_minus. rewrite (CReal_plus_comm y), CReal_plus_assoc. + apply CReal_plus_lt_compat_l. + apply (CReal_plus_lt_reg_l y). + rewrite <- CReal_plus_assoc, CReal_plus_opp_r, CReal_plus_0_l. + rewrite <- CReal_double, CReal_mult_comm. apply CReal_mult_lt_compat_r. + apply inject_Q_lt; reflexivity. exact H0. + - unfold CReal_minus. rewrite CReal_opp_plus_distr, CReal_opp_involutive. + rewrite (CReal_plus_comm (-x)), CReal_plus_assoc. + apply CReal_plus_lt_compat_l. + apply (CReal_plus_lt_reg_l x). + rewrite <- CReal_plus_assoc, CReal_plus_opp_r, CReal_plus_0_l. + rewrite <- CReal_double, CReal_mult_comm. apply CReal_mult_lt_compat_r. + apply inject_Q_lt; reflexivity. + apply H. +Qed. + +Lemma CReal_max_contract : forall x y a : CReal, + CReal_abs (CReal_max x a - CReal_max y a) + <= CReal_abs (x - y). +Proof. + intros. unfold CReal_max. + rewrite (CReal_abs_morph + _ ((x - y + (CReal_abs (a - x) - CReal_abs (a - y))) * inject_Q (1 # 2))). + 2: ring. + rewrite CReal_abs_mult, (CReal_abs_right (inject_Q (1 # 2))). + 2: apply inject_Q_le; discriminate. + apply (CReal_le_trans + _ ((CReal_abs (x - y) * 1 + CReal_abs (x-y) * 1) + * inject_Q (1 # 2))). + apply CReal_mult_le_compat_r. apply inject_Q_le. discriminate. + apply (CReal_le_trans _ (CReal_abs (x - y) + CReal_abs (CReal_abs (a - x) - CReal_abs (a - y)))). + apply CReal_abs_triang. rewrite CReal_mult_1_r. apply CReal_plus_le_compat_l. + rewrite (CReal_abs_minus_sym x y). + rewrite (CReal_abs_morph (y-x) ((a-x)-(a-y))). + apply CReal_abs_triang_inv2. + unfold CReal_minus. rewrite (CReal_plus_comm (a + - x)). + rewrite <- CReal_plus_assoc. apply CReal_plus_morph. 2: reflexivity. + rewrite CReal_plus_comm, CReal_opp_plus_distr, <- CReal_plus_assoc. + rewrite CReal_plus_opp_r, CReal_opp_involutive, CReal_plus_0_l. + reflexivity. + rewrite <- CReal_mult_plus_distr_l, <- inject_Q_plus. + rewrite CReal_mult_assoc, <- inject_Q_mult. + setoid_replace ((1 + 1) * (1 # 2))%Q with 1%Q. 2: reflexivity. + rewrite CReal_mult_1_r. apply CRealLe_refl. +Qed. + +Lemma CReal_min_contract : forall x y a : CReal, + CReal_abs (CReal_min x a - CReal_min y a) + <= CReal_abs (x - y). +Proof. + intros. unfold CReal_min. + rewrite (CReal_abs_morph + _ ((x - y + (CReal_abs (a - y) - CReal_abs (a - x))) * inject_Q (1 # 2))). + 2: ring. + rewrite CReal_abs_mult, (CReal_abs_right (inject_Q (1 # 2))). + 2: apply inject_Q_le; discriminate. + apply (CReal_le_trans + _ ((CReal_abs (x - y) * 1 + CReal_abs (x-y) * 1) + * inject_Q (1 # 2))). + apply CReal_mult_le_compat_r. apply inject_Q_le. discriminate. + apply (CReal_le_trans _ (CReal_abs (x - y) + CReal_abs (CReal_abs (a - y) - CReal_abs (a - x)))). + apply CReal_abs_triang. rewrite CReal_mult_1_r. apply CReal_plus_le_compat_l. + rewrite (CReal_abs_morph (x-y) ((a-y)-(a-x))). + apply CReal_abs_triang_inv2. + unfold CReal_minus. rewrite (CReal_plus_comm (a + - y)). + rewrite <- CReal_plus_assoc. apply CReal_plus_morph. 2: reflexivity. + rewrite CReal_plus_comm, CReal_opp_plus_distr, <- CReal_plus_assoc. + rewrite CReal_plus_opp_r, CReal_opp_involutive, CReal_plus_0_l. + reflexivity. + rewrite <- CReal_mult_plus_distr_l, <- inject_Q_plus. + rewrite CReal_mult_assoc, <- inject_Q_mult. + setoid_replace ((1 + 1) * (1 # 2))%Q with 1%Q. 2: reflexivity. + rewrite CReal_mult_1_r. apply CRealLe_refl. +Qed. diff --git a/theories/Reals/ConstructiveCauchyReals.v b/theories/Reals/Cauchy/ConstructiveCauchyReals.v index 62e42a7ef3..167f8d41c9 100644 --- a/theories/Reals/ConstructiveCauchyReals.v +++ b/theories/Reals/Cauchy/ConstructiveCauchyReals.v @@ -275,12 +275,6 @@ Proof. pose proof (Pos2Nat.is_pos n). rewrite abs in H. inversion H. Qed. -(* Alias the quotient order equality *) -Definition CRealEq (x y : CReal) : Prop - := (CRealLt x y -> False) /\ (CRealLt y x -> False). - -Infix "==" := CRealEq : CReal_scope. - (* Alias the large order *) Definition CRealLe (x y : CReal) : Prop := CRealLt y x -> False. @@ -295,6 +289,12 @@ Notation "x <= y < z" := (prod (x <= y) (y < z)) : CReal_scope. Notation "x < y < z" := (prod (x < y) (y < z)) : CReal_scope. Notation "x < y <= z" := (prod (x < y) (y <= z)) : CReal_scope. +(* Alias the quotient order equality *) +Definition CRealEq (x y : CReal) : Prop + := (CRealLe y x) /\ (CRealLe x y). + +Infix "==" := CRealEq : CReal_scope. + Lemma CRealLe_not_lt : forall x y : CReal, (forall n:positive, Qle (proj1_sig x (Pos.to_nat n) - proj1_sig y (Pos.to_nat n)) (2 # n)) @@ -322,13 +322,16 @@ Proof. setoid_replace (- (proj1_sig x (Pos.to_nat n) - proj1_sig y (Pos.to_nat n))) with (proj1_sig y (Pos.to_nat n) - proj1_sig x (Pos.to_nat n)). apply H2. assumption. ring. - - intros. split. apply CRealLe_not_lt. intro n. specialize (H n). - rewrite Qabs_Qminus in H. - apply (Qle_trans _ (Qabs (proj1_sig y (Pos.to_nat n) - proj1_sig x (Pos.to_nat n)))). - apply Qle_Qabs. apply H. - apply CRealLe_not_lt. intro n. specialize (H n). - apply (Qle_trans _ (Qabs (proj1_sig x (Pos.to_nat n) - proj1_sig y (Pos.to_nat n)))). - apply Qle_Qabs. apply H. + - intros. split. + + apply CRealLe_not_lt. intro n. specialize (H n). + rewrite Qabs_Qminus in H. + apply (Qle_trans _ (Qabs (proj1_sig y (Pos.to_nat n) + - proj1_sig x (Pos.to_nat n)))). + apply Qle_Qabs. apply H. + + apply CRealLe_not_lt. intro n. specialize (H n). + apply (Qle_trans _ (Qabs (proj1_sig x (Pos.to_nat n) + - proj1_sig y (Pos.to_nat n)))). + apply Qle_Qabs. apply H. Qed. (* The equality on Cauchy reals is just QSeqEquiv, diff --git a/theories/Reals/ConstructiveCauchyRealsMult.v b/theories/Reals/Cauchy/ConstructiveCauchyRealsMult.v index 7530a8f1ef..fa24bd988e 100644 --- a/theories/Reals/ConstructiveCauchyRealsMult.v +++ b/theories/Reals/Cauchy/ConstructiveCauchyRealsMult.v @@ -15,7 +15,7 @@ Require Import QArith. Require Import Qabs. Require Import Qround. Require Import Logic.ConstructiveEpsilon. -Require Export Reals.ConstructiveCauchyReals. +Require Export ConstructiveCauchyReals. Require CMorphisms. Local Open Scope CReal_scope. @@ -1413,3 +1413,91 @@ Proof. destruct (QCauchySeq_bounded (fun _ : nat => r) Pos.to_nat (ConstCauchy r)). simpl in maj. ring_simplify in maj. discriminate maj. Qed. + +Definition Rup_nat (x : CReal) + : { n : nat & x < inject_Q (Z.of_nat n #1) }. +Proof. + intros. destruct (CRealArchimedean x) as [p maj]. + destruct p. + - exists O. apply maj. + - exists (Pos.to_nat p). rewrite positive_nat_Z. apply maj. + - exists O. apply (CReal_lt_trans _ (inject_Q (Z.neg p # 1))). + apply maj. apply inject_Q_lt. reflexivity. +Qed. + +Lemma CReal_mult_le_0_compat : forall (a b : CReal), + 0 <= a -> 0 <= b -> 0 <= a * b. +Proof. + (* Limit of (a + 1/n)*b when n -> infty. *) + intros. intro abs. + assert (0 < -(a*b)) as epsPos. + { rewrite <- CReal_opp_0. apply CReal_opp_gt_lt_contravar. exact abs. } + destruct (Rup_nat (b * (/ (-(a*b))) (inr epsPos))) + as [n maj]. + destruct n as [|n]. + - apply (CReal_mult_lt_compat_r (-(a*b))) in maj. + rewrite CReal_mult_0_l, CReal_mult_assoc, CReal_inv_l, CReal_mult_1_r in maj. + contradiction. exact epsPos. + - (* n > 0 *) + assert (0 < inject_Q (Z.of_nat (S n) #1)) as nPos. + { apply inject_Q_lt. unfold Qlt, Qnum, Qden. + do 2 rewrite Z.mul_1_r. apply Z2Nat.inj_lt. discriminate. + apply Zle_0_nat. rewrite Nat2Z.id. apply le_n_S, le_0_n. } + assert (b * (/ inject_Q (Z.of_nat (S n) #1)) (inr nPos) < -(a*b)). + { apply (CReal_mult_lt_reg_r (inject_Q (Z.of_nat (S n) #1))). apply nPos. + rewrite CReal_mult_assoc, CReal_inv_l, CReal_mult_1_r. + apply (CReal_mult_lt_compat_r (-(a*b))) in maj. + rewrite CReal_mult_assoc, CReal_inv_l, CReal_mult_1_r in maj. + rewrite CReal_mult_comm. apply maj. apply epsPos. } + pose proof (CReal_mult_le_compat_l_half + (a + (/ inject_Q (Z.of_nat (S n) #1)) (inr nPos)) 0 b). + assert (0 + 0 < a + (/ inject_Q (Z.of_nat (S n) #1)) (inr nPos)). + { apply CReal_plus_le_lt_compat. apply H. apply CReal_inv_0_lt_compat. apply nPos. } + rewrite CReal_plus_0_l in H3. specialize (H2 H3 H0). + clear H3. rewrite CReal_mult_0_r in H2. + apply H2. clear H2. rewrite CReal_mult_plus_distr_r. + apply (CReal_plus_lt_compat_l (a*b)) in H1. + rewrite CReal_plus_opp_r in H1. + rewrite (CReal_mult_comm ((/ inject_Q (Z.of_nat (S n) #1)) (inr nPos))). + apply H1. +Qed. + +Lemma CReal_mult_le_compat_l : forall (r r1 r2:CReal), + 0 <= r -> r1 <= r2 -> r * r1 <= r * r2. +Proof. + intros. apply (CReal_plus_le_reg_r (-(r*r1))). + rewrite CReal_plus_opp_r, CReal_opp_mult_distr_r. + rewrite <- CReal_mult_plus_distr_l. + apply CReal_mult_le_0_compat. exact H. + apply (CReal_plus_le_reg_r r1). + rewrite CReal_plus_0_l, CReal_plus_assoc, CReal_plus_opp_l, CReal_plus_0_r. + exact H0. +Qed. + +Lemma CReal_mult_le_compat_r : forall (r r1 r2:CReal), + 0 <= r -> r1 <= r2 -> r1 * r <= r2 * r. +Proof. + intros. apply (CReal_plus_le_reg_r (-(r1*r))). + rewrite CReal_plus_opp_r, CReal_opp_mult_distr_l. + rewrite <- CReal_mult_plus_distr_r. + apply CReal_mult_le_0_compat. 2: exact H. + apply (CReal_plus_le_reg_r r1). ring_simplify. exact H0. +Qed. + +Lemma CReal_mult_le_reg_l : + forall x y z : CReal, + 0 < x -> x * y <= x * z -> y <= z. +Proof. + intros. intro abs. + apply (CReal_mult_lt_compat_l x) in abs. contradiction. + exact H. +Qed. + +Lemma CReal_mult_le_reg_r : + forall x y z : CReal, + 0 < x -> y * x <= z * x -> y <= z. +Proof. + intros. intro abs. + apply (CReal_mult_lt_compat_r x) in abs. contradiction. + exact H. +Qed. diff --git a/theories/Reals/ConstructiveRcomplete.v b/theories/Reals/Cauchy/ConstructiveRcomplete.v index 7d743e464e..51fd0dd7f9 100644 --- a/theories/Reals/ConstructiveRcomplete.v +++ b/theories/Reals/Cauchy/ConstructiveRcomplete.v @@ -14,52 +14,76 @@ Require Import Qabs. Require Import ConstructiveReals. Require Import ConstructiveCauchyRealsMult. Require Import Logic.ConstructiveEpsilon. +Require Import ConstructiveCauchyAbs. Local Open Scope CReal_scope. -Definition absLe (a b : CReal) : Prop - := -b <= a <= b. +(* We use <= in sort Prop rather than < in sort Set, + it is equivalent for the definition of limits and it + extracts smaller programs. *) +Definition seq_cv (un : nat -> CReal) (l : CReal) : Set + := forall p : positive, + { n : nat | forall i:nat, le n i -> CReal_abs (un i - l) <= inject_Q (1#p) }. -Lemma CReal_absSmall : forall (x y : CReal) (n : positive), - (Qlt (2 # n) - (proj1_sig x (Pos.to_nat n) - Qabs (proj1_sig y (Pos.to_nat n)))) - -> absLe y x. +Definition Un_cauchy_mod (un : nat -> CReal) : Set + := forall p : positive, + { n : nat | forall i j:nat, le n i -> le n j + -> CReal_abs (un i - un j) <= inject_Q (1#p) }. + +Lemma seq_cv_proper : forall (un : nat -> CReal) (a b : CReal), + seq_cv un a + -> a == b + -> seq_cv un b. Proof. - intros x y n maj. split. - - apply CRealLt_asym. exists n. destruct x as [xn caux], y as [yn cauy]; simpl. - simpl in maj. unfold Qminus. rewrite Qopp_involutive. - rewrite Qplus_comm. - apply (Qlt_le_trans _ (xn (Pos.to_nat n) - Qabs (yn (Pos.to_nat n)))). - apply maj. apply Qplus_le_r. - rewrite <- (Qopp_involutive (yn (Pos.to_nat n))). - apply Qopp_le_compat. rewrite Qabs_opp. apply Qle_Qabs. - - apply CRealLt_asym. exists n. destruct x as [xn caux], y as [yn cauy]; simpl. - simpl in maj. - apply (Qlt_le_trans _ (xn (Pos.to_nat n) - Qabs (yn (Pos.to_nat n)))). - apply maj. apply Qplus_le_r. apply Qopp_le_compat. apply Qle_Qabs. + intros. intro p. specialize (H p) as [n H]. + exists n. intros. rewrite <- H0. apply H, H1. Qed. -(* We use absLe in sort Prop rather than Set, - to extract smaller programs. *) -Definition Un_cv_mod (un : nat -> CReal) (l : CReal) : Set - := forall p : positive, - { n : nat | forall i:nat, le n i -> absLe (un i - l) (inject_Q (1#p)) }. +Instance seq_cv_morph + : forall (un : nat -> CReal), CMorphisms.Proper + (CMorphisms.respectful CRealEq CRelationClasses.iffT) (seq_cv un). +Proof. + split. intros. apply (seq_cv_proper un x). exact H0. exact H. + intros. apply (seq_cv_proper un y). exact H0. symmetry. exact H. +Qed. -Lemma Un_cv_mod_eq : forall (v u : nat -> CReal) (s : CReal), - (forall n:nat, u n == v n) - -> Un_cv_mod u s - -> Un_cv_mod v s. +Lemma growing_transit : forall un : nat -> CReal, + (forall n:nat, un n <= un (S n)) + -> forall n p : nat, le n p -> un n <= un p. Proof. - intros v u s seq H1 p. specialize (H1 p) as [N H0]. - exists N. intros. split. - rewrite <- seq. apply H0. apply H. - rewrite <- seq. apply H0. apply H. + induction p. + - intros. inversion H0. apply CRealLe_refl. + - intros. apply Nat.le_succ_r in H0. destruct H0. + apply (CReal_le_trans _ (un p)). apply IHp, H0. apply H. + subst n. apply CRealLe_refl. +Qed. + +Lemma growing_infinite : forall un : nat -> nat, + (forall n:nat, lt (un n) (un (S n))) + -> forall n : nat, le n (un n). +Proof. + induction n. + - apply le_0_n. + - specialize (H n). unfold lt in H. + apply (le_trans _ (S (un n))). apply le_n_S, IHn. exact H. +Qed. + +Lemma Un_cv_growing : forall (un : nat -> CReal) (l : CReal), + (forall n:nat, un n <= un (S n)) + -> (forall n:nat, un n <= l) + -> (forall p : positive, { n : nat | l - un n <= inject_Q (1#p) }) + -> seq_cv un l. +Proof. + intros. intro p. + specialize (H1 p) as [n nmaj]. exists n. + intros. rewrite CReal_abs_minus_sym, CReal_abs_right. + apply (CReal_le_trans _ (l - un n)). apply CReal_plus_le_compat_l. + apply CReal_opp_ge_le_contravar. + exact (growing_transit _ H n i H1). exact nmaj. + rewrite <- (CReal_plus_opp_r (un i)). apply CReal_plus_le_compat. + apply H0. apply CRealLe_refl. Qed. -Definition Un_cauchy_mod (un : nat -> CReal) : Set - := forall p : positive, - { n : nat | forall i j:nat, le n i -> le n j - -> absLe (un i - un j) (inject_Q (1#p)) }. (* Sharpen the archimedean property : constructive versions of @@ -142,11 +166,32 @@ Proof. reflexivity. Qed. +Lemma Qabs_Rabs : forall q : Q, + inject_Q (Qabs q) == CReal_abs (inject_Q q). +Proof. + intro q. apply Qabs_case. + - intros. rewrite CReal_abs_right. reflexivity. + apply inject_Q_le, H. + - intros. rewrite CReal_abs_left, opp_inject_Q. reflexivity. + apply inject_Q_le, H. +Qed. + Definition Un_cauchy_Q (xn : nat -> Q) : Set := forall n : positive, { k : nat | forall p q : nat, le k p -> le k q - -> Qle (-(1#n)) (xn p - xn q) - /\ Qle (xn p - xn q) (1#n) }. + -> (Qabs (xn p - xn q) <= 1#n)%Q }. + +Lemma CReal_smaller_interval : forall a b c d : CReal, + a <= c -> c <= b + -> a <= d -> d <= b + -> CReal_abs (d - c) <= b-a. +Proof. + intros. apply CReal_abs_le. split. + - apply (CReal_plus_le_reg_l (b+c)). ring_simplify. + apply CReal_plus_le_compat; assumption. + - apply (CReal_plus_le_reg_l (a+c)). ring_simplify. + apply CReal_plus_le_compat; assumption. +Qed. Lemma Rdiag_cauchy_sequence : forall (xn : nat -> CReal), Un_cauchy_mod xn @@ -154,92 +199,103 @@ Lemma Rdiag_cauchy_sequence : forall (xn : nat -> CReal), Proof. intros xn H p. specialize (H (2 * p)%positive) as [k cv]. exists (max k (2 * Pos.to_nat p)). intros. - specialize (cv p0 q). destruct cv. - apply (le_trans _ (Init.Nat.max k (2 * Pos.to_nat p))). - apply Nat.le_max_l. apply H. - apply (le_trans _ (Init.Nat.max k (2 * Pos.to_nat p))). - apply Nat.le_max_l. apply H0. - split. + specialize (cv p0 q + (le_trans _ _ _ (Nat.le_max_l _ _) H) + (le_trans _ _ _ (Nat.le_max_l _ _) H0)). + destruct (RQ_limit (xn p0) p0) as [r rmaj]. + destruct (RQ_limit (xn q) q) as [s smaj]. + apply Qabs_Qle_condition. split. - apply le_inject_Q. unfold Qminus. apply (CReal_le_trans _ (xn p0 - (xn q + inject_Q (1 # 2 * p)))). + unfold CReal_minus. rewrite CReal_opp_plus_distr. rewrite <- CReal_plus_assoc. - apply (CReal_plus_le_reg_r (inject_Q (1 # 2 * p))). - rewrite CReal_plus_assoc. rewrite CReal_plus_opp_l. rewrite CReal_plus_0_r. + apply (CReal_plus_le_reg_r (xn q - xn p0 - inject_Q (-(1#p)))). + ring_simplify. unfold CReal_minus. do 2 rewrite <- opp_inject_Q. rewrite <- inject_Q_plus. - setoid_replace (- (1 # p) + (1 # 2 * p))%Q with (- (1 # 2 * p))%Q. - rewrite opp_inject_Q. exact H1. - rewrite Qplus_comm. + setoid_replace (- - (1 # p) + - (1 # 2 * p))%Q with (1 # 2 * p)%Q. + rewrite CReal_abs_minus_sym in cv. + exact (CReal_le_trans _ _ _ (CReal_le_abs _ ) cv). + rewrite Qopp_involutive. setoid_replace (1#p)%Q with (2 # 2 *p)%Q. rewrite Qinv_minus_distr. reflexivity. reflexivity. + rewrite inject_Q_plus. apply CReal_plus_le_compat. apply CRealLt_asym. - destruct (RQ_limit (xn p0) p0); simpl. apply p1. + destruct (RQ_limit (xn p0) p0); simpl. apply rmaj. apply CRealLt_asym. - destruct (RQ_limit (xn q) q); unfold proj1_sig. rewrite opp_inject_Q. apply CReal_opp_gt_lt_contravar. - apply (CReal_lt_le_trans _ (xn q + inject_Q (1 # Pos.of_nat q))). - apply p1. apply CReal_plus_le_compat_l. apply inject_Q_le. + destruct smaj. apply (CReal_lt_le_trans _ _ _ c0). + apply CReal_plus_le_compat_l. apply inject_Q_le. apply Z2Nat.inj_le. discriminate. discriminate. simpl. assert ((Pos.to_nat p~0 <= q)%nat). { apply (le_trans _ (Init.Nat.max k (2 * Pos.to_nat p))). 2: apply H0. replace (p~0)%positive with (2*p)%positive. 2: reflexivity. rewrite Pos2Nat.inj_mul. apply Nat.le_max_r. } - rewrite Nat2Pos.id. apply H3. intro abs. subst q. - inversion H3. pose proof (Pos2Nat.is_pos (p~0)). - rewrite H5 in H4. inversion H4. + rewrite Nat2Pos.id. apply H1. intro abs. subst q. + inversion H1. pose proof (Pos2Nat.is_pos (p~0)). + rewrite H3 in H2. inversion H2. - apply le_inject_Q. unfold Qminus. apply (CReal_le_trans _ (xn p0 + inject_Q (1 # 2 * p) - xn q)). + rewrite inject_Q_plus. apply CReal_plus_le_compat. apply CRealLt_asym. destruct (RQ_limit (xn p0) p0); unfold proj1_sig. apply (CReal_lt_le_trans _ (xn p0 + inject_Q (1 # Pos.of_nat p0))). - apply p1. apply CReal_plus_le_compat_l. apply inject_Q_le. + apply rmaj. apply CReal_plus_le_compat_l. apply inject_Q_le. apply Z2Nat.inj_le. discriminate. discriminate. simpl. assert ((Pos.to_nat p~0 <= p0)%nat). { apply (le_trans _ (Init.Nat.max k (2 * Pos.to_nat p))). 2: apply H. replace (p~0)%positive with (2*p)%positive. 2: reflexivity. rewrite Pos2Nat.inj_mul. apply Nat.le_max_r. } - rewrite Nat2Pos.id. apply H3. intro abs. subst p0. - inversion H3. pose proof (Pos2Nat.is_pos (p~0)). - rewrite H5 in H4. inversion H4. + rewrite Nat2Pos.id. apply H1. intro abs. subst p0. + inversion H1. pose proof (Pos2Nat.is_pos (p~0)). + rewrite H3 in H2. inversion H2. apply CRealLt_asym. rewrite opp_inject_Q. apply CReal_opp_gt_lt_contravar. - destruct (RQ_limit (xn q) q); simpl. apply p1. + destruct (RQ_limit (xn q) q); simpl. apply smaj. + unfold CReal_minus. rewrite (CReal_plus_comm (xn p0)). rewrite CReal_plus_assoc. apply (CReal_plus_le_reg_l (- inject_Q (1 # 2 * p))). rewrite <- CReal_plus_assoc. rewrite CReal_plus_opp_l. rewrite CReal_plus_0_l. rewrite <- opp_inject_Q. rewrite <- inject_Q_plus. setoid_replace (- (1 # 2 * p) + (1 # p))%Q with (1 # 2 * p)%Q. - exact H2. rewrite Qplus_comm. + exact (CReal_le_trans _ _ _ (CReal_le_abs _) cv). + rewrite Qplus_comm. setoid_replace (1#p)%Q with (2 # 2*p)%Q. rewrite Qinv_minus_distr. reflexivity. reflexivity. Qed. -Lemma doubleLeCovariant : forall a b c d e f : CReal, - a == b -> c == d -> e == f - -> (a <= c <= e) - -> (b <= d <= f). +Lemma CReal_absSmall : forall (x y : CReal) (n : positive), + (Qlt (2 # n) + (proj1_sig x (Pos.to_nat n) - Qabs (proj1_sig y (Pos.to_nat n)))) + -> CReal_abs y <= x. Proof. - split. rewrite <- H. rewrite <- H0. apply H2. - rewrite <- H0. rewrite <- H1. apply H2. + intros x y n maj. apply CReal_abs_le. split. + - apply CRealLt_asym. exists n. destruct x as [xn caux], y as [yn cauy]; simpl. + simpl in maj. unfold Qminus. rewrite Qopp_involutive. + rewrite Qplus_comm. + apply (Qlt_le_trans _ (xn (Pos.to_nat n) - Qabs (yn (Pos.to_nat n)))). + apply maj. apply Qplus_le_r. + rewrite <- (Qopp_involutive (yn (Pos.to_nat n))). + apply Qopp_le_compat. rewrite Qabs_opp. apply Qle_Qabs. + - apply CRealLt_asym. exists n. destruct x as [xn caux], y as [yn cauy]; simpl. + simpl in maj. + apply (Qlt_le_trans _ (xn (Pos.to_nat n) - Qabs (yn (Pos.to_nat n)))). + apply maj. apply Qplus_le_r. apply Qopp_le_compat. apply Qle_Qabs. Qed. + (* An element of CReal is a Cauchy sequence of rational numbers, show that it converges to itself in CReal. *) Lemma CReal_cv_self : forall (qn : nat -> Q) (x : CReal) (cvmod : positive -> nat), QSeqEquiv qn (fun n => proj1_sig x n) cvmod - -> Un_cv_mod (fun n => inject_Q (qn n)) x. + -> seq_cv (fun n => inject_Q (qn n)) x. Proof. intros qn x cvmod H p. specialize (H (2*p)%positive). exists (cvmod (2*p)%positive). - intros p0 H0. unfold absLe, CReal_minus. - apply (doubleLeCovariant (-inject_Q (1#p)) _ (inject_Q (qn p0) - x) _ (inject_Q (1#p))). - reflexivity. reflexivity. reflexivity. - apply (CReal_absSmall _ _ (Pos.max (4 * p)%positive (Pos.of_nat (cvmod (2 * p)%positive)))). + intros p0 H0. + apply (CReal_absSmall + _ _ (Pos.max (4 * p)%positive (Pos.of_nat (cvmod (2 * p)%positive)))). setoid_replace (proj1_sig (inject_Q (1 # p)) (Pos.to_nat (Pos.max (4 * p) (Pos.of_nat (cvmod (2 * p)%positive))))) with (1 # p)%Q. 2: reflexivity. @@ -266,22 +322,12 @@ Proof. reflexivity. reflexivity. Qed. -Lemma Un_cv_extens : forall (xn yn : nat -> CReal) (l : CReal), - Un_cv_mod xn l - -> (forall n : nat, xn n == yn n) - -> Un_cv_mod yn l. -Proof. - intros. intro p. destruct (H p) as [n cv]. exists n. - intros. unfold absLe, CReal_minus. - split; rewrite <- (H0 i); apply cv; apply H1. -Qed. - (* Q is dense in Archimedean fields, so all real numbers are limits of rational sequences. The biggest computable such field has all rational limits. *) Lemma R_has_all_rational_limits : forall qn : nat -> Q, Un_cauchy_Q qn - -> { r : CReal & Un_cv_mod (fun n:nat => inject_Q (qn n)) r }. + -> { r : CReal & seq_cv (fun n:nat => inject_Q (qn n)) r }. Proof. (* qn is an element of CReal. Show that inject_Q qn converges to it in CReal. *) @@ -289,8 +335,7 @@ Proof. destruct (standard_modulus qn (fun p => proj1_sig (H (Pos.succ p)))). - intros p n k H0 H1. destruct (H (Pos.succ p)%positive) as [x a]; simpl in H0,H1. specialize (a n k H0 H1). - apply (Qle_lt_trans _ (1#Pos.succ p)). - apply Qabs_Qle_condition. exact a. + apply (Qle_lt_trans _ (1#Pos.succ p) _ a). apply Pos2Z.pos_lt_pos. simpl. apply Pos.lt_succ_diag_r. - exists (exist _ (fun n : nat => qn (increasing_modulus (fun p : positive => proj1_sig (H (Pos.succ p))) n)) H0). @@ -302,24 +347,25 @@ Qed. Lemma Rcauchy_complete : forall (xn : nat -> CReal), Un_cauchy_mod xn - -> { l : CReal & Un_cv_mod xn l }. + -> { l : CReal & seq_cv xn l }. Proof. intros xn cau. destruct (R_has_all_rational_limits (fun n => let (l,_) := RQ_limit (xn n) n in l) (Rdiag_cauchy_sequence xn cau)) as [l cv]. exists l. intro p. specialize (cv (2*p)%positive) as [k cv]. - exists (max k (2 * Pos.to_nat p)). intros p0 H. specialize (cv p0). - destruct cv as [H0 H1]. apply (le_trans _ (max k (2 * Pos.to_nat p))). - apply Nat.le_max_l. apply H. - destruct (RQ_limit (xn p0) p0) as [q maj]; unfold proj1_sig in H0,H1. - split. + exists (max k (2 * Pos.to_nat p)). intros p0 H. + specialize (cv p0 (le_trans _ _ _ (Nat.le_max_l _ _) H)). + destruct (RQ_limit (xn p0) p0) as [q maj]. + apply CReal_abs_le. split. - apply (CReal_le_trans _ (inject_Q q - inject_Q (1 # 2 * p) - l)). + unfold CReal_minus. rewrite (CReal_plus_comm (inject_Q q)). - apply (CReal_plus_le_reg_l (inject_Q (1 # 2 * p))). - ring_simplify. unfold CReal_minus. rewrite <- opp_inject_Q. rewrite <- inject_Q_plus. - setoid_replace ((1 # 2 * p) + - (1 # p))%Q with (-(1#2*p))%Q. - rewrite opp_inject_Q. apply H0. + apply (CReal_plus_le_reg_r (inject_Q (1 # p) + l - inject_Q q)). + ring_simplify. unfold CReal_minus. + rewrite <- (opp_inject_Q (1# 2*p)), <- inject_Q_plus. + setoid_replace ((1 # p) + - (1 # 2* p))%Q with (1#2*p)%Q. + rewrite CReal_abs_minus_sym in cv. + exact (CReal_le_trans _ _ _ (CReal_le_abs _) cv). setoid_replace (1#p)%Q with (2 # 2*p)%Q. rewrite Qinv_minus_distr. reflexivity. reflexivity. + unfold CReal_minus. @@ -335,48 +381,66 @@ Proof. 2: apply H. replace (p~0)%positive with (2*p)%positive. 2: reflexivity. rewrite Pos2Nat.inj_mul. apply Nat.le_max_r. } - rewrite Nat2Pos.id. apply H2. intro abs. subst p0. - inversion H2. pose proof (Pos2Nat.is_pos (p~0)). - rewrite H4 in H3. inversion H3. + rewrite Nat2Pos.id. apply H0. intro abs. subst p0. + inversion H0. pose proof (Pos2Nat.is_pos (p~0)). + rewrite H2 in H1. inversion H1. - apply (CReal_le_trans _ (inject_Q q - l)). + unfold CReal_minus. do 2 rewrite <- (CReal_plus_comm (-l)). apply CReal_plus_le_compat_l. apply CRealLt_asym, maj. + apply (CReal_le_trans _ (inject_Q (1 # 2 * p))). - apply H1. apply inject_Q_le. - rewrite <- Qplus_0_r. + exact (CReal_le_trans _ _ _ (CReal_le_abs _) cv). + apply inject_Q_le. rewrite <- Qplus_0_r. setoid_replace (1#p)%Q with ((1#2*p)+(1#2*p))%Q. apply Qplus_le_r. discriminate. rewrite Qinv_plus_distr. reflexivity. Qed. -Definition CRealImplem : ConstructiveReals. +Lemma CRealLtIsLinear : isLinearOrder CRealLt. Proof. - assert (isLinearOrder CReal CRealLt) as lin. - { repeat split. exact CRealLt_asym. - exact CReal_lt_trans. - intros. destruct (CRealLt_dec x z y H). - left. exact c. right. exact c. } - apply (Build_ConstructiveReals - CReal CRealLt lin CRealLtProp - CRealLtEpsilon CRealLtForget CRealLtDisjunctEpsilon - (inject_Q 0) (inject_Q 1) - CReal_plus CReal_opp CReal_mult - CReal_isRing CReal_isRingExt CRealLt_0_1 - CReal_plus_lt_compat_l CReal_plus_lt_reg_l - CReal_mult_lt_0_compat - CReal_inv CReal_inv_l CReal_inv_0_lt_compat - inject_Q inject_Q_plus inject_Q_mult - inject_Q_one inject_Q_lt lt_inject_Q - CRealQ_dense Rup_pos). - - intros. destruct (Rcauchy_complete xn) as [l cv]. - intro n. destruct (H n). exists x. intros. - specialize (a i j H0 H1) as [a b]. split. 2: exact b. - rewrite <- opp_inject_Q. - setoid_replace (-(1#n))%Q with (-1#n)%Q. exact a. reflexivity. - exists l. intros p. destruct (cv p). - exists x. intros. specialize (a i H0). split. 2: apply a. - unfold orderLe. - intro abs. setoid_replace (-1#p)%Q with (-(1#p))%Q in abs. - rewrite opp_inject_Q in abs. destruct a. contradiction. - reflexivity. + repeat split. exact CRealLt_asym. + exact CReal_lt_trans. + intros. destruct (CRealLt_dec x z y H). + left. exact c. right. exact c. +Qed. + +Lemma CRealAbsLUB : forall x y : CReal, + x <= y /\ (- x) <= y <-> (CReal_abs x) <= y. +Proof. + split. + - intros [H H0]. apply CReal_abs_le. split. 2: exact H. + apply (CReal_plus_le_reg_r (y-x)). ring_simplify. exact H0. + - intros. apply CReal_abs_def2 in H. destruct H. split. + exact H. fold (-x <= y). + apply (CReal_plus_le_reg_r (x-y)). ring_simplify. exact H0. +Qed. + +Lemma CRealComplete : forall xn : nat -> CReal, + (forall p : positive, + {n : nat | + forall i j : nat, + (n <= i)%nat -> (n <= j)%nat -> (CReal_abs (xn i + - xn j)) <= (inject_Q (1 # p))}) -> + {l : CReal & + forall p : positive, + {n : nat | + forall i : nat, (n <= i)%nat -> (CReal_abs (xn i + - l)) <= (inject_Q (1 # p))}}. +Proof. + intros. destruct (Rcauchy_complete xn) as [l cv]. + intro p. destruct (H p) as [n a]. exists n. intros. + exact (a i j H0 H1). + exists l. intros p. destruct (cv p). + exists x. exact c. Defined. + +Definition CRealConstructive : ConstructiveReals + := Build_ConstructiveReals + CReal CRealLt CRealLtIsLinear CRealLtProp + CRealLtEpsilon CRealLtForget CRealLtDisjunctEpsilon + (inject_Q 0) (inject_Q 1) + CReal_plus CReal_opp CReal_mult + CReal_isRing CReal_isRingExt CRealLt_0_1 + CReal_plus_lt_compat_l CReal_plus_lt_reg_l + CReal_mult_lt_0_compat + CReal_inv CReal_inv_l CReal_inv_0_lt_compat + inject_Q inject_Q_plus inject_Q_mult + inject_Q_one inject_Q_lt lt_inject_Q + CRealQ_dense Rup_pos CReal_abs CRealAbsLUB CRealComplete. diff --git a/theories/Reals/ConstructiveReals.v b/theories/Reals/ConstructiveReals.v deleted file mode 100644 index d6eee518d3..0000000000 --- a/theories/Reals/ConstructiveReals.v +++ /dev/null @@ -1,835 +0,0 @@ -(************************************************************************) -(* * The Coq Proof Assistant / The Coq Development Team *) -(* v * Copyright INRIA, CNRS and contributors *) -(* <O___,, * (see version control and CREDITS file for authors & dates) *) -(* \VV/ **************************************************************) -(* // * This file is distributed under the terms of the *) -(* * GNU Lesser General Public License Version 2.1 *) -(* * (see LICENSE file for the text of the license) *) -(************************************************************************) -(************************************************************************) - -(** An interface for constructive and computable real numbers. - All of its instances are isomorphic (see file ConstructiveRealsMorphisms). - For example it contains the Cauchy reals implemented in file - ConstructivecauchyReals and the sumbool-based Dedekind reals defined by - -Structure R := { - (* The cuts are represented as propositional functions, rather than subsets, - as there are no subsets in type theory. *) - lower : Q -> Prop; - upper : Q -> Prop; - (* The cuts respect equality on Q. *) - lower_proper : Proper (Qeq ==> iff) lower; - upper_proper : Proper (Qeq ==> iff) upper; - (* The cuts are inhabited. *) - lower_bound : { q : Q | lower q }; - upper_bound : { r : Q | upper r }; - (* The lower cut is a lower set. *) - lower_lower : forall q r, q < r -> lower r -> lower q; - (* The lower cut is open. *) - lower_open : forall q, lower q -> exists r, q < r /\ lower r; - (* The upper cut is an upper set. *) - upper_upper : forall q r, q < r -> upper q -> upper r; - (* The upper cut is open. *) - upper_open : forall r, upper r -> exists q, q < r /\ upper q; - (* The cuts are disjoint. *) - disjoint : forall q, ~ (lower q /\ upper q); - (* There is no gap between the cuts. *) - located : forall q r, q < r -> { lower q } + { upper r } -}. - - see github.com/andrejbauer/dedekind-reals for the Prop-based - version of those Dedekind reals (although Prop fails to make - them an instance of ConstructiveReals). - - Any computation about constructive reals, can be worked - in the fastest instance for it; we then transport the results - to all other instances by the isomorphisms. This way of working - is different from the usual interfaces, where we would rather - prove things abstractly, by quantifying universally on the instance. - - The functions of ConstructiveReals do not have a direct impact - on performance, because algorithms will be extracted from instances, - and because fast ConstructiveReals morphisms should be coded - manually. However, since instances are forced to implement - those functions, it is probable that they will also use them - in their algorithms. So those functions hint at what we think - will yield fast and small extracted programs. *) - - -Require Import QArith. - -Definition isLinearOrder (X : Set) (Xlt : X -> X -> Set) : Set - := (forall x y:X, Xlt x y -> Xlt y x -> False) - * (forall x y z : X, Xlt x y -> Xlt y z -> Xlt x z) - * (forall x y z : X, Xlt x z -> Xlt x y + Xlt y z). - -Definition orderEq (X : Set) (Xlt : X -> X -> Set) (x y : X) : Prop - := (Xlt x y -> False) /\ (Xlt y x -> False). - -Definition orderAppart (X : Set) (Xlt : X -> X -> Set) (x y : X) : Set - := Xlt x y + Xlt y x. - -Definition orderLe (X : Set) (Xlt : X -> X -> Set) (x y : X) : Prop - := Xlt y x -> False. - -Definition sig_forall_dec_T : Type - := forall (P : nat -> Prop), (forall n, {P n} + {~P n}) - -> {n | ~P n} + {forall n, P n}. - -Definition sig_not_dec_T : Type := forall P : Prop, { ~~P } + { ~P }. - -Record ConstructiveReals : Type := - { - CRcarrier : Set; - - (* Put this order relation in sort Set rather than Prop, - to allow the definition of fast ConstructiveReals morphisms. - For example, the Cauchy reals do store information in - the proofs of CRlt, which is used in algorithms in sort Set. *) - CRlt : CRcarrier -> CRcarrier -> Set; - CRltLinear : isLinearOrder CRcarrier CRlt; - - (* The propositional truncation of CRlt. It facilitates proofs - when computations are not considered important, for example in - classical reals with extra logical axioms. *) - CRltProp : CRcarrier -> CRcarrier -> Prop; - (* This choice algorithm can be slow, keep it for the classical - quotient of the reals, where computations are blocked by - axioms like LPO. *) - CRltEpsilon : forall x y : CRcarrier, CRltProp x y -> CRlt x y; - CRltForget : forall x y : CRcarrier, CRlt x y -> CRltProp x y; - CRltDisjunctEpsilon : forall a b c d : CRcarrier, - (CRltProp a b \/ CRltProp c d) -> CRlt a b + CRlt c d; - - (* Constants *) - CRzero : CRcarrier; - CRone : CRcarrier; - - (* Addition and multiplication *) - CRplus : CRcarrier -> CRcarrier -> CRcarrier; - CRopp : CRcarrier -> CRcarrier; (* Computable opposite, - stronger than Prop-existence of opposite *) - CRmult : CRcarrier -> CRcarrier -> CRcarrier; - - CRisRing : ring_theory CRzero CRone CRplus CRmult - (fun x y => CRplus x (CRopp y)) CRopp (orderEq CRcarrier CRlt); - CRisRingExt : ring_eq_ext CRplus CRmult CRopp (orderEq CRcarrier CRlt); - - (* Compatibility with order *) - CRzero_lt_one : CRlt CRzero CRone; (* 0 # 1 would only allow 0 < 1 because - of Fmult_lt_0_compat so request 0 < 1 directly. *) - CRplus_lt_compat_l : forall r r1 r2 : CRcarrier, - CRlt r1 r2 -> CRlt (CRplus r r1) (CRplus r r2); - CRplus_lt_reg_l : forall r r1 r2 : CRcarrier, - CRlt (CRplus r r1) (CRplus r r2) -> CRlt r1 r2; - CRmult_lt_0_compat : forall x y : CRcarrier, - CRlt CRzero x -> CRlt CRzero y -> CRlt CRzero (CRmult x y); - - (* A constructive total inverse function on F would need to be continuous, - which is impossible because we cannot connect plus and minus infinities. - Therefore it has to be a partial function, defined on non zero elements. - For this reason we cannot use Coq's field_theory and field tactic. - - To implement Finv by Cauchy sequences we need orderAppart, - ~orderEq is not enough. *) - CRinv : forall x : CRcarrier, orderAppart _ CRlt x CRzero -> CRcarrier; - CRinv_l : forall (r:CRcarrier) (rnz : orderAppart _ CRlt r CRzero), - orderEq _ CRlt (CRmult (CRinv r rnz) r) CRone; - CRinv_0_lt_compat : forall (r : CRcarrier) (rnz : orderAppart _ CRlt r CRzero), - CRlt CRzero r -> CRlt CRzero (CRinv r rnz); - - (* The initial field morphism (in characteristic zero). - The abstract definition by iteration of addition is - probably the slowest. Let each instance implement - a faster (and often simpler) version. *) - CR_of_Q : Q -> CRcarrier; - CR_of_Q_plus : forall q r : Q, orderEq _ CRlt (CR_of_Q (q+r)) - (CRplus (CR_of_Q q) (CR_of_Q r)); - CR_of_Q_mult : forall q r : Q, orderEq _ CRlt (CR_of_Q (q*r)) - (CRmult (CR_of_Q q) (CR_of_Q r)); - CR_of_Q_one : orderEq _ CRlt (CR_of_Q 1) CRone; - CR_of_Q_lt : forall q r : Q, - Qlt q r -> CRlt (CR_of_Q q) (CR_of_Q r); - lt_CR_of_Q : forall q r : Q, - CRlt (CR_of_Q q) (CR_of_Q r) -> Qlt q r; - - (* This function is very fast in both the Cauchy and Dedekind - instances, because this rational number q is almost what - the proof of CRlt x y contains. - This function is also the heart of the computation of - constructive real numbers : it approximates x to any - requested precision y. *) - CR_Q_dense : forall x y : CRcarrier, CRlt x y -> - { q : Q & prod (CRlt x (CR_of_Q q)) - (CRlt (CR_of_Q q) y) }; - CR_archimedean : forall x : CRcarrier, - { n : positive & CRlt x (CR_of_Q (Z.pos n # 1)) }; - - CRminus (x y : CRcarrier) : CRcarrier - := CRplus x (CRopp y); - - (* Definitions of convergence and Cauchy-ness. The formulas - with orderLe or CRlt are logically equivalent, the choice of - orderLe in sort Prop is a question of performance. - It is very rare to turn back to the strict order to - define functions in sort Set, so we prefer to discard - those proofs during extraction. And even in those rare cases, - it is easy to divide epsilon by 2 for example. *) - CR_cv (un : nat -> CRcarrier) (l : CRcarrier) : Set - := forall p:positive, - { n : nat | forall i:nat, le n i - -> orderLe _ CRlt (CR_of_Q (-1#p)) (CRminus (un i) l) - /\ orderLe _ CRlt (CRminus (un i) l) (CR_of_Q (1#p)) }; - CR_cauchy (un : nat -> CRcarrier) : Set - := forall p : positive, - { n : nat | forall i j:nat, le n i -> le n j - -> orderLe _ CRlt (CR_of_Q (-1#p)) (CRminus (un i) (un j)) - /\ orderLe _ CRlt (CRminus (un i) (un j)) (CR_of_Q (1#p)) }; - - (* For the Cauchy reals, this algorithm consists in building - a Cauchy sequence of rationals un : nat -> Q that has - the same limit as xn. For each n:nat, un n is a 1/n - rational approximation of a point of xn that has converged - within 1/n. *) - CR_complete : - forall xn : (nat -> CRcarrier), - CR_cauchy xn -> { l : CRcarrier & CR_cv xn l }; - }. - -Lemma CRlt_asym : forall (R : ConstructiveReals) (x y : CRcarrier R), - CRlt R x y -> CRlt R y x -> False. -Proof. - intros. destruct (CRltLinear R), p. - apply (f x y); assumption. -Qed. - -Lemma CRlt_proper - : forall R : ConstructiveReals, - CMorphisms.Proper - (CMorphisms.respectful (orderEq _ (CRlt R)) - (CMorphisms.respectful (orderEq _ (CRlt R)) CRelationClasses.iffT)) (CRlt R). -Proof. - intros R x y H x0 y0 H0. destruct H, H0. - destruct (CRltLinear R). split. - - intro. destruct (s x y x0). assumption. - contradiction. destruct (s y y0 x0). - assumption. assumption. contradiction. - - intro. destruct (s y x y0). assumption. - contradiction. destruct (s x x0 y0). - assumption. assumption. contradiction. -Qed. - -Lemma CRle_refl : forall (R : ConstructiveReals) (x : CRcarrier R), - CRlt R x x -> False. -Proof. - intros. destruct (CRltLinear R), p. - exact (f x x H H). -Qed. - -Lemma CRle_lt_trans : forall (R : ConstructiveReals) (r1 r2 r3 : CRcarrier R), - (CRlt R r2 r1 -> False) -> CRlt R r2 r3 -> CRlt R r1 r3. -Proof. - intros. destruct (CRltLinear R). - destruct (s r2 r1 r3 H0). contradiction. apply c. -Qed. - -Lemma CRlt_le_trans : forall (R : ConstructiveReals) (r1 r2 r3 : CRcarrier R), - CRlt R r1 r2 -> (CRlt R r3 r2 -> False) -> CRlt R r1 r3. -Proof. - intros. destruct (CRltLinear R). - destruct (s r1 r3 r2 H). apply c. contradiction. -Qed. - -Lemma CRle_trans : forall (R : ConstructiveReals) (x y z : CRcarrier R), - orderLe _ (CRlt R) x y -> orderLe _ (CRlt R) y z -> orderLe _ (CRlt R) x z. -Proof. - intros. intro abs. apply H0. - apply (CRlt_le_trans _ _ x); assumption. -Qed. - -Lemma CRlt_trans : forall (R : ConstructiveReals) (x y z : CRcarrier R), - CRlt R x y -> CRlt R y z -> CRlt R x z. -Proof. - intros. apply (CRlt_le_trans R _ y _ H). - apply CRlt_asym. exact H0. -Defined. - -Lemma CRlt_trans_flip : forall (R : ConstructiveReals) (x y z : CRcarrier R), - CRlt R y z -> CRlt R x y -> CRlt R x z. -Proof. - intros. apply (CRlt_le_trans R _ y). exact H0. - apply CRlt_asym. exact H. -Defined. - -Lemma CReq_refl : forall (R : ConstructiveReals) (x : CRcarrier R), - orderEq _ (CRlt R) x x. -Proof. - split; apply CRle_refl. -Qed. - -Lemma CReq_sym : forall (R : ConstructiveReals) (x y : CRcarrier R), - orderEq _ (CRlt R) x y - -> orderEq _ (CRlt R) y x. -Proof. - intros. destruct H. split; intro abs; contradiction. -Qed. - -Lemma CReq_trans : forall (R : ConstructiveReals) (x y z : CRcarrier R), - orderEq _ (CRlt R) x y - -> orderEq _ (CRlt R) y z - -> orderEq _ (CRlt R) x z. -Proof. - intros. destruct H,H0. destruct (CRltLinear R), p. split. - - intro abs. destruct (s _ y _ abs); contradiction. - - intro abs. destruct (s _ y _ abs); contradiction. -Qed. - -Lemma CR_setoid : forall R : ConstructiveReals, - Setoid_Theory (CRcarrier R) (orderEq _ (CRlt R)). -Proof. - split. intro x. apply CReq_refl. - intros x y. apply CReq_sym. - intros x y z. apply CReq_trans. -Qed. - -Lemma CRplus_0_r : forall (R : ConstructiveReals) (x : CRcarrier R), - orderEq _ (CRlt R) (CRplus R x (CRzero R)) x. -Proof. - intros. destruct (CRisRing R). - apply (CReq_trans R _ (CRplus R (CRzero R) x)). - apply Radd_comm. apply Radd_0_l. -Qed. - -Lemma CRmult_1_r : forall (R : ConstructiveReals) (x : CRcarrier R), - orderEq _ (CRlt R) (CRmult R x (CRone R)) x. -Proof. - intros. destruct (CRisRing R). - apply (CReq_trans R _ (CRmult R (CRone R) x)). - apply Rmul_comm. apply Rmul_1_l. -Qed. - -Lemma CRplus_opp_l : forall (R : ConstructiveReals) (x : CRcarrier R), - orderEq _ (CRlt R) (CRplus R (CRopp R x) x) (CRzero R). -Proof. - intros. destruct (CRisRing R). - apply (CReq_trans R _ (CRplus R x (CRopp R x))). - apply Radd_comm. apply Ropp_def. -Qed. - -Lemma CRplus_lt_compat_r : forall (R : ConstructiveReals) (r r1 r2 : CRcarrier R), - CRlt R r1 r2 -> CRlt R (CRplus R r1 r) (CRplus R r2 r). -Proof. - intros. destruct (CRisRing R). - apply (CRlt_proper R (CRplus R r r1) (CRplus R r1 r) (Radd_comm _ _) - (CRplus R r2 r) (CRplus R r2 r)). - apply CReq_refl. - apply (CRlt_proper R _ _ (CReq_refl _ _) _ (CRplus R r r2)). - apply Radd_comm. apply CRplus_lt_compat_l. exact H. -Qed. - -Lemma CRplus_lt_reg_r : forall (R : ConstructiveReals) (r r1 r2 : CRcarrier R), - CRlt R (CRplus R r1 r) (CRplus R r2 r) -> CRlt R r1 r2. -Proof. - intros. destruct (CRisRing R). - apply (CRlt_proper R (CRplus R r r1) (CRplus R r1 r) (Radd_comm _ _) - (CRplus R r2 r) (CRplus R r2 r)) in H. - 2: apply CReq_refl. - apply (CRlt_proper R _ _ (CReq_refl _ _) _ (CRplus R r r2)) in H. - apply CRplus_lt_reg_l in H. exact H. - apply Radd_comm. -Qed. - -Lemma CRplus_le_compat_l : forall (R : ConstructiveReals) (r r1 r2 : CRcarrier R), - orderLe _ (CRlt R) r1 r2 - -> orderLe _ (CRlt R) (CRplus R r r1) (CRplus R r r2). -Proof. - intros. intros abs. apply CRplus_lt_reg_l in abs. apply H. exact abs. -Qed. - -Lemma CRplus_le_compat_r : forall (R : ConstructiveReals) (r r1 r2 : CRcarrier R), - orderLe _ (CRlt R) r1 r2 - -> orderLe _ (CRlt R) (CRplus R r1 r) (CRplus R r2 r). -Proof. - intros. intros abs. apply CRplus_lt_reg_r in abs. apply H. exact abs. -Qed. - -Lemma CRplus_le_reg_l : forall (R : ConstructiveReals) (r r1 r2 : CRcarrier R), - orderLe _ (CRlt R) (CRplus R r r1) (CRplus R r r2) - -> orderLe _ (CRlt R) r1 r2. -Proof. - intros. intro abs. apply H. clear H. - apply CRplus_lt_compat_l. exact abs. -Qed. - -Lemma CRplus_le_reg_r : forall (R : ConstructiveReals) (r r1 r2 : CRcarrier R), - orderLe _ (CRlt R) (CRplus R r1 r) (CRplus R r2 r) - -> orderLe _ (CRlt R) r1 r2. -Proof. - intros. intro abs. apply H. clear H. - apply CRplus_lt_compat_r. exact abs. -Qed. - -Lemma CRplus_lt_le_compat : - forall (R : ConstructiveReals) (r1 r2 r3 r4 : CRcarrier R), - CRlt R r1 r2 - -> (CRlt R r4 r3 -> False) - -> CRlt R (CRplus R r1 r3) (CRplus R r2 r4). -Proof. - intros. apply (CRlt_le_trans R _ (CRplus R r2 r3)). - apply CRplus_lt_compat_r. exact H. intro abs. - apply CRplus_lt_reg_l in abs. contradiction. -Qed. - -Lemma CRplus_eq_reg_l : forall (R : ConstructiveReals) (r r1 r2 : CRcarrier R), - orderEq _ (CRlt R) (CRplus R r r1) (CRplus R r r2) - -> orderEq _ (CRlt R) r1 r2. -Proof. - intros. - destruct (CRisRingExt R). clear Rmul_ext Ropp_ext. - pose proof (Radd_ext - (CRopp R r) (CRopp R r) (CReq_refl _ _) - _ _ H). - destruct (CRisRing R). - apply (CReq_trans _ r1) in H0. - apply (CReq_trans R _ _ _ H0). - apply (CReq_trans R _ (CRplus R (CRplus R (CRopp R r) r) r2)). - apply Radd_assoc. - apply (CReq_trans R _ (CRplus R (CRzero R) r2)). - apply Radd_ext. apply CRplus_opp_l. apply CReq_refl. - apply Radd_0_l. apply CReq_sym. - apply (CReq_trans R _ (CRplus R (CRplus R (CRopp R r) r) r1)). - apply Radd_assoc. - apply (CReq_trans R _ (CRplus R (CRzero R) r1)). - apply Radd_ext. apply CRplus_opp_l. apply CReq_refl. - apply Radd_0_l. -Qed. - -Lemma CRplus_eq_reg_r : forall (R : ConstructiveReals) (r r1 r2 : CRcarrier R), - orderEq _ (CRlt R) (CRplus R r1 r) (CRplus R r2 r) - -> orderEq _ (CRlt R) r1 r2. -Proof. - intros. apply (CRplus_eq_reg_l R r). - apply (CReq_trans R _ (CRplus R r1 r)). apply (Radd_comm (CRisRing R)). - apply (CReq_trans R _ (CRplus R r2 r)). - exact H. apply (Radd_comm (CRisRing R)). -Qed. - -Lemma CRopp_involutive : forall (R : ConstructiveReals) (r : CRcarrier R), - orderEq _ (CRlt R) (CRopp R (CRopp R r)) r. -Proof. - intros. apply (CRplus_eq_reg_l R (CRopp R r)). - apply (CReq_trans R _ (CRzero R)). apply CRisRing. - apply CReq_sym, (CReq_trans R _ (CRplus R r (CRopp R r))). - apply CRisRing. apply CRisRing. -Qed. - -Lemma CRopp_gt_lt_contravar - : forall (R : ConstructiveReals) (r1 r2 : CRcarrier R), - CRlt R r2 r1 -> CRlt R (CRopp R r1) (CRopp R r2). -Proof. - intros. apply (CRplus_lt_reg_l R r1). - destruct (CRisRing R). - apply (CRle_lt_trans R _ (CRzero R)). apply Ropp_def. - apply (CRplus_lt_compat_l R (CRopp R r2)) in H. - apply (CRle_lt_trans R _ (CRplus R (CRopp R r2) r2)). - apply (CRle_trans R _ (CRplus R r2 (CRopp R r2))). - destruct (Ropp_def r2). exact H0. - destruct (Radd_comm r2 (CRopp R r2)). exact H1. - apply (CRlt_le_trans R _ _ _ H). - destruct (Radd_comm r1 (CRopp R r2)). exact H0. -Qed. - -Lemma CRopp_lt_cancel : forall (R : ConstructiveReals) (r1 r2 : CRcarrier R), - CRlt R (CRopp R r2) (CRopp R r1) -> CRlt R r1 r2. -Proof. - intros. apply (CRplus_lt_compat_r R r1) in H. - destruct (CRplus_opp_l R r1) as [_ H1]. - apply (CRlt_le_trans R _ _ _ H) in H1. clear H. - apply (CRplus_lt_compat_l R r2) in H1. - destruct (CRplus_0_r R r2) as [_ H0]. - apply (CRlt_le_trans R _ _ _ H1) in H0. clear H1. - destruct (Radd_assoc (CRisRing R) r2 (CRopp R r2) r1) as [H _]. - apply (CRle_lt_trans R _ _ _ H) in H0. clear H. - apply (CRle_lt_trans R _ (CRplus R (CRzero R) r1)). - apply (Radd_0_l (CRisRing R)). - apply (CRle_lt_trans R _ (CRplus R (CRplus R r2 (CRopp R r2)) r1)). - 2: exact H0. apply CRplus_le_compat_r. - destruct (Ropp_def (CRisRing R) r2). exact H. -Qed. - -Lemma CRopp_plus_distr : forall (R : ConstructiveReals) (r1 r2 : CRcarrier R), - orderEq _ (CRlt R) (CRopp R (CRplus R r1 r2)) (CRplus R (CRopp R r1) (CRopp R r2)). -Proof. - intros. destruct (CRisRing R), (CRisRingExt R). - apply (CRplus_eq_reg_l R (CRplus R r1 r2)). - apply (CReq_trans R _ (CRzero R)). apply Ropp_def. - apply (CReq_trans R _ (CRplus R (CRplus R r2 r1) (CRplus R (CRopp R r1) (CRopp R r2)))). - apply (CReq_trans R _ (CRplus R r2 (CRplus R r1 (CRplus R (CRopp R r1) (CRopp R r2))))). - apply (CReq_trans R _ (CRplus R r2 (CRopp R r2))). - apply CReq_sym. apply Ropp_def. apply Radd_ext. - apply CReq_refl. - apply (CReq_trans R _ (CRplus R (CRzero R) (CRopp R r2))). - apply CReq_sym, Radd_0_l. - apply (CReq_trans R _ (CRplus R (CRplus R r1 (CRopp R r1)) (CRopp R r2))). - apply Radd_ext. 2: apply CReq_refl. apply CReq_sym, Ropp_def. - apply CReq_sym, Radd_assoc. apply Radd_assoc. - apply Radd_ext. 2: apply CReq_refl. apply Radd_comm. -Qed. - -Lemma CRmult_plus_distr_l : forall (R : ConstructiveReals) (r1 r2 r3 : CRcarrier R), - orderEq _ (CRlt R) (CRmult R r1 (CRplus R r2 r3)) - (CRplus R (CRmult R r1 r2) (CRmult R r1 r3)). -Proof. - intros. destruct (CRisRing R). - apply (CReq_trans R _ (CRmult R (CRplus R r2 r3) r1)). - apply Rmul_comm. - apply (CReq_trans R _ (CRplus R (CRmult R r2 r1) (CRmult R r3 r1))). - apply Rdistr_l. - apply (CReq_trans R _ (CRplus R (CRmult R r1 r2) (CRmult R r3 r1))). - destruct (CRisRingExt R). apply Radd_ext. - apply Rmul_comm. apply CReq_refl. - destruct (CRisRingExt R). apply Radd_ext. - apply CReq_refl. apply Rmul_comm. -Qed. - -(* x == x+x -> x == 0 *) -Lemma CRzero_double : forall (R : ConstructiveReals) (x : CRcarrier R), - orderEq _ (CRlt R) x (CRplus R x x) - -> orderEq _ (CRlt R) x (CRzero R). -Proof. - intros. - apply (CRplus_eq_reg_l R x), CReq_sym, (CReq_trans R _ x). - apply CRplus_0_r. exact H. -Qed. - -Lemma CRmult_0_r : forall (R : ConstructiveReals) (x : CRcarrier R), - orderEq _ (CRlt R) (CRmult R x (CRzero R)) (CRzero R). -Proof. - intros. apply CRzero_double. - apply (CReq_trans R _ (CRmult R x (CRplus R (CRzero R) (CRzero R)))). - destruct (CRisRingExt R). apply Rmul_ext. apply CReq_refl. - apply CReq_sym, CRplus_0_r. - destruct (CRisRing R). apply CRmult_plus_distr_l. -Qed. - -Lemma CRopp_mult_distr_r : forall (R : ConstructiveReals) (r1 r2 : CRcarrier R), - orderEq _ (CRlt R) (CRopp R (CRmult R r1 r2)) - (CRmult R r1 (CRopp R r2)). -Proof. - intros. apply (CRplus_eq_reg_l R (CRmult R r1 r2)). - destruct (CRisRing R). - apply (CReq_trans R _ (CRzero R)). apply Ropp_def. - apply (CReq_trans R _ (CRmult R r1 (CRplus R r2 (CRopp R r2)))). - 2: apply CRmult_plus_distr_l. - apply (CReq_trans R _ (CRmult R r1 (CRzero R))). - apply CReq_sym, CRmult_0_r. - destruct (CRisRingExt R). apply Rmul_ext. apply CReq_refl. - apply CReq_sym, Ropp_def. -Qed. - -Lemma CRopp_mult_distr_l : forall (R : ConstructiveReals) (r1 r2 : CRcarrier R), - orderEq _ (CRlt R) (CRopp R (CRmult R r1 r2)) - (CRmult R (CRopp R r1) r2). -Proof. - intros. apply (CReq_trans R _ (CRmult R r2 (CRopp R r1))). - apply (CReq_trans R _ (CRopp R (CRmult R r2 r1))). - apply (Ropp_ext (CRisRingExt R)). - apply CReq_sym, (Rmul_comm (CRisRing R)). - apply CRopp_mult_distr_r. - apply CReq_sym, (Rmul_comm (CRisRing R)). -Qed. - -Lemma CRmult_lt_compat_r : forall (R : ConstructiveReals) (r r1 r2 : CRcarrier R), - CRlt R (CRzero R) r - -> CRlt R r1 r2 - -> CRlt R (CRmult R r1 r) (CRmult R r2 r). -Proof. - intros. apply (CRplus_lt_reg_r R (CRopp R (CRmult R r1 r))). - apply (CRle_lt_trans R _ (CRzero R)). - apply (Ropp_def (CRisRing R)). - apply (CRlt_le_trans R _ (CRplus R (CRmult R r2 r) (CRmult R (CRopp R r1) r))). - apply (CRlt_le_trans R _ (CRmult R (CRplus R r2 (CRopp R r1)) r)). - apply CRmult_lt_0_compat. 2: exact H. - apply (CRplus_lt_reg_r R r1). - apply (CRle_lt_trans R _ r1). apply (Radd_0_l (CRisRing R)). - apply (CRlt_le_trans R _ r2 _ H0). - apply (CRle_trans R _ (CRplus R r2 (CRplus R (CRopp R r1) r1))). - apply (CRle_trans R _ (CRplus R r2 (CRzero R))). - destruct (CRplus_0_r R r2). exact H1. - apply CRplus_le_compat_l. destruct (CRplus_opp_l R r1). exact H1. - destruct (Radd_assoc (CRisRing R) r2 (CRopp R r1) r1). exact H2. - destruct (CRisRing R). - destruct (Rdistr_l r2 (CRopp R r1) r). exact H2. - apply CRplus_le_compat_l. destruct (CRopp_mult_distr_l R r1 r). - exact H1. -Qed. - -Lemma CRinv_r : forall (R : ConstructiveReals) (r:CRcarrier R) - (rnz : orderAppart _ (CRlt R) r (CRzero R)), - orderEq _ (CRlt R) (CRmult R r (CRinv R r rnz)) (CRone R). -Proof. - intros. apply (CReq_trans R _ (CRmult R (CRinv R r rnz) r)). - apply (CRisRing R). apply CRinv_l. -Qed. - -Lemma CRmult_lt_reg_r : forall (R : ConstructiveReals) (r r1 r2 : CRcarrier R), - CRlt R (CRzero R) r - -> CRlt R (CRmult R r1 r) (CRmult R r2 r) - -> CRlt R r1 r2. -Proof. - intros. apply (CRmult_lt_compat_r R (CRinv R r (inr H))) in H0. - 2: apply CRinv_0_lt_compat, H. - apply (CRle_lt_trans R _ (CRmult R (CRmult R r1 r) (CRinv R r (inr H)))). - - clear H0. apply (CRle_trans R _ (CRmult R r1 (CRone R))). - destruct (CRmult_1_r R r1). exact H0. - apply (CRle_trans R _ (CRmult R r1 (CRmult R r (CRinv R r (inr H))))). - destruct (Rmul_ext (CRisRingExt R) r1 r1 (CReq_refl R r1) - (CRmult R r (CRinv R r (inr H))) (CRone R)). - apply CRinv_r. exact H0. - destruct (Rmul_assoc (CRisRing R) r1 r (CRinv R r (inr H))). exact H1. - - apply (CRlt_le_trans R _ (CRmult R (CRmult R r2 r) (CRinv R r (inr H)))). - exact H0. clear H0. - apply (CRle_trans R _ (CRmult R r2 (CRone R))). - 2: destruct (CRmult_1_r R r2); exact H1. - apply (CRle_trans R _ (CRmult R r2 (CRmult R r (CRinv R r (inr H))))). - destruct (Rmul_assoc (CRisRing R) r2 r (CRinv R r (inr H))). exact H0. - destruct (Rmul_ext (CRisRingExt R) r2 r2 (CReq_refl R r2) - (CRmult R r (CRinv R r (inr H))) (CRone R)). - apply CRinv_r. exact H1. -Qed. - -Lemma CRmult_lt_reg_l : forall (R : ConstructiveReals) (r r1 r2 : CRcarrier R), - CRlt R (CRzero R) r - -> CRlt R (CRmult R r r1) (CRmult R r r2) - -> CRlt R r1 r2. -Proof. - intros. - destruct (Rmul_comm (CRisRing R) r r1) as [H1 _]. - apply (CRle_lt_trans R _ _ _ H1) in H0. clear H1. - destruct (Rmul_comm (CRisRing R) r r2) as [_ H1]. - apply (CRlt_le_trans R _ _ _ H0) in H1. clear H0. - apply CRmult_lt_reg_r in H1. - exact H1. exact H. -Qed. - -Lemma CRmult_le_compat_l : forall (R : ConstructiveReals) (r r1 r2 : CRcarrier R), - CRlt R (CRzero R) r - -> orderLe _ (CRlt R) r1 r2 - -> orderLe _ (CRlt R) (CRmult R r r1) (CRmult R r r2). -Proof. - intros. intro abs. apply CRmult_lt_reg_l in abs. - contradiction. exact H. -Qed. - -Lemma CRmult_le_compat_r : forall (R : ConstructiveReals) (r r1 r2 : CRcarrier R), - CRlt R (CRzero R) r - -> orderLe _ (CRlt R) r1 r2 - -> orderLe _ (CRlt R) (CRmult R r1 r) (CRmult R r2 r). -Proof. - intros. intro abs. apply CRmult_lt_reg_r in abs. - contradiction. exact H. -Qed. - -Lemma CRmult_eq_reg_r : forall (R : ConstructiveReals) (r r1 r2 : CRcarrier R), - orderAppart _ (CRlt R) (CRzero R) r - -> orderEq _ (CRlt R) (CRmult R r1 r) (CRmult R r2 r) - -> orderEq _ (CRlt R) r1 r2. -Proof. - intros. destruct H0,H. - - split. - + intro abs. apply H0. apply CRmult_lt_compat_r. - exact c. exact abs. - + intro abs. apply H1. apply CRmult_lt_compat_r. - exact c. exact abs. - - split. - + intro abs. apply H1. apply CRopp_lt_cancel. - apply (CRle_lt_trans R _ (CRmult R r1 (CRopp R r))). - apply CRopp_mult_distr_r. - apply (CRlt_le_trans R _ (CRmult R r2 (CRopp R r))). - 2: apply CRopp_mult_distr_r. - apply CRmult_lt_compat_r. 2: exact abs. - apply (CRplus_lt_reg_r R r). apply (CRle_lt_trans R _ r). - apply (Radd_0_l (CRisRing R)). - apply (CRlt_le_trans R _ (CRzero R) _ c). - apply CRplus_opp_l. - + intro abs. apply H0. apply CRopp_lt_cancel. - apply (CRle_lt_trans R _ (CRmult R r2 (CRopp R r))). - apply CRopp_mult_distr_r. - apply (CRlt_le_trans R _ (CRmult R r1 (CRopp R r))). - 2: apply CRopp_mult_distr_r. - apply CRmult_lt_compat_r. 2: exact abs. - apply (CRplus_lt_reg_r R r). apply (CRle_lt_trans R _ r). - apply (Radd_0_l (CRisRing R)). - apply (CRlt_le_trans R _ (CRzero R) _ c). - apply CRplus_opp_l. -Qed. - -Lemma CR_of_Q_proper : forall (R : ConstructiveReals) (q r : Q), - q == r -> orderEq _ (CRlt R) (CR_of_Q R q) (CR_of_Q R r). -Proof. - split. - - intro abs. apply lt_CR_of_Q in abs. rewrite H in abs. - exact (Qlt_not_le r r abs (Qle_refl r)). - - intro abs. apply lt_CR_of_Q in abs. rewrite H in abs. - exact (Qlt_not_le r r abs (Qle_refl r)). -Qed. - -Lemma CR_of_Q_zero : forall (R : ConstructiveReals), - orderEq _ (CRlt R) (CR_of_Q R 0) (CRzero R). -Proof. - intros. apply CRzero_double. - apply (CReq_trans R _ (CR_of_Q R (0+0))). apply CR_of_Q_proper. - reflexivity. apply CR_of_Q_plus. -Qed. - -Lemma CR_of_Q_opp : forall (R : ConstructiveReals) (q : Q), - orderEq _ (CRlt R) (CR_of_Q R (-q)) (CRopp R (CR_of_Q R q)). -Proof. - intros. apply (CRplus_eq_reg_l R (CR_of_Q R q)). - apply (CReq_trans R _ (CRzero R)). - apply (CReq_trans R _ (CR_of_Q R (q-q))). - apply CReq_sym, CR_of_Q_plus. - apply (CReq_trans R _ (CR_of_Q R 0)). - apply CR_of_Q_proper. ring. apply CR_of_Q_zero. - apply CReq_sym. apply (CRisRing R). -Qed. - -Lemma CR_of_Q_le : forall (R : ConstructiveReals) (r q : Q), - Qle r q - -> orderLe _ (CRlt R) (CR_of_Q R r) (CR_of_Q R q). -Proof. - intros. intro abs. apply lt_CR_of_Q in abs. - exact (Qlt_not_le _ _ abs H). -Qed. - -Lemma CR_of_Q_pos : forall (R : ConstructiveReals) (q:Q), - Qlt 0 q -> CRlt R (CRzero R) (CR_of_Q R q). -Proof. - intros. apply (CRle_lt_trans R _ (CR_of_Q R 0)). - apply CR_of_Q_zero. apply CR_of_Q_lt. exact H. -Qed. - -Lemma CR_cv_above_rat - : forall (R : ConstructiveReals) (xn : nat -> Q) (x : CRcarrier R) (q : Q), - CR_cv R (fun n : nat => CR_of_Q R (xn n)) x - -> CRlt R (CR_of_Q R q) x - -> { n : nat | forall p:nat, le n p -> Qlt q (xn p) }. -Proof. - intros. - destruct (CR_Q_dense R _ _ H0) as [r [H1 H2]]. - apply lt_CR_of_Q in H1. clear H0. - destruct (Qarchimedean (/(r-q))) as [p pmaj]. - destruct (H p) as [n nmaj]. - exists n. intros k lenk. specialize (nmaj k lenk) as [H3 _]. - apply (lt_CR_of_Q R), (CRlt_le_trans R _ (CRplus R x (CR_of_Q R (-1#p)))). - apply (CRlt_trans R _ (CRplus R (CR_of_Q R r) (CR_of_Q R (-1#p)))). - 2: apply CRplus_lt_compat_r, H2. - apply (CRlt_le_trans R _ (CR_of_Q R (r+(-1#p)))). - - apply CR_of_Q_lt. - apply (Qplus_lt_l _ _ (-(-1#p)-q)). field_simplify. - setoid_replace (-1*(-1#p)) with (1#p). 2: reflexivity. - apply (Qmult_lt_l _ _ (r-q)) in pmaj. - rewrite Qmult_inv_r in pmaj. apply Qlt_shift_div_r in pmaj. - 2: reflexivity. setoid_replace (-1*q + r) with (r-q). exact pmaj. - ring. intro abs. apply Qlt_minus_iff in H1. - rewrite abs in H1. inversion H1. - apply Qlt_minus_iff in H1. exact H1. - - apply CR_of_Q_plus. - - apply (CRplus_le_reg_r R (CRopp R x)). - apply (CRle_trans R _ (CR_of_Q R (-1#p))). 2: exact H3. clear H3. - apply (CRle_trans R _ (CRplus R (CRopp R x) (CRplus R x (CR_of_Q R (-1 # p))))). - exact (proj1 (Radd_comm (CRisRing R) _ _)). - apply (CRle_trans R _ (CRplus R (CRplus R (CRopp R x) x) (CR_of_Q R (-1 # p)))). - exact (proj2 (Radd_assoc (CRisRing R) _ _ _)). - apply (CRle_trans R _ (CRplus R (CRzero R) (CR_of_Q R (-1 # p)))). - apply CRplus_le_compat_r. exact (proj2 (CRplus_opp_l R _)). - exact (proj2 (Radd_0_l (CRisRing R) _)). -Qed. - -Lemma CR_cv_below_rat - : forall (R : ConstructiveReals) (xn : nat -> Q) (x : CRcarrier R) (q : Q), - CR_cv R (fun n : nat => CR_of_Q R (xn n)) x - -> CRlt R x (CR_of_Q R q) - -> { n : nat | forall p:nat, le n p -> Qlt (xn p) q }. -Proof. - intros. - destruct (CR_Q_dense R _ _ H0) as [r [H1 H2]]. - apply lt_CR_of_Q in H2. clear H0. - destruct (Qarchimedean (/(q-r))) as [p pmaj]. - destruct (H p) as [n nmaj]. - exists n. intros k lenk. specialize (nmaj k lenk) as [_ H4]. - apply (lt_CR_of_Q R), (CRle_lt_trans R _ (CRplus R x (CR_of_Q R (1#p)))). - - apply (CRplus_le_reg_r R (CRopp R x)). - apply (CRle_trans R _ (CR_of_Q R (1#p))). exact H4. clear H4. - apply (CRle_trans R _ (CRplus R (CRopp R x) (CRplus R x (CR_of_Q R (1 # p))))). - 2: exact (proj1 (Radd_comm (CRisRing R) _ _)). - apply (CRle_trans R _ (CRplus R (CRplus R (CRopp R x) x) (CR_of_Q R (1 # p)))). - 2: exact (proj1 (Radd_assoc (CRisRing R) _ _ _)). - apply (CRle_trans R _ (CRplus R (CRzero R) (CR_of_Q R (1 # p)))). - exact (proj1 (Radd_0_l (CRisRing R) _)). - apply CRplus_le_compat_r. exact (proj1 (CRplus_opp_l R _)). - - apply (CRlt_trans R _ (CRplus R (CR_of_Q R r) (CR_of_Q R (1 # p)))). - apply CRplus_lt_compat_r. exact H1. - apply (CRle_lt_trans R _ (CR_of_Q R (r + (1#p)))). - apply CR_of_Q_plus. apply CR_of_Q_lt. - apply (Qmult_lt_l _ _ (q-r)) in pmaj. - rewrite Qmult_inv_r in pmaj. apply Qlt_shift_div_r in pmaj. - apply (Qplus_lt_l _ _ (-r)). field_simplify. - setoid_replace (-1*r + q) with (q-r). exact pmaj. - ring. reflexivity. intro abs. apply Qlt_minus_iff in H2. - rewrite abs in H2. inversion H2. - apply Qlt_minus_iff in H2. exact H2. -Qed. - -Lemma CR_cv_const : forall (R : ConstructiveReals) (x y : CRcarrier R), - CR_cv R (fun _ => x) y -> orderEq _ (CRlt R) x y. -Proof. - intros. destruct (CRisRing R). split. - - intro abs. - destruct (CR_Q_dense R x y abs) as [q [H0 H1]]. - destruct (CR_Q_dense R _ _ H1) as [r [H2 H3]]. - apply lt_CR_of_Q in H2. - destruct (Qarchimedean (/(r-q))) as [p pmaj]. - destruct (H p) as [n nmaj]. specialize (nmaj n (le_refl n)) as [nmaj _]. - apply nmaj. clear nmaj. - apply (CRlt_trans R _ (CR_of_Q R (q-r))). - apply (CRlt_le_trans R _ (CRplus R (CR_of_Q R q) (CRopp R (CR_of_Q R r)))). - + apply CRplus_lt_le_compat. exact H0. - intro H4. apply CRopp_lt_cancel in H4. exact (CRlt_asym R _ _ H4 H3). - + apply (CRle_trans R _ (CRplus R (CR_of_Q R q) (CR_of_Q R (-r)))). - apply CRplus_le_compat_l. exact (proj1 (CR_of_Q_opp R r)). - exact (proj1 (CR_of_Q_plus R _ _)). - + apply CR_of_Q_lt. - apply (Qplus_lt_l _ _ (-(-1#p)+r-q)). field_simplify. - setoid_replace (-1*(-1#p)) with (1#p). 2: reflexivity. - apply (Qmult_lt_l _ _ (r-q)) in pmaj. - rewrite Qmult_inv_r in pmaj. apply Qlt_shift_div_r in pmaj. - 2: reflexivity. setoid_replace (-1*q + r) with (r-q). exact pmaj. - ring. intro H4. apply Qlt_minus_iff in H2. - rewrite H4 in H2. inversion H2. - apply Qlt_minus_iff in H2. exact H2. - - intro abs. - destruct (CR_Q_dense R _ _ abs) as [q [H0 H1]]. - destruct (CR_Q_dense R _ _ H0) as [r [H2 H3]]. - apply lt_CR_of_Q in H3. - destruct (Qarchimedean (/(q-r))) as [p pmaj]. - destruct (H p) as [n nmaj]. specialize (nmaj n (le_refl n)) as [_ nmaj]. - apply nmaj. clear nmaj. - apply (CRlt_trans R _ (CR_of_Q R (q-r))). - + apply CR_of_Q_lt. - apply (Qmult_lt_l _ _ (q-r)) in pmaj. - rewrite Qmult_inv_r in pmaj. apply Qlt_shift_div_r in pmaj. - exact pmaj. reflexivity. - intro H4. apply Qlt_minus_iff in H3. - rewrite H4 in H3. inversion H3. - apply Qlt_minus_iff in H3. exact H3. - + apply (CRle_lt_trans R _ (CRplus R (CR_of_Q R q) (CR_of_Q R (-r)))). - apply CR_of_Q_plus. - apply (CRle_lt_trans R _ (CRplus R (CR_of_Q R q) (CRopp R (CR_of_Q R r)))). - apply CRplus_le_compat_l. exact (proj2 (CR_of_Q_opp R r)). - apply CRplus_lt_le_compat. exact H1. - intro H4. apply CRopp_lt_cancel in H4. - exact (CRlt_asym R _ _ H4 H2). -Qed. diff --git a/theories/Reals/ConstructiveRealsLUB.v b/theories/Reals/ConstructiveRealsLUB.v deleted file mode 100644 index cc18bd910d..0000000000 --- a/theories/Reals/ConstructiveRealsLUB.v +++ /dev/null @@ -1,318 +0,0 @@ -(************************************************************************) -(* * The Coq Proof Assistant / The Coq Development Team *) -(* v * Copyright INRIA, CNRS and contributors *) -(* <O___,, * (see version control and CREDITS file for authors & dates) *) -(* \VV/ **************************************************************) -(* // * This file is distributed under the terms of the *) -(* * GNU Lesser General Public License Version 2.1 *) -(* * (see LICENSE file for the text of the license) *) -(************************************************************************) -(************************************************************************) - -(* Proof that LPO and the excluded middle for negations imply - the existence of least upper bounds for all non-empty and bounded - subsets of the real numbers. *) - -Require Import QArith_base. -Require Import Qabs. -Require Import ConstructiveReals. -Require Import ConstructiveCauchyRealsMult. -Require Import ConstructiveRealsMorphisms. -Require Import ConstructiveRcomplete. -Require Import Logic.ConstructiveEpsilon. - -Local Open Scope CReal_scope. - -Definition sig_forall_dec_T : Type - := forall (P : nat -> Prop), (forall n, {P n} + {~P n}) - -> {n | ~P n} + {forall n, P n}. - -Definition sig_not_dec_T : Type := forall P : Prop, { ~~P } + { ~P }. - -Definition is_upper_bound (E:CReal -> Prop) (m:CReal) - := forall x:CReal, E x -> x <= m. - -Definition is_lub (E:CReal -> Prop) (m:CReal) := - is_upper_bound E m /\ (forall b:CReal, is_upper_bound E b -> m <= b). - -Lemma is_upper_bound_dec : - forall (E:CReal -> Prop) (x:CReal), - sig_forall_dec_T - -> sig_not_dec_T - -> { is_upper_bound E x } + { ~is_upper_bound E x }. -Proof. - intros E x lpo sig_not_dec. - destruct (sig_not_dec (~exists y:CReal, E y /\ CRealLtProp x y)). - - left. intros y H. - destruct (CRealLt_lpo_dec x y lpo). 2: exact f. - exfalso. apply n. intro abs. apply abs. - exists y. split. exact H. destruct c. exists x0. exact q. - - right. intro abs. apply n. intros [y [H H0]]. - specialize (abs y H). apply CRealLtEpsilon in H0. contradiction. -Qed. - -Lemma is_upper_bound_epsilon : - forall (E:CReal -> Prop), - sig_forall_dec_T - -> sig_not_dec_T - -> (exists x:CReal, is_upper_bound E x) - -> { n:nat | is_upper_bound E (inject_Q (Z.of_nat n # 1)) }. -Proof. - intros E lpo sig_not_dec Ebound. - apply constructive_indefinite_ground_description_nat. - - intro n. apply is_upper_bound_dec. exact lpo. exact sig_not_dec. - - destruct Ebound as [x H]. destruct (Rup_pos x). exists (Pos.to_nat x0). - intros y ey. specialize (H y ey). - apply CRealLt_asym. apply (CReal_le_lt_trans _ x). - exact H. rewrite positive_nat_Z. exact c. -Qed. - -Lemma is_upper_bound_not_epsilon : - forall E:CReal -> Prop, - sig_forall_dec_T - -> sig_not_dec_T - -> (exists x : CReal, E x) - -> { m:nat | ~is_upper_bound E (-inject_Q (Z.of_nat m # 1)) }. -Proof. - intros E lpo sig_not_dec H. - apply constructive_indefinite_ground_description_nat. - - intro n. destruct (is_upper_bound_dec E (-inject_Q (Z.of_nat n # 1)) lpo sig_not_dec). - right. intro abs. contradiction. left. exact n0. - - destruct H as [x H]. destruct (Rup_pos (-x)) as [n H0]. - exists (Pos.to_nat n). intro abs. specialize (abs x H). - apply abs. rewrite positive_nat_Z. - apply (CReal_plus_lt_reg_l (inject_Q (Z.pos n # 1)-x)). - ring_simplify. exact H0. -Qed. - -(* Decidable Dedekind cuts are Cauchy reals. *) -Record DedekindDecCut : Type := - { - DDupcut : Q -> Prop; - DDproper : forall q r : Q, (q == r -> DDupcut q -> DDupcut r)%Q; - DDlow : Q; - DDhigh : Q; - DDdec : forall q:Q, { DDupcut q } + { ~DDupcut q }; - DDinterval : forall q r : Q, Qle q r -> DDupcut q -> DDupcut r; - DDhighProp : DDupcut DDhigh; - DDlowProp : ~DDupcut DDlow; - }. - -Lemma DDlow_below_up : forall (upcut : DedekindDecCut) (a b : Q), - DDupcut upcut a -> ~DDupcut upcut b -> Qlt b a. -Proof. - intros. destruct (Qlt_le_dec b a). exact q. - exfalso. apply H0. apply (DDinterval upcut a). - exact q. exact H. -Qed. - -Fixpoint DDcut_limit_fix (upcut : DedekindDecCut) (r : Q) (n : nat) : - Qlt 0 r - -> (DDupcut upcut (DDlow upcut + (Z.of_nat n#1) * r)) - -> { q : Q | DDupcut upcut q /\ ~DDupcut upcut (q - r) }. -Proof. - destruct n. - - intros. exfalso. simpl in H0. - apply (DDproper upcut _ (DDlow upcut)) in H0. 2: ring. - exact (DDlowProp upcut H0). - - intros. destruct (DDdec upcut (DDlow upcut + (Z.of_nat n # 1) * r)). - + exact (DDcut_limit_fix upcut r n H d). - + exists (DDlow upcut + (Z.of_nat (S n) # 1) * r)%Q. split. - exact H0. intro abs. - apply (DDproper upcut _ (DDlow upcut + (Z.of_nat n # 1) * r)) in abs. - contradiction. - rewrite Nat2Z.inj_succ. unfold Z.succ. rewrite <- Qinv_plus_distr. - ring. -Qed. - -Lemma DDcut_limit : forall (upcut : DedekindDecCut) (r : Q), - Qlt 0 r - -> { q : Q | DDupcut upcut q /\ ~DDupcut upcut (q - r) }. -Proof. - intros. - destruct (Qarchimedean ((DDhigh upcut - DDlow upcut)/r)) as [n nmaj]. - apply (DDcut_limit_fix upcut r (Pos.to_nat n) H). - apply (Qmult_lt_r _ _ r) in nmaj. 2: exact H. - unfold Qdiv in nmaj. - rewrite <- Qmult_assoc, (Qmult_comm (/r)), Qmult_inv_r, Qmult_1_r in nmaj. - apply (DDinterval upcut (DDhigh upcut)). 2: exact (DDhighProp upcut). - apply Qlt_le_weak. apply (Qplus_lt_r _ _ (-DDlow upcut)). - rewrite Qplus_assoc, <- (Qplus_comm (DDlow upcut)), Qplus_opp_r, - Qplus_0_l, Qplus_comm. - rewrite positive_nat_Z. exact nmaj. - intros abs. rewrite abs in H. exact (Qlt_irrefl 0 H). -Qed. - -Lemma glb_dec_Q : forall upcut : DedekindDecCut, - { x : CReal | forall r:Q, (x < inject_Q r -> DDupcut upcut r) - /\ (inject_Q r < x -> ~DDupcut upcut r) }. -Proof. - intros. - assert (forall a b : Q, Qle a b -> Qle (-b) (-a)). - { intros. apply (Qplus_le_l _ _ (a+b)). ring_simplify. exact H. } - assert (QCauchySeq (fun n:nat => proj1_sig (DDcut_limit - upcut (1#Pos.of_nat n) (eq_refl _))) - Pos.to_nat). - { intros p i j pi pj. - destruct (DDcut_limit upcut (1 # Pos.of_nat i) eq_refl), - (DDcut_limit upcut (1 # Pos.of_nat j) eq_refl); unfold proj1_sig. - apply Qabs_case. intros. - apply (Qplus_lt_l _ _ (x0- (1#p))). ring_simplify. - setoid_replace (x + -1 * (1 # p))%Q with (x - (1 # p))%Q. - 2: ring. apply (Qle_lt_trans _ (x- (1#Pos.of_nat i))). - apply Qplus_le_r. apply H. - apply Z2Nat.inj_le. discriminate. discriminate. simpl. - rewrite Nat2Pos.id. exact pi. intro abs. - subst i. inversion pi. pose proof (Pos2Nat.is_pos p). - rewrite H2 in H1. inversion H1. - apply (DDlow_below_up upcut). apply a0. apply a. - intros. - apply (Qplus_lt_l _ _ (x- (1#p))). ring_simplify. - setoid_replace (x0 + -1 * (1 # p))%Q with (x0 - (1 # p))%Q. - 2: ring. apply (Qle_lt_trans _ (x0- (1#Pos.of_nat j))). - apply Qplus_le_r. apply H. - apply Z2Nat.inj_le. discriminate. discriminate. simpl. - rewrite Nat2Pos.id. exact pj. intro abs. - subst j. inversion pj. pose proof (Pos2Nat.is_pos p). - rewrite H2 in H1. inversion H1. - apply (DDlow_below_up upcut). apply a. apply a0. } - pose (exist (fun qn => QSeqEquiv qn qn Pos.to_nat) _ H0) as l. - exists l. split. - - intros. (* find an upper point between the limit and r *) - destruct H1 as [p pmaj]. - unfold l,proj1_sig in pmaj. - destruct (DDcut_limit upcut (1 # Pos.of_nat (Pos.to_nat p)) eq_refl) as [q qmaj] - ; simpl in pmaj. - apply (DDinterval upcut q). 2: apply qmaj. - apply (Qplus_lt_l _ _ q) in pmaj. ring_simplify in pmaj. - apply (Qle_trans _ ((2#p) + q)). - apply (Qplus_le_l _ _ (-q)). ring_simplify. discriminate. - apply Qlt_le_weak. exact pmaj. - - intros [p pmaj] abs. - unfold l,proj1_sig in pmaj. - destruct (DDcut_limit upcut (1 # Pos.of_nat (Pos.to_nat p)) eq_refl) as [q qmaj] - ; simpl in pmaj. - rewrite Pos2Nat.id in qmaj. - apply (Qplus_lt_r _ _ (r - (2#p))) in pmaj. ring_simplify in pmaj. - destruct qmaj. apply H2. - apply (DDinterval upcut r). 2: exact abs. - apply Qlt_le_weak, (Qlt_trans _ (-1*(2#p) + q) _ pmaj). - apply (Qplus_lt_l _ _ ((2#p) -q)). ring_simplify. - setoid_replace (-1 * (1 # p))%Q with (-(1#p))%Q. - 2: ring. rewrite Qinv_minus_distr. reflexivity. -Qed. - -Lemma is_upper_bound_glb : - forall (E:CReal -> Prop), - sig_not_dec_T - -> sig_forall_dec_T - -> (exists x : CReal, E x) - -> (exists x : CReal, is_upper_bound E x) - -> { x : CReal | forall r:Q, (x < inject_Q r -> is_upper_bound E (inject_Q r)) - /\ (inject_Q r < x -> ~is_upper_bound E (inject_Q r)) }. -Proof. - intros E sig_not_dec lpo Einhab Ebound. - destruct (is_upper_bound_epsilon E lpo sig_not_dec Ebound) as [a luba]. - destruct (is_upper_bound_not_epsilon E lpo sig_not_dec Einhab) as [b glbb]. - pose (fun q => is_upper_bound E (inject_Q q)) as upcut. - assert (forall q:Q, { upcut q } + { ~upcut q } ). - { intro q. apply is_upper_bound_dec. exact lpo. exact sig_not_dec. } - assert (forall q r : Q, (q <= r)%Q -> upcut q -> upcut r). - { intros. intros x Ex. specialize (H1 x Ex). intro abs. - apply H1. apply (CReal_le_lt_trans _ (inject_Q r)). 2: exact abs. - apply inject_Q_le. exact H0. } - assert (upcut (Z.of_nat a # 1)%Q). - { intros x Ex. exact (luba x Ex). } - assert (~upcut (- Z.of_nat b # 1)%Q). - { intros abs. apply glbb. intros x Ex. - specialize (abs x Ex). rewrite <- opp_inject_Q. - exact abs. } - assert (forall q r : Q, (q == r)%Q -> upcut q -> upcut r). - { intros. intros x Ex. specialize (H4 x Ex). rewrite <- H3. exact H4. } - destruct (glb_dec_Q (Build_DedekindDecCut - upcut H3 (-Z.of_nat b # 1)%Q (Z.of_nat a # 1) - H H0 H1 H2)). - simpl in a0. exists x. intro r. split. - - intros. apply a0. exact H4. - - intros H6 abs. specialize (a0 r) as [_ a0]. apply a0. - exact H6. exact abs. -Qed. - -Lemma is_upper_bound_closed : - forall (E:CReal -> Prop) (sig_forall_dec : sig_forall_dec_T) - (sig_not_dec : sig_not_dec_T) - (Einhab : exists x : CReal, E x) - (Ebound : exists x : CReal, is_upper_bound E x), - is_lub - E (proj1_sig (is_upper_bound_glb - E sig_not_dec sig_forall_dec Einhab Ebound)). -Proof. - intros. split. - - intros x Ex. - destruct (is_upper_bound_glb E sig_not_dec sig_forall_dec Einhab Ebound); simpl. - intro abs. destruct (FQ_dense x0 x abs) as [q [qmaj H]]. - specialize (a q) as [a _]. specialize (a qmaj x Ex). - contradiction. - - intros. - destruct (is_upper_bound_glb E sig_not_dec sig_forall_dec Einhab Ebound); simpl. - intro abs. destruct (FQ_dense b x abs) as [q [qmaj H0]]. - specialize (a q) as [_ a]. apply a. exact H0. - intros y Ey. specialize (H y Ey). intro abs2. - apply H. exact (CReal_lt_trans _ (inject_Q q) _ qmaj abs2). -Qed. - -Lemma sig_lub : - forall (E:CReal -> Prop), - sig_forall_dec_T - -> sig_not_dec_T - -> (exists x : CReal, E x) - -> (exists x : CReal, is_upper_bound E x) - -> { u : CReal | is_lub E u }. -Proof. - intros E sig_forall_dec sig_not_dec Einhab Ebound. - pose proof (is_upper_bound_closed E sig_forall_dec sig_not_dec Einhab Ebound). - destruct (is_upper_bound_glb - E sig_not_dec sig_forall_dec Einhab Ebound); simpl in H. - exists x. exact H. -Qed. - -Definition CRis_upper_bound (R : ConstructiveReals) (E:CRcarrier R -> Prop) (m:CRcarrier R) - := forall x:CRcarrier R, E x -> CRlt R m x -> False. - -Lemma CR_sig_lub : - forall (R : ConstructiveReals) (E:CRcarrier R -> Prop), - (forall x y : CRcarrier R, orderEq _ (CRlt R) x y -> (E x <-> E y)) - -> sig_forall_dec_T - -> sig_not_dec_T - -> (exists x : CRcarrier R, E x) - -> (exists x : CRcarrier R, CRis_upper_bound R E x) - -> { u : CRcarrier R | CRis_upper_bound R E u /\ - forall y:CRcarrier R, CRis_upper_bound R E y -> CRlt R y u -> False }. -Proof. - intros. destruct (sig_lub (fun x:CReal => E (CauchyMorph R x)) X X0) as [u ulub]. - - destruct H0. exists (CauchyMorph_inv R x). - specialize (H (CauchyMorph R (CauchyMorph_inv R x)) x - (CauchyMorph_surject R x)) as [_ H]. - exact (H H0). - - destruct H1. exists (CauchyMorph_inv R x). - intros y Ey. specialize (H1 (CauchyMorph R y) Ey). - intros abs. apply H1. - apply (CauchyMorph_increasing R) in abs. - apply (CRle_lt_trans R _ (CauchyMorph R (CauchyMorph_inv R x))). - 2: exact abs. apply (CauchyMorph_surject R x). - - exists (CauchyMorph R u). destruct ulub. split. - + intros y Ey abs. specialize (H2 (CauchyMorph_inv R y)). - simpl in H2. - specialize (H (CauchyMorph R (CauchyMorph_inv R y)) y - (CauchyMorph_surject R y)) as [_ H]. - specialize (H2 (H Ey)). apply H2. - apply CauchyMorph_inv_increasing in abs. - rewrite CauchyMorph_inject in abs. exact abs. - + intros. apply (H3 (CauchyMorph_inv R y)). - intros z Ez abs. specialize (H4 (CauchyMorph R z)). - apply (H4 Ez). apply (CauchyMorph_increasing R) in abs. - apply (CRle_lt_trans R _ (CauchyMorph R (CauchyMorph_inv R y))). - 2: exact abs. apply (CauchyMorph_surject R y). - apply CauchyMorph_inv_increasing in H5. - rewrite CauchyMorph_inject in H5. exact H5. -Qed. diff --git a/theories/Reals/ConstructiveRealsMorphisms.v b/theories/Reals/ConstructiveRealsMorphisms.v deleted file mode 100644 index 4af95e2980..0000000000 --- a/theories/Reals/ConstructiveRealsMorphisms.v +++ /dev/null @@ -1,1158 +0,0 @@ -(************************************************************************) -(* * The Coq Proof Assistant / The Coq Development Team *) -(* v * Copyright INRIA, CNRS and contributors *) -(* <O___,, * (see version control and CREDITS file for authors & dates) *) -(* \VV/ **************************************************************) -(* // * This file is distributed under the terms of the *) -(* * GNU Lesser General Public License Version 2.1 *) -(* * (see LICENSE file for the text of the license) *) -(************************************************************************) -(************************************************************************) - -(** Morphisms used to transport results from any instance of - ConstructiveReals to any other. - Between any two constructive reals structures R1 and R2, - all morphisms R1 -> R2 are extensionally equal. We will - further show that they exist, and so are isomorphisms. - The difference between two morphisms R1 -> R2 is therefore - the speed of computation. - - The canonical isomorphisms we provide here are often very slow, - when a new implementation of constructive reals is added, - it should define its own ad hoc isomorphisms for better speed. - - Apart from the speed, those unique isomorphisms also serve as - sanity checks of the interface ConstructiveReals : - it captures a concept with a strong notion of uniqueness. *) - -Require Import QArith. -Require Import Qabs. -Require Import ConstructiveReals. -Require Import ConstructiveCauchyRealsMult. -Require Import ConstructiveRcomplete. - - -Record ConstructiveRealsMorphism (R1 R2 : ConstructiveReals) : Set := - { - CRmorph : CRcarrier R1 -> CRcarrier R2; - CRmorph_rat : forall q : Q, - orderEq _ (CRlt R2) (CRmorph (CR_of_Q R1 q)) (CR_of_Q R2 q); - CRmorph_increasing : forall x y : CRcarrier R1, - CRlt R1 x y -> CRlt R2 (CRmorph x) (CRmorph y); - }. - - -Lemma CRmorph_increasing_inv - : forall (R1 R2 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2) - (x y : CRcarrier R1), - CRlt R2 (CRmorph _ _ f x) (CRmorph _ _ f y) - -> CRlt R1 x y. -Proof. - intros. destruct (CR_Q_dense R2 _ _ H) as [q [H0 H1]]. - destruct (CR_Q_dense R2 _ _ H0) as [r [H2 H3]]. - apply lt_CR_of_Q, (CR_of_Q_lt R1) in H3. - destruct (CRltLinear R1). - destruct (s _ x _ H3). - - exfalso. apply (CRmorph_increasing _ _ f) in c. - destruct (CRmorph_rat _ _ f r) as [H4 _]. - apply (CRle_lt_trans R2 _ _ _ H4) in c. clear H4. - exact (CRlt_asym R2 _ _ c H2). - - clear H2 H3 r. apply (CRlt_trans R1 _ _ _ c). clear c. - destruct (CR_Q_dense R2 _ _ H1) as [t [H2 H3]]. - apply lt_CR_of_Q, (CR_of_Q_lt R1) in H2. - destruct (s _ y _ H2). exact c. - exfalso. apply (CRmorph_increasing _ _ f) in c. - destruct (CRmorph_rat _ _ f t) as [_ H4]. - apply (CRlt_le_trans R2 _ _ _ c) in H4. clear c. - exact (CRlt_asym R2 _ _ H4 H3). -Qed. - -Lemma CRmorph_unique : forall (R1 R2 : ConstructiveReals) - (f g : ConstructiveRealsMorphism R1 R2) - (x : CRcarrier R1), - orderEq _ (CRlt R2) (CRmorph _ _ f x) (CRmorph _ _ g x). -Proof. - split. - - intro abs. destruct (CR_Q_dense R2 _ _ abs) as [q [H H0]]. - destruct (CRmorph_rat _ _ f q) as [H1 _]. - apply (CRlt_le_trans R2 _ _ _ H) in H1. clear H. - apply CRmorph_increasing_inv in H1. - destruct (CRmorph_rat _ _ g q) as [_ H2]. - apply (CRle_lt_trans R2 _ _ _ H2) in H0. clear H2. - apply CRmorph_increasing_inv in H0. - exact (CRlt_asym R1 _ _ H0 H1). - - intro abs. destruct (CR_Q_dense R2 _ _ abs) as [q [H H0]]. - destruct (CRmorph_rat _ _ f q) as [_ H1]. - apply (CRle_lt_trans R2 _ _ _ H1) in H0. clear H1. - apply CRmorph_increasing_inv in H0. - destruct (CRmorph_rat _ _ g q) as [H2 _]. - apply (CRlt_le_trans R2 _ _ _ H) in H2. clear H. - apply CRmorph_increasing_inv in H2. - exact (CRlt_asym R1 _ _ H0 H2). -Qed. - - -(* The identity is the only endomorphism of constructive reals. - For any ConstructiveReals R1, R2 and any morphisms - f : R1 -> R2 and g : R2 -> R1, - f and g are isomorphisms and are inverses of each other. *) -Lemma Endomorph_id : forall (R : ConstructiveReals) (f : ConstructiveRealsMorphism R R) - (x : CRcarrier R), - orderEq _ (CRlt R) (CRmorph _ _ f x) x. -Proof. - split. - - intro abs. destruct (CR_Q_dense R _ _ abs) as [q [H0 H1]]. - destruct (CRmorph_rat _ _ f q) as [H _]. - apply (CRlt_le_trans R _ _ _ H0) in H. clear H0. - apply CRmorph_increasing_inv in H. - exact (CRlt_asym R _ _ H1 H). - - intro abs. destruct (CR_Q_dense R _ _ abs) as [q [H0 H1]]. - destruct (CRmorph_rat _ _ f q) as [_ H]. - apply (CRle_lt_trans R _ _ _ H) in H1. clear H. - apply CRmorph_increasing_inv in H1. - exact (CRlt_asym R _ _ H1 H0). -Qed. - -Lemma CRmorph_proper : forall (R1 R2 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2) - (x y : CRcarrier R1), - orderEq _ (CRlt R1) x y - -> orderEq _ (CRlt R2) (CRmorph _ _ f x) (CRmorph _ _ f y). -Proof. - split. - - intro abs. apply CRmorph_increasing_inv in abs. - destruct H. contradiction. - - intro abs. apply CRmorph_increasing_inv in abs. - destruct H. contradiction. -Qed. - -Definition CRmorph_compose (R1 R2 R3 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2) - (g : ConstructiveRealsMorphism R2 R3) - : ConstructiveRealsMorphism R1 R3. -Proof. - apply (Build_ConstructiveRealsMorphism - R1 R3 (fun x:CRcarrier R1 => CRmorph _ _ g (CRmorph _ _ f x))). - - intro q. apply (CReq_trans R3 _ (CRmorph R2 R3 g (CR_of_Q R2 q))). - apply CRmorph_proper. apply CRmorph_rat. apply CRmorph_rat. - - intros. apply CRmorph_increasing. apply CRmorph_increasing. exact H. -Defined. - -Lemma CRmorph_le : forall (R1 R2 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2) - (x y : CRcarrier R1), - orderLe _ (CRlt R1) x y - -> orderLe _ (CRlt R2) (CRmorph _ _ f x) (CRmorph _ _ f y). -Proof. - intros. intro abs. apply CRmorph_increasing_inv in abs. contradiction. -Qed. - -Lemma CRmorph_le_inv : forall (R1 R2 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2) - (x y : CRcarrier R1), - orderLe _ (CRlt R2) (CRmorph _ _ f x) (CRmorph _ _ f y) - -> orderLe _ (CRlt R1) x y. -Proof. - intros. intro abs. apply (CRmorph_increasing _ _ f) in abs. contradiction. -Qed. - -Lemma CRmorph_zero : forall (R1 R2 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2), - orderEq _ (CRlt R2) (CRmorph _ _ f (CRzero R1)) (CRzero R2). -Proof. - intros. apply (CReq_trans R2 _ (CRmorph _ _ f (CR_of_Q R1 0))). - apply CRmorph_proper. apply CReq_sym, CR_of_Q_zero. - apply (CReq_trans R2 _ (CR_of_Q R2 0)). - apply CRmorph_rat. apply CR_of_Q_zero. -Qed. - -Lemma CRmorph_one : forall (R1 R2 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2), - orderEq _ (CRlt R2) (CRmorph _ _ f (CRone R1)) (CRone R2). -Proof. - intros. apply (CReq_trans R2 _ (CRmorph _ _ f (CR_of_Q R1 1))). - apply CRmorph_proper. apply CReq_sym, CR_of_Q_one. - apply (CReq_trans R2 _ (CR_of_Q R2 1)). - apply CRmorph_rat. apply CR_of_Q_one. -Qed. - -Lemma CRmorph_opp : forall (R1 R2 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2) - (x : CRcarrier R1), - orderEq _ (CRlt R2) (CRmorph _ _ f (CRopp R1 x)) - (CRopp R2 (CRmorph _ _ f x)). -Proof. - split. - - intro abs. - destruct (CR_Q_dense R2 _ _ abs) as [q [H H0]]. clear abs. - destruct (CRmorph_rat R1 R2 f q) as [H1 _]. - apply (CRlt_le_trans R2 _ _ _ H) in H1. clear H. - apply CRmorph_increasing_inv in H1. - apply CRopp_gt_lt_contravar in H0. - destruct (CR_of_Q_opp R2 q) as [H2 _]. - apply (CRlt_le_trans R2 _ _ _ H0) in H2. clear H0. - pose proof (CRopp_involutive R2 (CRmorph R1 R2 f x)) as [H _]. - apply (CRle_lt_trans R2 _ _ _ H) in H2. clear H. - destruct (CRmorph_rat R1 R2 f (-q)) as [H _]. - apply (CRlt_le_trans R2 _ _ _ H2) in H. clear H2. - apply CRmorph_increasing_inv in H. - destruct (CR_of_Q_opp R1 q) as [_ H2]. - apply (CRlt_le_trans R1 _ _ _ H) in H2. clear H. - apply CRopp_gt_lt_contravar in H2. - pose proof (CRopp_involutive R1 (CR_of_Q R1 q)) as [H _]. - apply (CRle_lt_trans R1 _ _ _ H) in H2. clear H. - exact (CRlt_asym R1 _ _ H1 H2). - - intro abs. - destruct (CR_Q_dense R2 _ _ abs) as [q [H H0]]. clear abs. - destruct (CRmorph_rat R1 R2 f q) as [_ H1]. - apply (CRle_lt_trans R2 _ _ _ H1) in H0. clear H1. - apply CRmorph_increasing_inv in H0. - apply CRopp_gt_lt_contravar in H. - pose proof (CRopp_involutive R2 (CRmorph R1 R2 f x)) as [_ H1]. - apply (CRlt_le_trans R2 _ _ _ H) in H1. clear H. - destruct (CR_of_Q_opp R2 q) as [_ H2]. - apply (CRle_lt_trans R2 _ _ _ H2) in H1. clear H2. - destruct (CRmorph_rat R1 R2 f (-q)) as [_ H]. - apply (CRle_lt_trans R2 _ _ _ H) in H1. clear H. - apply CRmorph_increasing_inv in H1. - destruct (CR_of_Q_opp R1 q) as [H2 _]. - apply (CRle_lt_trans R1 _ _ _ H2) in H1. clear H2. - apply CRopp_gt_lt_contravar in H1. - pose proof (CRopp_involutive R1 (CR_of_Q R1 q)) as [_ H]. - apply (CRlt_le_trans R1 _ _ _ H1) in H. clear H1. - exact (CRlt_asym R1 _ _ H0 H). -Qed. - -Lemma CRplus_pos_rat_lt : forall (R : ConstructiveReals) (x : CRcarrier R) (q : Q), - Qlt 0 q -> CRlt R x (CRplus R x (CR_of_Q R q)). -Proof. - intros. - apply (CRle_lt_trans R _ (CRplus R x (CRzero R))). apply CRplus_0_r. - apply CRplus_lt_compat_l. - apply (CRle_lt_trans R _ (CR_of_Q R 0)). apply CR_of_Q_zero. - apply CR_of_Q_lt. exact H. -Defined. - -Lemma CRplus_neg_rat_lt : forall (R : ConstructiveReals) (x : CRcarrier R) (q : Q), - Qlt q 0 -> CRlt R (CRplus R x (CR_of_Q R q)) x. -Proof. - intros. - apply (CRlt_le_trans R _ (CRplus R x (CRzero R))). 2: apply CRplus_0_r. - apply CRplus_lt_compat_l. - apply (CRlt_le_trans R _ (CR_of_Q R 0)). - apply CR_of_Q_lt. exact H. apply CR_of_Q_zero. -Qed. - -Lemma CRmorph_plus_rat : forall (R1 R2 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2) - (x : CRcarrier R1) (q : Q), - orderEq _ (CRlt R2) (CRmorph _ _ f (CRplus R1 x (CR_of_Q R1 q))) - (CRplus R2 (CRmorph _ _ f x) (CR_of_Q R2 q)). -Proof. - split. - - intro abs. - destruct (CR_Q_dense R2 _ _ abs) as [r [H H0]]. clear abs. - destruct (CRmorph_rat _ _ f r) as [H1 _]. - apply (CRlt_le_trans R2 _ _ _ H) in H1. clear H. - apply CRmorph_increasing_inv in H1. - apply (CRlt_asym R1 _ _ H1). clear H1. - apply (CRplus_lt_reg_r R1 (CRopp R1 (CR_of_Q R1 q))). - apply (CRlt_le_trans R1 _ x). - apply (CRle_lt_trans R1 _ (CR_of_Q R1 (r-q))). - apply (CRle_trans R1 _ (CRplus R1 (CR_of_Q R1 r) (CR_of_Q R1 (-q)))). - apply CRplus_le_compat_l. destruct (CR_of_Q_opp R1 q). exact H. - destruct (CR_of_Q_plus R1 r (-q)). exact H. - apply (CRmorph_increasing_inv _ _ f). - apply (CRle_lt_trans R2 _ (CR_of_Q R2 (r - q))). - apply CRmorph_rat. - apply (CRplus_lt_reg_r R2 (CR_of_Q R2 q)). - apply (CRle_lt_trans R2 _ (CR_of_Q R2 r)). 2: exact H0. - intro H. - destruct (CR_of_Q_plus R2 (r-q) q) as [H1 _]. - apply (CRlt_le_trans R2 _ _ _ H) in H1. clear H. - apply lt_CR_of_Q in H1. ring_simplify in H1. - exact (Qlt_not_le _ _ H1 (Qle_refl _)). - destruct (CRisRing R1). - apply (CRle_trans R1 _ (CRplus R1 x (CRplus R1 (CR_of_Q R1 q) (CRopp R1 (CR_of_Q R1 q))))). - apply (CRle_trans R1 _ (CRplus R1 x (CRzero R1))). - destruct (CRplus_0_r R1 x). exact H. - apply CRplus_le_compat_l. destruct (Ropp_def (CR_of_Q R1 q)). exact H. - destruct (Radd_assoc x (CR_of_Q R1 q) (CRopp R1 (CR_of_Q R1 q))). - exact H1. - - intro abs. - destruct (CR_Q_dense R2 _ _ abs) as [r [H H0]]. clear abs. - destruct (CRmorph_rat _ _ f r) as [_ H1]. - apply (CRle_lt_trans R2 _ _ _ H1) in H0. clear H1. - apply CRmorph_increasing_inv in H0. - apply (CRlt_asym R1 _ _ H0). clear H0. - apply (CRplus_lt_reg_r R1 (CRopp R1 (CR_of_Q R1 q))). - apply (CRle_lt_trans R1 _ x). - destruct (CRisRing R1). - apply (CRle_trans R1 _ (CRplus R1 x (CRplus R1 (CR_of_Q R1 q) (CRopp R1 (CR_of_Q R1 q))))). - destruct (Radd_assoc x (CR_of_Q R1 q) (CRopp R1 (CR_of_Q R1 q))). - exact H0. - apply (CRle_trans R1 _ (CRplus R1 x (CRzero R1))). - apply CRplus_le_compat_l. destruct (Ropp_def (CR_of_Q R1 q)). exact H1. - destruct (CRplus_0_r R1 x). exact H1. - apply (CRlt_le_trans R1 _ (CR_of_Q R1 (r-q))). - apply (CRmorph_increasing_inv _ _ f). - apply (CRlt_le_trans R2 _ (CR_of_Q R2 (r - q))). - apply (CRplus_lt_reg_r R2 (CR_of_Q R2 q)). - apply (CRlt_le_trans R2 _ _ _ H). - 2: apply CRmorph_rat. - apply (CRle_trans R2 _ (CR_of_Q R2 (r-q+q))). - intro abs. apply lt_CR_of_Q in abs. ring_simplify in abs. - exact (Qlt_not_le _ _ abs (Qle_refl _)). - destruct (CR_of_Q_plus R2 (r-q) q). exact H1. - apply (CRle_trans R1 _ (CRplus R1 (CR_of_Q R1 r) (CR_of_Q R1 (-q)))). - destruct (CR_of_Q_plus R1 r (-q)). exact H1. - apply CRplus_le_compat_l. destruct (CR_of_Q_opp R1 q). exact H1. -Qed. - -Lemma CRmorph_plus : forall (R1 R2 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2) - (x y : CRcarrier R1), - orderEq _ (CRlt R2) (CRmorph _ _ f (CRplus R1 x y)) - (CRplus R2 (CRmorph _ _ f x) (CRmorph _ _ f y)). -Proof. - intros R1 R2 f. - assert (forall (x y : CRcarrier R1), - orderLe _ (CRlt R2) (CRplus R2 (CRmorph R1 R2 f x) (CRmorph R1 R2 f y)) - (CRmorph R1 R2 f (CRplus R1 x y))). - { intros x y abs. destruct (CR_Q_dense R2 _ _ abs) as [r [H H0]]. clear abs. - destruct (CRmorph_rat _ _ f r) as [H1 _]. - apply (CRlt_le_trans R2 _ _ _ H) in H1. clear H. - apply CRmorph_increasing_inv in H1. - apply (CRlt_asym R1 _ _ H1). clear H1. - destruct (CR_Q_dense R2 _ _ H0) as [q [H2 H3]]. - apply lt_CR_of_Q in H2. - assert (Qlt (r-q) 0) as epsNeg. - { apply (Qplus_lt_r _ _ q). ring_simplify. exact H2. } - destruct (CR_Q_dense R1 _ _ (CRplus_neg_rat_lt R1 x (r-q) epsNeg)) - as [s [H4 H5]]. - apply (CRlt_trans R1 _ (CRplus R1 (CR_of_Q R1 s) y)). - 2: apply CRplus_lt_compat_r, H5. - apply (CRmorph_increasing_inv _ _ f). - apply (CRlt_le_trans R2 _ (CRplus R2 (CR_of_Q R2 s) (CRmorph _ _ f y))). - apply (CRmorph_increasing _ _ f) in H4. - destruct (CRmorph_plus_rat _ _ f x (r-q)) as [H _]. - apply (CRle_lt_trans R2 _ _ _ H) in H4. clear H. - destruct (CRmorph_rat _ _ f s) as [_ H1]. - apply (CRlt_le_trans R2 _ _ _ H4) in H1. clear H4. - apply (CRlt_trans R2 _ (CRplus R2 (CRplus R2 (CRmorph R1 R2 f x) (CR_of_Q R2 (r - q))) - (CRmorph R1 R2 f y))). - 2: apply CRplus_lt_compat_r, H1. - apply (CRlt_le_trans R2 _ (CRplus R2 (CRplus R2 (CR_of_Q R2 (r - q)) (CRmorph R1 R2 f x)) - (CRmorph R1 R2 f y))). - apply (CRlt_le_trans R2 _ (CRplus R2 (CR_of_Q R2 (r - q)) - (CRplus R2 (CRmorph R1 R2 f x) (CRmorph R1 R2 f y)))). - apply (CRle_lt_trans R2 _ (CRplus R2 (CR_of_Q R2 (r - q)) (CR_of_Q R2 q))). - 2: apply CRplus_lt_compat_l, H3. - intro abs. - destruct (CR_of_Q_plus R2 (r-q) q) as [_ H4]. - apply (CRle_lt_trans R2 _ _ _ H4) in abs. clear H4. - destruct (CRmorph_rat _ _ f r) as [_ H4]. - apply (CRlt_le_trans R2 _ _ _ abs) in H4. clear abs. - apply lt_CR_of_Q in H4. ring_simplify in H4. - exact (Qlt_not_le _ _ H4 (Qle_refl _)). - destruct (CRisRing R2); apply Radd_assoc. - apply CRplus_le_compat_r. destruct (CRisRing R2). - destruct (Radd_comm (CRmorph R1 R2 f x) (CR_of_Q R2 (r - q))). - exact H. - intro abs. - destruct (CRmorph_plus_rat _ _ f y s) as [H _]. apply H. clear H. - apply (CRlt_le_trans R2 _ (CRplus R2 (CR_of_Q R2 s) (CRmorph R1 R2 f y))). - apply (CRle_lt_trans R2 _ (CRmorph R1 R2 f (CRplus R1 (CR_of_Q R1 s) y))). - apply CRmorph_proper. destruct (CRisRing R1); apply Radd_comm. - exact abs. destruct (CRisRing R2); apply Radd_comm. } - split. - - apply H. - - specialize (H (CRplus R1 x y) (CRopp R1 y)). - intro abs. apply H. clear H. - apply (CRle_lt_trans R2 _ (CRmorph R1 R2 f x)). - apply CRmorph_proper. destruct (CRisRing R1). - apply (CReq_trans R1 _ (CRplus R1 x (CRplus R1 y (CRopp R1 y)))). - apply CReq_sym, Radd_assoc. - apply (CReq_trans R1 _ (CRplus R1 x (CRzero R1))). 2: apply CRplus_0_r. - destruct (CRisRingExt R1). apply Radd_ext. - apply CReq_refl. apply Ropp_def. - apply (CRplus_lt_reg_r R2 (CRmorph R1 R2 f y)). - apply (CRlt_le_trans R2 _ _ _ abs). clear abs. - apply (CRle_trans R2 _ (CRplus R2 (CRmorph R1 R2 f (CRplus R1 x y)) (CRzero R2))). - destruct (CRplus_0_r R2 (CRmorph R1 R2 f (CRplus R1 x y))). exact H. - apply (CRle_trans R2 _ (CRplus R2 (CRmorph R1 R2 f (CRplus R1 x y)) - (CRplus R2 (CRmorph R1 R2 f (CRopp R1 y)) (CRmorph R1 R2 f y)))). - apply CRplus_le_compat_l. - apply (CRle_trans R2 _ (CRplus R2 (CRopp R2 (CRmorph R1 R2 f y)) (CRmorph R1 R2 f y))). - destruct (CRplus_opp_l R2 (CRmorph R1 R2 f y)). exact H. - apply CRplus_le_compat_r. destruct (CRmorph_opp _ _ f y). exact H. - destruct (CRisRing R2). - destruct (Radd_assoc (CRmorph R1 R2 f (CRplus R1 x y)) - (CRmorph R1 R2 f (CRopp R1 y)) (CRmorph R1 R2 f y)). - exact H0. -Qed. - -Lemma CRmorph_mult_pos : forall (R1 R2 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2) - (x : CRcarrier R1) (n : nat), - orderEq _ (CRlt R2) (CRmorph _ _ f (CRmult R1 x (CR_of_Q R1 (Z.of_nat n # 1)))) - (CRmult R2 (CRmorph _ _ f x) (CR_of_Q R2 (Z.of_nat n # 1))). -Proof. - induction n. - - simpl. destruct (CRisRingExt R1). - apply (CReq_trans R2 _ (CRzero R2)). - + apply (CReq_trans R2 _ (CRmorph R1 R2 f (CRzero R1))). - 2: apply CRmorph_zero. apply CRmorph_proper. - apply (CReq_trans R1 _ (CRmult R1 x (CRzero R1))). - 2: apply CRmult_0_r. apply Rmul_ext. apply CReq_refl. apply CR_of_Q_zero. - + apply (CReq_trans R2 _ (CRmult R2 (CRmorph R1 R2 f x) (CRzero R2))). - apply CReq_sym, CRmult_0_r. destruct (CRisRingExt R2). - apply Rmul_ext0. apply CReq_refl. apply CReq_sym, CR_of_Q_zero. - - destruct (CRisRingExt R1), (CRisRingExt R2). - apply (CReq_trans - R2 _ (CRmorph R1 R2 f (CRplus R1 x (CRmult R1 x (CR_of_Q R1 (Z.of_nat n # 1)))))). - apply CRmorph_proper. - apply (CReq_trans R1 _ (CRmult R1 x (CRplus R1 (CRone R1) (CR_of_Q R1 (Z.of_nat n # 1))))). - apply Rmul_ext. apply CReq_refl. - apply (CReq_trans R1 _ (CR_of_Q R1 (1 + (Z.of_nat n # 1)))). - apply CR_of_Q_proper. rewrite Nat2Z.inj_succ. unfold Z.succ. - rewrite Z.add_comm. rewrite Qinv_plus_distr. reflexivity. - apply (CReq_trans R1 _ (CRplus R1 (CR_of_Q R1 1) (CR_of_Q R1 (Z.of_nat n # 1)))). - apply CR_of_Q_plus. apply Radd_ext. apply CR_of_Q_one. apply CReq_refl. - apply (CReq_trans R1 _ (CRplus R1 (CRmult R1 x (CRone R1)) - (CRmult R1 x (CR_of_Q R1 (Z.of_nat n # 1))))). - apply CRmult_plus_distr_l. apply Radd_ext. apply CRmult_1_r. apply CReq_refl. - apply (CReq_trans R2 _ (CRplus R2 (CRmorph R1 R2 f x) - (CRmorph R1 R2 f (CRmult R1 x (CR_of_Q R1 (Z.of_nat n # 1)))))). - apply CRmorph_plus. - apply (CReq_trans R2 _ (CRplus R2 (CRmorph R1 R2 f x) - (CRmult R2 (CRmorph R1 R2 f x) (CR_of_Q R2 (Z.of_nat n # 1))))). - apply Radd_ext0. apply CReq_refl. exact IHn. - apply (CReq_trans R2 _ (CRmult R2 (CRmorph R1 R2 f x) (CRplus R2 (CRone R2) (CR_of_Q R2 (Z.of_nat n # 1))))). - apply (CReq_trans R2 _ (CRplus R2 (CRmult R2 (CRmorph R1 R2 f x) (CRone R2)) - (CRmult R2 (CRmorph _ _ f x) (CR_of_Q R2 (Z.of_nat n # 1))))). - apply Radd_ext0. 2: apply CReq_refl. apply CReq_sym, CRmult_1_r. - apply CReq_sym, CRmult_plus_distr_l. - apply Rmul_ext0. apply CReq_refl. - apply (CReq_trans R2 _ (CR_of_Q R2 (1 + (Z.of_nat n # 1)))). - apply (CReq_trans R2 _ (CRplus R2 (CR_of_Q R2 1) (CR_of_Q R2 (Z.of_nat n # 1)))). - apply Radd_ext0. apply CReq_sym, CR_of_Q_one. apply CReq_refl. - apply CReq_sym, CR_of_Q_plus. - apply CR_of_Q_proper. rewrite Nat2Z.inj_succ. unfold Z.succ. - rewrite Z.add_comm. rewrite Qinv_plus_distr. reflexivity. -Qed. - -Lemma NatOfZ : forall n : Z, { p : nat | n = Z.of_nat p \/ n = Z.opp (Z.of_nat p) }. -Proof. - intros [|p|n]. - - exists O. left. reflexivity. - - exists (Pos.to_nat p). left. rewrite positive_nat_Z. reflexivity. - - exists (Pos.to_nat n). right. rewrite positive_nat_Z. reflexivity. -Qed. - -Lemma CRmorph_mult_int : forall (R1 R2 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2) - (x : CRcarrier R1) (n : Z), - orderEq _ (CRlt R2) (CRmorph _ _ f (CRmult R1 x (CR_of_Q R1 (n # 1)))) - (CRmult R2 (CRmorph _ _ f x) (CR_of_Q R2 (n # 1))). -Proof. - intros. destruct (NatOfZ n) as [p [pos|neg]]. - - subst n. apply CRmorph_mult_pos. - - subst n. - apply (CReq_trans R2 _ (CRopp R2 (CRmorph R1 R2 f (CRmult R1 x (CR_of_Q R1 (Z.of_nat p # 1)))))). - + apply (CReq_trans R2 _ (CRmorph R1 R2 f (CRopp R1 (CRmult R1 x (CR_of_Q R1 (Z.of_nat p # 1)))))). - 2: apply CRmorph_opp. apply CRmorph_proper. - apply (CReq_trans R1 _ (CRmult R1 x (CR_of_Q R1 (- (Z.of_nat p # 1))))). - destruct (CRisRingExt R1). apply Rmul_ext. apply CReq_refl. - apply CR_of_Q_proper. reflexivity. - apply (CReq_trans R1 _ (CRmult R1 x (CRopp R1 (CR_of_Q R1 (Z.of_nat p # 1))))). - destruct (CRisRingExt R1). apply Rmul_ext. apply CReq_refl. - apply CR_of_Q_opp. apply CReq_sym, CRopp_mult_distr_r. - + apply (CReq_trans R2 _ (CRopp R2 (CRmult R2 (CRmorph R1 R2 f x) (CR_of_Q R2 (Z.of_nat p # 1))))). - destruct (CRisRingExt R2). apply Ropp_ext. apply CRmorph_mult_pos. - apply (CReq_trans R2 _ (CRmult R2 (CRmorph R1 R2 f x) (CRopp R2 (CR_of_Q R2 (Z.of_nat p # 1))))). - apply CRopp_mult_distr_r. destruct (CRisRingExt R2). - apply Rmul_ext. apply CReq_refl. - apply (CReq_trans R2 _ (CR_of_Q R2 (- (Z.of_nat p # 1)))). - apply CReq_sym, CR_of_Q_opp. apply CR_of_Q_proper. reflexivity. -Qed. - -Lemma CRmorph_mult_inv : forall (R1 R2 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2) - (x : CRcarrier R1) (p : positive), - orderEq _ (CRlt R2) (CRmorph _ _ f (CRmult R1 x (CR_of_Q R1 (1 # p)))) - (CRmult R2 (CRmorph _ _ f x) (CR_of_Q R2 (1 # p))). -Proof. - intros. apply (CRmult_eq_reg_r R2 (CR_of_Q R2 (Z.pos p # 1))). - left. apply (CRle_lt_trans R2 _ (CR_of_Q R2 0)). - apply CR_of_Q_zero. apply CR_of_Q_lt. reflexivity. - apply (CReq_trans R2 _ (CRmorph _ _ f x)). - - apply (CReq_trans - R2 _ (CRmorph R1 R2 f (CRmult R1 (CRmult R1 x (CR_of_Q R1 (1 # p))) - (CR_of_Q R1 (Z.pos p # 1))))). - apply CReq_sym, CRmorph_mult_int. apply CRmorph_proper. - apply (CReq_trans - R1 _ (CRmult R1 x (CRmult R1 (CR_of_Q R1 (1 # p)) - (CR_of_Q R1 (Z.pos p # 1))))). - destruct (CRisRing R1). apply CReq_sym, Rmul_assoc. - apply (CReq_trans R1 _ (CRmult R1 x (CRone R1))). - apply (Rmul_ext (CRisRingExt R1)). apply CReq_refl. - apply (CReq_trans R1 _ (CR_of_Q R1 ((1#p) * (Z.pos p # 1)))). - apply CReq_sym, CR_of_Q_mult. - apply (CReq_trans R1 _ (CR_of_Q R1 1)). - apply CR_of_Q_proper. reflexivity. apply CR_of_Q_one. - apply CRmult_1_r. - - apply (CReq_trans R2 _ (CRmult R2 (CRmorph R1 R2 f x) - (CRmult R2 (CR_of_Q R2 (1 # p)) (CR_of_Q R2 (Z.pos p # 1))))). - 2: apply (Rmul_assoc (CRisRing R2)). - apply (CReq_trans R2 _ (CRmult R2 (CRmorph R1 R2 f x) (CRone R2))). - apply CReq_sym, CRmult_1_r. - apply (Rmul_ext (CRisRingExt R2)). apply CReq_refl. - apply (CReq_trans R2 _ (CR_of_Q R2 1)). - apply CReq_sym, CR_of_Q_one. - apply (CReq_trans R2 _ (CR_of_Q R2 ((1#p)*(Z.pos p # 1)))). - apply CR_of_Q_proper. reflexivity. apply CR_of_Q_mult. -Qed. - -Lemma CRmorph_mult_rat : forall (R1 R2 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2) - (x : CRcarrier R1) (q : Q), - orderEq _ (CRlt R2) (CRmorph _ _ f (CRmult R1 x (CR_of_Q R1 q))) - (CRmult R2 (CRmorph _ _ f x) (CR_of_Q R2 q)). -Proof. - intros. destruct q as [a b]. - apply (CReq_trans R2 _ (CRmult R2 (CRmorph _ _ f (CRmult R1 x (CR_of_Q R1 (a # 1)))) - (CR_of_Q R2 (1 # b)))). - - apply (CReq_trans - R2 _ (CRmorph R1 R2 f (CRmult R1 (CRmult R1 x (CR_of_Q R1 (a # 1))) - (CR_of_Q R1 (1 # b))))). - 2: apply CRmorph_mult_inv. apply CRmorph_proper. - apply (CReq_trans R1 _ (CRmult R1 x (CRmult R1 (CR_of_Q R1 (a # 1)) - (CR_of_Q R1 (1 # b))))). - apply (Rmul_ext (CRisRingExt R1)). apply CReq_refl. - apply (CReq_trans R1 _ (CR_of_Q R1 ((a#1)*(1#b)))). - apply CR_of_Q_proper. unfold Qeq; simpl. rewrite Z.mul_1_r. reflexivity. - apply CR_of_Q_mult. - apply (Rmul_assoc (CRisRing R1)). - - apply (CReq_trans R2 _ (CRmult R2 (CRmult R2 (CRmorph _ _ f x) (CR_of_Q R2 (a # 1))) - (CR_of_Q R2 (1 # b)))). - apply (Rmul_ext (CRisRingExt R2)). apply CRmorph_mult_int. - apply CReq_refl. - apply (CReq_trans R2 _ (CRmult R2 (CRmorph R1 R2 f x) - (CRmult R2 (CR_of_Q R2 (a # 1)) (CR_of_Q R2 (1 # b))))). - apply CReq_sym, (Rmul_assoc (CRisRing R2)). - apply (Rmul_ext (CRisRingExt R2)). apply CReq_refl. - apply (CReq_trans R2 _ (CR_of_Q R2 ((a#1)*(1#b)))). - apply CReq_sym, CR_of_Q_mult. - apply CR_of_Q_proper. unfold Qeq; simpl. rewrite Z.mul_1_r. reflexivity. -Qed. - -Lemma CRmorph_mult_pos_pos_le : forall (R1 R2 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2) - (x y : CRcarrier R1), - CRlt R1 (CRzero R1) y - -> orderLe _ (CRlt R2) (CRmult R2 (CRmorph _ _ f x) (CRmorph _ _ f y)) - (CRmorph _ _ f (CRmult R1 x y)). -Proof. - intros. intro abs. destruct (CR_Q_dense R2 _ _ abs) as [q [H1 H2]]. - destruct (CRmorph_rat _ _ f q) as [H3 _]. - apply (CRlt_le_trans R2 _ _ _ H1) in H3. clear H1. - apply CRmorph_increasing_inv in H3. - apply (CRlt_asym R1 _ _ H3). clear H3. - destruct (CR_Q_dense R2 _ _ H2) as [r [H1 H3]]. - apply lt_CR_of_Q in H1. - destruct (CR_archimedean R1 y) as [A Amaj]. - assert (/ ((r - q) * (1 # A)) * (q - r) == - (Z.pos A # 1)) as diveq. - { rewrite Qinv_mult_distr. setoid_replace (q-r) with (-1*(r-q)). - field_simplify. reflexivity. 2: field. - split. intro H4. inversion H4. intro H4. - apply Qlt_minus_iff in H1. rewrite H4 in H1. inversion H1. } - destruct (CR_Q_dense R1 (CRplus R1 x (CR_of_Q R1 ((q-r) * (1#A)))) x) - as [s [H4 H5]]. - - apply (CRlt_le_trans R1 _ (CRplus R1 x (CRzero R1))). - 2: apply CRplus_0_r. apply CRplus_lt_compat_l. - apply (CRplus_lt_reg_l R1 (CR_of_Q R1 ((r-q) * (1#A)))). - apply (CRle_lt_trans R1 _ (CRzero R1)). - apply (CRle_trans R1 _ (CR_of_Q R1 ((r-q)*(1#A) + (q-r)*(1#A)))). - destruct (CR_of_Q_plus R1 ((r-q)*(1#A)) ((q-r)*(1#A))). - exact H0. apply (CRle_trans R1 _ (CR_of_Q R1 0)). - 2: destruct (CR_of_Q_zero R1); exact H4. - intro H4. apply lt_CR_of_Q in H4. ring_simplify in H4. - inversion H4. - apply (CRlt_le_trans R1 _ (CR_of_Q R1 ((r - q) * (1 # A)))). - 2: apply CRplus_0_r. - apply (CRle_lt_trans R1 _ (CR_of_Q R1 0)). - apply CR_of_Q_zero. apply CR_of_Q_lt. - rewrite <- (Qmult_0_r (r-q)). apply Qmult_lt_l. - apply Qlt_minus_iff in H1. exact H1. reflexivity. - - apply (CRmorph_increasing _ _ f) in H4. - destruct (CRmorph_plus _ _ f x (CR_of_Q R1 ((q-r) * (1#A)))) as [H6 _]. - apply (CRle_lt_trans R2 _ _ _ H6) in H4. clear H6. - destruct (CRmorph_rat _ _ f s) as [_ H6]. - apply (CRlt_le_trans R2 _ _ _ H4) in H6. clear H4. - apply (CRmult_lt_compat_r R2 (CRmorph _ _ f y)) in H6. - destruct (Rdistr_l (CRisRing R2) (CRmorph _ _ f x) - (CRmorph R1 R2 f (CR_of_Q R1 ((q-r) * (1#A)))) - (CRmorph _ _ f y)) as [H4 _]. - apply (CRle_lt_trans R2 _ _ _ H4) in H6. clear H4. - apply (CRle_lt_trans R1 _ (CRmult R1 (CR_of_Q R1 s) y)). - 2: apply CRmult_lt_compat_r. 2: exact H. 2: exact H5. - apply (CRmorph_le_inv _ _ f). - apply (CRle_trans R2 _ (CR_of_Q R2 q)). - destruct (CRmorph_rat _ _ f q). exact H4. - apply (CRle_trans R2 _ (CRmult R2 (CR_of_Q R2 s) (CRmorph _ _ f y))). - apply (CRle_trans R2 _ (CRplus R2 (CRmult R2 (CRmorph _ _ f x) (CRmorph _ _ f y)) - (CR_of_Q R2 (q-r)))). - apply (CRle_trans R2 _ (CRplus R2 (CR_of_Q R2 r) (CR_of_Q R2 (q - r)))). - + apply (CRle_trans R2 _ (CR_of_Q R2 (r + (q-r)))). - intro H4. apply lt_CR_of_Q in H4. ring_simplify in H4. - exact (Qlt_not_le q q H4 (Qle_refl q)). - destruct (CR_of_Q_plus R2 r (q-r)). exact H4. - + apply CRplus_le_compat_r. intro H4. - apply (CRlt_asym R2 _ _ H3). exact H4. - + intro H4. apply (CRlt_asym R2 _ _ H4). clear H4. - apply (CRlt_trans_flip R2 _ _ _ H6). clear H6. - apply CRplus_lt_compat_l. - apply (CRlt_le_trans R2 _ (CRmult R2 (CR_of_Q R2 ((q - r) * (1 # A))) (CRmorph R1 R2 f y))). - apply (CRmult_lt_reg_l R2 (CR_of_Q R2 (/((r-q)*(1#A))))). - apply (CRle_lt_trans R2 _ (CR_of_Q R2 0)). apply CR_of_Q_zero. - apply CR_of_Q_lt, Qinv_lt_0_compat. - rewrite <- (Qmult_0_r (r-q)). apply Qmult_lt_l. - apply Qlt_minus_iff in H1. exact H1. reflexivity. - apply (CRle_lt_trans R2 _ (CRopp R2 (CR_of_Q R2 (Z.pos A # 1)))). - apply (CRle_trans R2 _ (CR_of_Q R2 (-(Z.pos A # 1)))). - apply (CRle_trans R2 _ (CR_of_Q R2 ((/ ((r - q) * (1 # A))) * (q - r)))). - destruct (CR_of_Q_mult R2 (/ ((r - q) * (1 # A))) (q - r)). - exact H0. destruct (CR_of_Q_proper R2 (/ ((r - q) * (1 # A)) * (q - r)) - (-(Z.pos A # 1))). - exact diveq. intro H7. apply lt_CR_of_Q in H7. - rewrite diveq in H7. exact (Qlt_not_le _ _ H7 (Qle_refl _)). - destruct (CR_of_Q_opp R2 (Z.pos A # 1)). exact H4. - apply (CRlt_le_trans R2 _ (CRopp R2 (CRmorph _ _ f y))). - apply CRopp_gt_lt_contravar. - apply (CRlt_le_trans R2 _ (CRmorph _ _ f (CR_of_Q R1 (Z.pos A # 1)))). - apply CRmorph_increasing. exact Amaj. - destruct (CRmorph_rat _ _ f (Z.pos A # 1)). exact H4. - apply (CRle_trans R2 _ (CRmult R2 (CRopp R2 (CRone R2)) (CRmorph _ _ f y))). - apply (CRle_trans R2 _ (CRopp R2 (CRmult R2 (CRone R2) (CRmorph R1 R2 f y)))). - destruct (Ropp_ext (CRisRingExt R2) (CRmorph _ _ f y) - (CRmult R2 (CRone R2) (CRmorph R1 R2 f y))). - apply CReq_sym, (Rmul_1_l (CRisRing R2)). exact H4. - destruct (CRopp_mult_distr_l R2 (CRone R2) (CRmorph _ _ f y)). exact H4. - apply (CRle_trans R2 _ (CRmult R2 (CRmult R2 (CR_of_Q R2 (/ ((r - q) * (1 # A)))) - (CR_of_Q R2 ((q - r) * (1 # A)))) - (CRmorph R1 R2 f y))). - apply CRmult_le_compat_r. - apply (CRle_lt_trans R2 _ (CRmorph _ _ f (CRzero R1))). - apply CRmorph_zero. apply CRmorph_increasing. exact H. - apply (CRle_trans R2 _ (CR_of_Q R2 ((/ ((r - q) * (1 # A))) - * ((q - r) * (1 # A))))). - apply (CRle_trans R2 _ (CR_of_Q R2 (-1))). - apply (CRle_trans R2 _ (CRopp R2 (CR_of_Q R2 1))). - destruct (Ropp_ext (CRisRingExt R2) (CRone R2) (CR_of_Q R2 1)). - apply CReq_sym, CR_of_Q_one. exact H4. - destruct (CR_of_Q_opp R2 1). exact H0. - destruct (CR_of_Q_proper R2 (-1) (/ ((r - q) * (1 # A)) * ((q - r) * (1 # A)))). - field. split. - intro H4. inversion H4. intro H4. apply Qlt_minus_iff in H1. - rewrite H4 in H1. inversion H1. exact H4. - destruct (CR_of_Q_mult R2 (/ ((r - q) * (1 # A))) ((q - r) * (1 # A))). - exact H4. - destruct (Rmul_assoc (CRisRing R2) (CR_of_Q R2 (/ ((r - q) * (1 # A)))) - (CR_of_Q R2 ((q - r) * (1 # A))) - (CRmorph R1 R2 f y)). - exact H0. - apply CRmult_le_compat_r. - apply (CRle_lt_trans R2 _ (CRmorph _ _ f (CRzero R1))). - apply CRmorph_zero. apply CRmorph_increasing. exact H. - destruct (CRmorph_rat _ _ f ((q - r) * (1 # A))). exact H0. - + apply (CRle_trans R2 _ (CRmorph _ _ f (CRmult R1 y (CR_of_Q R1 s)))). - apply (CRle_trans R2 _ (CRmult R2 (CRmorph R1 R2 f y) (CR_of_Q R2 s))). - destruct (Rmul_comm (CRisRing R2) (CRmorph R1 R2 f y) (CR_of_Q R2 s)). - exact H0. - destruct (CRmorph_mult_rat _ _ f y s). exact H0. - destruct (CRmorph_proper _ _ f (CRmult R1 y (CR_of_Q R1 s)) - (CRmult R1 (CR_of_Q R1 s) y)). - apply (Rmul_comm (CRisRing R1)). exact H4. - + apply (CRle_lt_trans R2 _ (CRmorph _ _ f (CRzero R1))). - apply CRmorph_zero. apply CRmorph_increasing. exact H. -Qed. - -Lemma CRmorph_mult_pos_pos : forall (R1 R2 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2) - (x y : CRcarrier R1), - CRlt R1 (CRzero R1) y - -> orderEq _ (CRlt R2) (CRmorph _ _ f (CRmult R1 x y)) - (CRmult R2 (CRmorph _ _ f x) (CRmorph _ _ f y)). -Proof. - split. apply CRmorph_mult_pos_pos_le. exact H. - intro abs. destruct (CR_Q_dense R2 _ _ abs) as [q [H1 H2]]. - destruct (CRmorph_rat _ _ f q) as [_ H3]. - apply (CRle_lt_trans R2 _ _ _ H3) in H2. clear H3. - apply CRmorph_increasing_inv in H2. - apply (CRlt_asym R1 _ _ H2). clear H2. - destruct (CR_Q_dense R2 _ _ H1) as [r [H2 H3]]. - apply lt_CR_of_Q in H3. - destruct (CR_archimedean R1 y) as [A Amaj]. - destruct (CR_Q_dense R1 x (CRplus R1 x (CR_of_Q R1 ((q-r) * (1#A))))) - as [s [H4 H5]]. - - apply (CRle_lt_trans R1 _ (CRplus R1 x (CRzero R1))). - apply CRplus_0_r. apply CRplus_lt_compat_l. - apply (CRle_lt_trans R1 _ (CR_of_Q R1 0)). - apply CR_of_Q_zero. apply CR_of_Q_lt. - rewrite <- (Qmult_0_r (q-r)). apply Qmult_lt_l. - apply Qlt_minus_iff in H3. exact H3. reflexivity. - - apply (CRmorph_increasing _ _ f) in H5. - destruct (CRmorph_plus _ _ f x (CR_of_Q R1 ((q-r) * (1#A)))) as [_ H6]. - apply (CRlt_le_trans R2 _ _ _ H5) in H6. clear H5. - destruct (CRmorph_rat _ _ f s) as [H5 _ ]. - apply (CRle_lt_trans R2 _ _ _ H5) in H6. clear H5. - apply (CRmult_lt_compat_r R2 (CRmorph _ _ f y)) in H6. - apply (CRlt_le_trans R1 _ (CRmult R1 (CR_of_Q R1 s) y)). - apply CRmult_lt_compat_r. exact H. exact H4. clear H4. - apply (CRmorph_le_inv _ _ f). - apply (CRle_trans R2 _ (CR_of_Q R2 q)). - 2: destruct (CRmorph_rat _ _ f q); exact H0. - apply (CRle_trans R2 _ (CRmult R2 (CR_of_Q R2 s) (CRmorph R1 R2 f y))). - + apply (CRle_trans R2 _ (CRmorph _ _ f (CRmult R1 y (CR_of_Q R1 s)))). - destruct (CRmorph_proper _ _ f (CRmult R1 (CR_of_Q R1 s) y) - (CRmult R1 y (CR_of_Q R1 s))). - apply (Rmul_comm (CRisRing R1)). exact H4. - apply (CRle_trans R2 _ (CRmult R2 (CRmorph R1 R2 f y) (CR_of_Q R2 s))). - exact (proj2 (CRmorph_mult_rat _ _ f y s)). - destruct (Rmul_comm (CRisRing R2) (CR_of_Q R2 s) (CRmorph R1 R2 f y)). - exact H0. - + intro H5. apply (CRlt_asym R2 _ _ H5). clear H5. - apply (CRlt_trans R2 _ _ _ H6). clear H6. - apply (CRle_lt_trans - R2 _ (CRplus R2 - (CRmult R2 (CRmorph _ _ f x) (CRmorph _ _ f y)) - (CRmult R2 (CRmorph R1 R2 f (CR_of_Q R1 ((q - r) * (1 # A)))) - (CRmorph R1 R2 f y)))). - apply (Rdistr_l (CRisRing R2)). - apply (CRle_lt_trans - R2 _ (CRplus R2 (CR_of_Q R2 r) - (CRmult R2 (CRmorph R1 R2 f (CR_of_Q R1 ((q - r) * (1 # A)))) - (CRmorph R1 R2 f y)))). - apply CRplus_le_compat_r. intro H5. apply (CRlt_asym R2 _ _ H5 H2). - clear H2. - apply (CRle_lt_trans - R2 _ (CRplus R2 (CR_of_Q R2 r) - (CRmult R2 (CR_of_Q R2 ((q - r) * (1 # A))) - (CRmorph R1 R2 f y)))). - apply CRplus_le_compat_l, CRmult_le_compat_r. - apply (CRle_lt_trans R2 _ (CRmorph _ _ f (CRzero R1))). - apply CRmorph_zero. apply CRmorph_increasing. exact H. - destruct (CRmorph_rat _ _ f ((q - r) * (1 # A))). exact H2. - apply (CRlt_le_trans R2 _ (CRplus R2 (CR_of_Q R2 r) - (CR_of_Q R2 ((q - r))))). - apply CRplus_lt_compat_l. - * apply (CRmult_lt_reg_l R2 (CR_of_Q R2 (/((q - r) * (1 # A))))). - apply (CRle_lt_trans R2 _ (CR_of_Q R2 0)). apply CR_of_Q_zero. - apply CR_of_Q_lt, Qinv_lt_0_compat. - rewrite <- (Qmult_0_r (q-r)). apply Qmult_lt_l. - apply Qlt_minus_iff in H3. exact H3. reflexivity. - apply (CRle_lt_trans R2 _ (CRmorph _ _ f y)). - apply (CRle_trans R2 _ (CRmult R2 (CRmult R2 (CR_of_Q R2 (/ ((q - r) * (1 # A)))) - (CR_of_Q R2 ((q - r) * (1 # A)))) - (CRmorph R1 R2 f y))). - exact (proj2 (Rmul_assoc (CRisRing R2) (CR_of_Q R2 (/ ((q - r) * (1 # A)))) - (CR_of_Q R2 ((q - r) * (1 # A))) - (CRmorph _ _ f y))). - apply (CRle_trans R2 _ (CRmult R2 (CRone R2) (CRmorph R1 R2 f y))). - apply CRmult_le_compat_r. - apply (CRle_lt_trans R2 _ (CRmorph _ _ f (CRzero R1))). - apply CRmorph_zero. apply CRmorph_increasing. exact H. - apply (CRle_trans R2 _ (CR_of_Q R2 ((/ ((q - r) * (1 # A))) * ((q - r) * (1 # A))))). - exact (proj1 (CR_of_Q_mult R2 (/ ((q - r) * (1 # A))) ((q - r) * (1 # A)))). - apply (CRle_trans R2 _ (CR_of_Q R2 1)). - destruct (CR_of_Q_proper R2 (/ ((q - r) * (1 # A)) * ((q - r) * (1 # A))) 1). - field_simplify. reflexivity. split. - intro H5. inversion H5. intro H5. apply Qlt_minus_iff in H3. - rewrite H5 in H3. inversion H3. exact H2. - destruct (CR_of_Q_one R2). exact H2. - destruct (Rmul_1_l (CRisRing R2) (CRmorph _ _ f y)). - intro H5. contradiction. - apply (CRlt_le_trans R2 _ (CR_of_Q R2 (Z.pos A # 1))). - apply (CRlt_le_trans R2 _ (CRmorph _ _ f (CR_of_Q R1 (Z.pos A # 1)))). - apply CRmorph_increasing. exact Amaj. - exact (proj2 (CRmorph_rat _ _ f (Z.pos A # 1))). - apply (CRle_trans R2 _ (CR_of_Q R2 ((/ ((q - r) * (1 # A))) * (q - r)))). - 2: exact (proj2 (CR_of_Q_mult R2 (/ ((q - r) * (1 # A))) (q - r))). - destruct (CR_of_Q_proper R2 (Z.pos A # 1) (/ ((q - r) * (1 # A)) * (q - r))). - field_simplify. reflexivity. split. - intro H5. inversion H5. intro H5. apply Qlt_minus_iff in H3. - rewrite H5 in H3. inversion H3. exact H2. - * apply (CRle_trans R2 _ (CR_of_Q R2 (r + (q-r)))). - exact (proj1 (CR_of_Q_plus R2 r (q-r))). - destruct (CR_of_Q_proper R2 (r + (q-r)) q). ring. exact H2. - + apply (CRle_lt_trans R2 _ (CRmorph _ _ f (CRzero R1))). - apply CRmorph_zero. apply CRmorph_increasing. exact H. -Qed. - -Lemma CRmorph_mult : forall (R1 R2 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2) - (x y : CRcarrier R1), - orderEq _ (CRlt R2) (CRmorph _ _ f (CRmult R1 x y)) - (CRmult R2 (CRmorph _ _ f x) (CRmorph _ _ f y)). -Proof. - intros. - destruct (CR_archimedean R1 (CRopp R1 y)) as [p pmaj]. - apply (CRplus_eq_reg_r R2 (CRmult R2 (CRmorph _ _ f x) - (CR_of_Q R2 (Z.pos p # 1)))). - apply (CReq_trans R2 _ (CRmorph _ _ f (CRmult R1 x (CRplus R1 y (CR_of_Q R1 (Z.pos p # 1)))))). - - apply (CReq_trans R2 _ (CRplus R2 (CRmorph R1 R2 f (CRmult R1 x y)) - (CRmorph R1 R2 f (CRmult R1 x (CR_of_Q R1 (Z.pos p # 1)))))). - apply (Radd_ext (CRisRingExt R2)). apply CReq_refl. - apply CReq_sym, CRmorph_mult_int. - apply (CReq_trans R2 _ (CRmorph _ _ f (CRplus R1 (CRmult R1 x y) - (CRmult R1 x (CR_of_Q R1 (Z.pos p # 1)))))). - apply CReq_sym, CRmorph_plus. apply CRmorph_proper. - apply CReq_sym, CRmult_plus_distr_l. - - apply (CReq_trans R2 _ (CRmult R2 (CRmorph _ _ f x) - (CRmorph _ _ f (CRplus R1 y (CR_of_Q R1 (Z.pos p # 1)))))). - apply CRmorph_mult_pos_pos. - apply (CRplus_lt_compat_l R1 y) in pmaj. - apply (CRle_lt_trans R1 _ (CRplus R1 y (CRopp R1 y))). - 2: exact pmaj. apply (CRisRing R1). - apply (CReq_trans R2 _ (CRmult R2 (CRmorph R1 R2 f x) - (CRplus R2 (CRmorph R1 R2 f y) (CR_of_Q R2 (Z.pos p # 1))))). - apply (Rmul_ext (CRisRingExt R2)). apply CReq_refl. - apply (CReq_trans R2 _ (CRplus R2 (CRmorph R1 R2 f y) - (CRmorph _ _ f (CR_of_Q R1 (Z.pos p # 1))))). - apply CRmorph_plus. - apply (Radd_ext (CRisRingExt R2)). apply CReq_refl. - apply CRmorph_rat. - apply CRmult_plus_distr_l. -Qed. - -Lemma CRmorph_appart : forall (R1 R2 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2) - (x y : CRcarrier R1) - (app : orderAppart _ (CRlt R1) x y), - orderAppart _ (CRlt R2) (CRmorph _ _ f x) (CRmorph _ _ f y). -Proof. - intros. destruct app. - - left. apply CRmorph_increasing. exact c. - - right. apply CRmorph_increasing. exact c. -Defined. - -Lemma CRmorph_appart_zero : forall (R1 R2 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2) - (x : CRcarrier R1) - (app : orderAppart _ (CRlt R1) x (CRzero R1)), - orderAppart _ (CRlt R2) (CRmorph _ _ f x) (CRzero R2). -Proof. - intros. destruct app. - - left. apply (CRlt_le_trans R2 _ (CRmorph _ _ f (CRzero R1))). - apply CRmorph_increasing. exact c. - exact (proj2 (CRmorph_zero _ _ f)). - - right. apply (CRle_lt_trans R2 _ (CRmorph _ _ f (CRzero R1))). - exact (proj1 (CRmorph_zero _ _ f)). - apply CRmorph_increasing. exact c. -Defined. - -Lemma CRmorph_inv : forall (R1 R2 : ConstructiveReals) - (f : ConstructiveRealsMorphism R1 R2) - (x : CRcarrier R1) - (xnz : orderAppart _ (CRlt R1) x (CRzero R1)) - (fxnz : orderAppart _ (CRlt R2) (CRmorph _ _ f x) (CRzero R2)), - orderEq _ (CRlt R2) (CRmorph _ _ f (CRinv R1 x xnz)) - (CRinv R2 (CRmorph _ _ f x) fxnz). -Proof. - intros. apply (CRmult_eq_reg_r R2 (CRmorph _ _ f x)). - destruct fxnz. right. exact c. left. exact c. - apply (CReq_trans R2 _ (CRone R2)). - 2: apply CReq_sym, CRinv_l. - apply (CReq_trans R2 _ (CRmorph _ _ f (CRmult R1 (CRinv R1 x xnz) x))). - apply CReq_sym, CRmorph_mult. - apply (CReq_trans R2 _ (CRmorph _ _ f (CRone R1))). - apply CRmorph_proper. apply CRinv_l. - apply CRmorph_one. -Qed. - -Definition CauchyMorph (R : ConstructiveReals) - : CReal -> CRcarrier R. -Proof. - intros [xn xcau]. - destruct (CR_complete R (fun n:nat => CR_of_Q R (xn n))). - - intros p. exists (Pos.to_nat p). intros. - specialize (xcau p i j H H0). apply Qlt_le_weak in xcau. - rewrite Qabs_Qle_condition in xcau. split. - + unfold CRminus. - apply (CRle_trans R _ (CRplus R (CR_of_Q R (xn i)) (CR_of_Q R (-xn j)))). - apply (CRle_trans R _ (CR_of_Q R (xn i-xn j))). - apply CR_of_Q_le. apply xcau. exact (proj2 (CR_of_Q_plus R _ _)). - apply CRplus_le_compat_l. exact (proj2 (CR_of_Q_opp R (xn j))). - + unfold CRminus. - apply (CRle_trans R _ (CRplus R (CR_of_Q R (xn i)) (CR_of_Q R (-xn j)))). - apply CRplus_le_compat_l. exact (proj1 (CR_of_Q_opp R (xn j))). - apply (CRle_trans R _ (CR_of_Q R (xn i-xn j))). - exact (proj1 (CR_of_Q_plus R _ _)). - apply CR_of_Q_le. apply xcau. - - exact x. -Defined. - -Lemma CauchyMorph_rat : forall (R : ConstructiveReals) (q : Q), - orderEq _ (CRlt R) (CauchyMorph R (inject_Q q)) (CR_of_Q R q). -Proof. - intros. - unfold CauchyMorph; simpl; - destruct (CRltLinear R), p, (CR_complete R (fun _ : nat => CR_of_Q R q)). - apply CR_cv_const in c0. apply CReq_sym. exact c0. -Qed. - -Lemma CauchyMorph_increasing_Ql : forall (R : ConstructiveReals) (x : CReal) (q : Q), - CRealLt x (inject_Q q) -> CRlt R (CauchyMorph R x) (CR_of_Q R q). -Proof. - intros. - unfold CauchyMorph; simpl; - destruct x as [xn xcau], (CRltLinear R), p, (CR_complete R (fun n : nat => CR_of_Q R (xn n))). - destruct (CRealQ_dense _ _ H) as [r [H0 H1]]. - apply lt_inject_Q in H1. - destruct (s _ x _ (CR_of_Q_lt R _ _ H1)). 2: exact c1. exfalso. - clear H1 H q. - (* For an index high enough, xn should be both higher - and lower than r, which is absurd. *) - apply CRealLt_above in H0. - destruct H0 as [p pmaj]. simpl in pmaj. - destruct (CR_cv_above_rat R xn x r c0 c1). - assert (x0 <= Nat.max (Pos.to_nat p) (S x0))%nat. - { apply (le_trans _ (S x0)). apply le_S, le_refl. apply Nat.le_max_r. } - specialize (q (Nat.max (Pos.to_nat p) (S x0)) H). clear H. - specialize (pmaj (Pos.max p (Pos.of_nat (S x0))) (Pos.le_max_l _ _)). - rewrite Pos2Nat.inj_max, Nat2Pos.id in pmaj. 2: discriminate. - apply (Qlt_not_le _ _ q). apply Qlt_le_weak. - apply Qlt_minus_iff. apply (Qlt_trans _ (2#p)). reflexivity. exact pmaj. -Qed. - -Lemma CauchyMorph_increasing_Qr : forall (R : ConstructiveReals) (x : CReal) (q : Q), - CRealLt (inject_Q q) x -> CRlt R (CR_of_Q R q) (CauchyMorph R x). -Proof. - intros. - unfold CauchyMorph; simpl; - destruct x as [xn xcau], (CRltLinear R), p, (CR_complete R (fun n : nat => CR_of_Q R (xn n))). - destruct (CRealQ_dense _ _ H) as [r [H0 H1]]. - apply lt_inject_Q in H0. - destruct (s _ x _ (CR_of_Q_lt R _ _ H0)). exact c1. exfalso. - clear H0 H q. - (* For an index high enough, xn should be both higher - and lower than r, which is absurd. *) - apply CRealLt_above in H1. - destruct H1 as [p pmaj]. simpl in pmaj. - destruct (CR_cv_below_rat R xn x r c0 c1). - assert (x0 <= Nat.max (Pos.to_nat p) (S x0))%nat. - { apply (le_trans _ (S x0)). apply le_S, le_refl. apply Nat.le_max_r. } - specialize (q (Nat.max (Pos.to_nat p) (S x0)) H). clear H. - specialize (pmaj (Pos.max p (Pos.of_nat (S x0))) (Pos.le_max_l _ _)). - rewrite Pos2Nat.inj_max, Nat2Pos.id in pmaj. 2: discriminate. - apply (Qlt_not_le _ _ q). apply Qlt_le_weak. - apply Qlt_minus_iff. apply (Qlt_trans _ (2#p)). reflexivity. exact pmaj. -Qed. - -Lemma CauchyMorph_increasing : forall (R : ConstructiveReals) (x y : CReal), - CRealLt x y -> CRlt R (CauchyMorph R x) (CauchyMorph R y). -Proof. - intros. - destruct (CRealQ_dense _ _ H) as [q [H0 H1]]. - apply (CRlt_trans R _ (CR_of_Q R q)). - apply CauchyMorph_increasing_Ql. exact H0. - apply CauchyMorph_increasing_Qr. exact H1. -Qed. - -Definition CauchyMorphism (R : ConstructiveReals) : ConstructiveRealsMorphism CRealImplem R. -Proof. - apply (Build_ConstructiveRealsMorphism CRealImplem R (CauchyMorph R)). - exact (CauchyMorph_rat R). - exact (CauchyMorph_increasing R). -Defined. - -Lemma RightBound : forall (R : ConstructiveReals) (x : CRcarrier R) (p q r : Q), - CRlt R x (CR_of_Q R q) - -> CRlt R x (CR_of_Q R r) - -> CRlt R (CR_of_Q R q) (CRplus R x (CR_of_Q R p)) - -> CRlt R (CR_of_Q R r) (CRplus R x (CR_of_Q R p)) - -> Qlt (Qabs (q - r)) p. -Proof. - intros. apply Qabs_case. - - intros. apply (Qplus_lt_l _ _ r). ring_simplify. - apply (lt_CR_of_Q R), (CRlt_le_trans R _ _ _ H1). - apply (CRle_trans R _ (CRplus R (CR_of_Q R r) (CR_of_Q R p))). - intro abs. apply CRplus_lt_reg_r in abs. - exact (CRlt_asym R _ _ abs H0). - destruct (CR_of_Q_plus R r p). exact H4. - - intros. apply (Qplus_lt_l _ _ q). ring_simplify. - apply (lt_CR_of_Q R), (CRlt_le_trans R _ _ _ H2). - apply (CRle_trans R _ (CRplus R (CR_of_Q R q) (CR_of_Q R p))). - intro abs. apply CRplus_lt_reg_r in abs. - exact (CRlt_asym R _ _ abs H). - destruct (CR_of_Q_plus R q p). exact H4. -Qed. - -Definition CauchyMorph_inv (R : ConstructiveReals) - : CRcarrier R -> CReal. -Proof. - intro x. - exists (fun n:nat => let (q,_) := CR_Q_dense - R x _ (CRplus_pos_rat_lt R x (1 # Pos.of_nat (S n)) (eq_refl _)) - in q). - intros n p q H0 H1. - destruct (CR_Q_dense R x (CRplus R x (CR_of_Q R (1 # Pos.of_nat (S p)))) - (CRplus_pos_rat_lt R x (1 # Pos.of_nat (S p)) (eq_refl _))) - as [r [H2 H3]]. - destruct (CR_Q_dense R x (CRplus R x (CR_of_Q R (1 # Pos.of_nat (S q)))) - (CRplus_pos_rat_lt R x (1 # Pos.of_nat (S q)) (eq_refl _))) - as [s [H4 H5]]. - apply (RightBound R x (1#n) r s). exact H2. exact H4. - apply (CRlt_trans R _ _ _ H3), CRplus_lt_compat_l, CR_of_Q_lt. - unfold Qlt. do 2 rewrite Z.mul_1_l. unfold Qden. - apply Pos2Z.pos_lt_pos, Pos2Nat.inj_lt. rewrite Nat2Pos.id. - 2: discriminate. apply le_n_S. exact H0. - apply (CRlt_trans R _ _ _ H5), CRplus_lt_compat_l, CR_of_Q_lt. - unfold Qlt. do 2 rewrite Z.mul_1_l. unfold Qden. - apply Pos2Z.pos_lt_pos, Pos2Nat.inj_lt. rewrite Nat2Pos.id. - 2: discriminate. apply le_n_S. exact H1. -Defined. - -Lemma CauchyMorph_inv_rat : forall (R : ConstructiveReals) (q : Q), - CRealEq (CauchyMorph_inv R (CR_of_Q R q)) (inject_Q q). -Proof. - split. - - intros [n nmaj]. unfold CauchyMorph_inv, proj1_sig, inject_Q in nmaj. - destruct (CR_Q_dense R (CR_of_Q R q) - (CRplus R (CR_of_Q R q) (CR_of_Q R (1 # Pos.of_nat (S (Pos.to_nat n))))) - (CRplus_pos_rat_lt R (CR_of_Q R q) (1 # Pos.of_nat (S (Pos.to_nat n))) - eq_refl)) - as [r [H _]]. - apply lt_CR_of_Q, Qlt_minus_iff in H. - apply (Qlt_not_le _ _ H), (Qplus_le_l _ _ (q-r)). - ring_simplify. apply (Qle_trans _ (2#n)). discriminate. - apply Qlt_le_weak. ring_simplify in nmaj. rewrite Qplus_comm. exact nmaj. - - intros [n nmaj]. unfold CauchyMorph_inv, proj1_sig, inject_Q in nmaj. - destruct (CR_Q_dense R (CR_of_Q R q) - (CRplus R (CR_of_Q R q) (CR_of_Q R (1 # Pos.of_nat (S (Pos.to_nat n))))) - (CRplus_pos_rat_lt R (CR_of_Q R q) (1 # Pos.of_nat (S (Pos.to_nat n))) - eq_refl)) - as [r [_ H0]]. - destruct (CR_of_Q_plus R q (1 # Pos.of_nat (S (Pos.to_nat n)))) as [H1 _]. - apply (CRlt_le_trans R _ _ _ H0) in H1. clear H0. - apply lt_CR_of_Q, (Qplus_lt_l _ _ (-q)) in H1. - ring_simplify in H1. ring_simplify in nmaj. - apply (Qlt_trans _ _ _ nmaj) in H1. clear nmaj. - apply (Qlt_not_le _ _ H1). clear H1. - apply (Qle_trans _ (1#n)). - unfold Qle, Qnum, Qden. do 2 rewrite Z.mul_1_l. - apply Pos2Z.pos_le_pos. apply Pos2Nat.inj_le. - rewrite Nat2Pos.id. 2: discriminate. apply le_S, le_refl. - unfold Qle, Qnum, Qden. apply Z.mul_le_mono_nonneg_r. - 2: discriminate. apply Pos2Z.pos_is_nonneg. -Qed. - -(* The easier side, because CauchyMorph_inv takes a limit from above. *) -Lemma CauchyMorph_inv_increasing_Qr - : forall (R : ConstructiveReals) (x : CRcarrier R) (q : Q), - CRlt R (CR_of_Q R q) x -> CRealLt (inject_Q q) (CauchyMorph_inv R x). -Proof. - intros. - destruct (CR_Q_dense R _ _ H) as [r [H2 H3]]. - apply lt_CR_of_Q in H2. - destruct (Qarchimedean (/(r-q))) as [p pmaj]. - exists (2*p)%positive. unfold CauchyMorph_inv, inject_Q, proj1_sig. - destruct (CR_Q_dense - R x (CRplus R x (CR_of_Q R (1 # Pos.of_nat (S (Pos.to_nat (2*p)))))) - (CRplus_pos_rat_lt R x (1 # Pos.of_nat (S (Pos.to_nat (2*p)))) eq_refl)) - as [t [H4 H5]]. - setoid_replace (2#2*p) with (1#p). 2: reflexivity. - apply (Qlt_trans _ (r-q)). - apply (Qmult_lt_l _ _ (r-q)) in pmaj. - rewrite Qmult_inv_r in pmaj. - apply Qlt_shift_inv_r in pmaj. 2: reflexivity. exact pmaj. - intro abs. apply Qlt_minus_iff in H2. - rewrite abs in H2. inversion H2. - apply Qlt_minus_iff in H2. exact H2. - apply Qplus_lt_l, (lt_CR_of_Q R), (CRlt_trans R _ x _ H3 H4). -Qed. - -Lemma CauchyMorph_inv_increasing : forall (R : ConstructiveReals) (x y : CRcarrier R), - CRlt R x y -> CRealLt (CauchyMorph_inv R x) (CauchyMorph_inv R y). -Proof. - intros. - destruct (CR_Q_dense R _ _ H) as [q [H0 H1]]. - apply (CReal_lt_trans _ (inject_Q q)). - - clear H1 H y. - destruct (CR_Q_dense R _ _ H0) as [r [H2 H3]]. - apply lt_CR_of_Q in H3. - destruct (Qarchimedean (/(q-r))) as [p pmaj]. - exists (4*p)%positive. unfold CauchyMorph_inv, inject_Q, proj1_sig. - destruct (CR_Q_dense - R x (CRplus R x (CR_of_Q R (1 # Pos.of_nat (S (Pos.to_nat (4*p)))))) - (CRplus_pos_rat_lt R x (1 # Pos.of_nat (S (Pos.to_nat (4*p)))) eq_refl)) - as [t [H4 H5]]. - setoid_replace (2#4*p) with (1#2*p). 2: reflexivity. - assert (1 # 2 * p < (q - r) / 2) as H. - { apply Qlt_shift_div_l. reflexivity. - setoid_replace ((1#2*p)*2) with (1#p). - apply (Qmult_lt_l _ _ (q-r)) in pmaj. - rewrite Qmult_inv_r in pmaj. - apply Qlt_shift_inv_r in pmaj. 2: reflexivity. exact pmaj. - intro abs. apply Qlt_minus_iff in H3. - rewrite abs in H3. inversion H3. - apply Qlt_minus_iff in H3. exact H3. - rewrite Qmult_comm. reflexivity. } - apply (Qlt_trans _ ((q-r)/2)). exact H. - apply (Qplus_lt_l _ _ (t + (r-q)/2)). field_simplify. - setoid_replace (2*t/2) with t. 2: field. - apply (lt_CR_of_Q R). apply (CRlt_trans R _ _ _ H5). - apply (CRlt_trans - R _ (CRplus R (CR_of_Q R r) (CR_of_Q R (1 # Pos.of_nat (S (Pos.to_nat (4 * p))))))). - apply CRplus_lt_compat_r. exact H2. - apply (CRle_lt_trans - R _ (CR_of_Q R (r + (1 # Pos.of_nat (S (Pos.to_nat (4 * p))))))). - apply CR_of_Q_plus. apply CR_of_Q_lt. - apply (Qlt_le_trans _ (r + (q-r)/2)). - 2: field_simplify; apply Qle_refl. - apply Qplus_lt_r. - apply (Qlt_trans _ (1#2*p)). 2: exact H. - unfold Qlt. do 2 rewrite Z.mul_1_l. unfold Qden. - apply Pos2Z.pos_lt_pos. - rewrite Nat2Pos.inj_succ, Pos2Nat.id. - apply (Pos.lt_trans _ (4*p)). apply Pos2Nat.inj_lt. - do 2 rewrite Pos2Nat.inj_mul. - apply Nat.mul_lt_mono_pos_r. apply Pos2Nat.is_pos. - unfold Pos.to_nat. simpl. auto. - apply Pos.lt_succ_diag_r. - intro abs. pose proof (Pos2Nat.is_pos (4*p)). - rewrite abs in H1. inversion H1. - - apply CauchyMorph_inv_increasing_Qr. exact H1. -Qed. - -Definition CauchyMorphismInv (R : ConstructiveReals) - : ConstructiveRealsMorphism R CRealImplem. -Proof. - apply (Build_ConstructiveRealsMorphism R CRealImplem (CauchyMorph_inv R)). - - apply CauchyMorph_inv_rat. - - apply CauchyMorph_inv_increasing. -Defined. - -Lemma CauchyMorph_surject : forall (R : ConstructiveReals) (x : CRcarrier R), - orderEq _ (CRlt R) (CauchyMorph R (CauchyMorph_inv R x)) x. -Proof. - intros. - apply (Endomorph_id - R (CRmorph_compose _ _ _ (CauchyMorphismInv R) (CauchyMorphism R)) x). -Qed. - -Lemma CauchyMorph_inject : forall (R : ConstructiveReals) (x : CReal), - CRealEq (CauchyMorph_inv R (CauchyMorph R x)) x. -Proof. - intros. - apply (Endomorph_id CRealImplem (CRmorph_compose _ _ _ (CauchyMorphism R) (CauchyMorphismInv R)) x). -Qed. - -(* We call this morphism slow to remind that it should only be used - for proofs, not for computations. *) -Definition SlowConstructiveRealsMorphism (R1 R2 : ConstructiveReals) - : ConstructiveRealsMorphism R1 R2 - := CRmorph_compose R1 CRealImplem R2 - (CauchyMorphismInv R1) (CauchyMorphism R2). diff --git a/theories/Reals/Machin.v b/theories/Reals/Machin.v index d345158d1a..7c3b9097e5 100644 --- a/theories/Reals/Machin.v +++ b/theories/Reals/Machin.v @@ -39,11 +39,11 @@ assert (cos (atan v) <> 0). destruct (atan_bound v); apply Rgt_not_eq, cos_gt_0; auto. rewrite <- Ropp_div; assumption. assert (t : forall a b c, a - b = c -> a = b + c) by (intros; subst; field). -apply t, tan_is_inj; clear t; try assumption. +apply t, tan_inj; clear t; try assumption. rewrite tan_minus; auto. - rewrite !atan_right_inv; reflexivity. + rewrite !tan_atan; reflexivity. apply Rgt_not_eq, cos_gt_0; rewrite <- ?Ropp_div; tauto. -rewrite !atan_right_inv; assumption. +rewrite !tan_atan; assumption. Qed. Lemma tech : forall x y , -1 <= x <= 1 -> -1 < y < 1 -> diff --git a/theories/Reals/RIneq.v b/theories/Reals/RIneq.v index c5fcb49b82..33e40a115b 100644 --- a/theories/Reals/RIneq.v +++ b/theories/Reals/RIneq.v @@ -746,6 +746,9 @@ Proof. Qed. Hint Resolve Rminus_diag_eq: real. +Lemma Rminus_eq_0 x : x - x = 0. +Proof. ring. Qed. + (**********) Lemma Rminus_diag_uniq : forall r1 r2, r1 - r2 = 0 -> r1 = r2. Proof. @@ -794,6 +797,10 @@ Proof. intros; ring. Qed. +Lemma Rmult_minus_distr_r: + forall r1 r2 r3, (r2 - r3) * r1 = r2 * r1 - r3 * r1. +Proof. intros; ring. Qed. + (*********************************************************) (** ** Inverse *) (*********************************************************) @@ -823,7 +830,7 @@ Hint Resolve Rinv_involutive: real. Lemma Rinv_mult_distr : forall r1 r2, r1 <> 0 -> r2 <> 0 -> / (r1 * r2) = / r1 * / r2. Proof. - intros; field; auto. + intros; field; auto. Qed. (*********) @@ -2017,6 +2024,12 @@ Lemma Ropp_div : forall x y, -x/y = - (x / y). intros x y; unfold Rdiv; ring. Qed. +Lemma Ropp_div_den : forall x y : R, y<>0 -> x / - y = - (x / y). +Proof. + intros. + field; assumption. +Qed. + Lemma double : forall r1, 2 * r1 = r1 + r1. Proof. intro; ring. @@ -2130,6 +2143,15 @@ Record negreal : Type := mknegreal {neg :> R; cond_neg : neg < 0}. Record nonzeroreal : Type := mknonzeroreal {nonzero :> R; cond_nonzero : nonzero <> 0}. +(** ** A few common instances *) + +Lemma pos_half_prf : 0 < /2. +Proof. + apply Rinv_0_lt_compat, Rlt_0_2. +Qed. + +Definition posreal_one := mkposreal (1) (Rlt_0_1). +Definition posreal_half := mkposreal (/2) pos_half_prf. (** Compatibility *) diff --git a/theories/Reals/R_sqr.v b/theories/Reals/R_sqr.v index 12f5ece2cf..f17961aa7a 100644 --- a/theories/Reals/R_sqr.v +++ b/theories/Reals/R_sqr.v @@ -72,7 +72,7 @@ Proof. rewrite Rinv_mult_distr. repeat rewrite Rmult_assoc. apply Rmult_eq_compat_l. - rewrite Rmult_comm. + rewrite Rmult_comm. repeat rewrite Rmult_assoc. apply Rmult_eq_compat_l. reflexivity. @@ -181,6 +181,38 @@ Proof. apply Rsqr_incr_1; assumption. Qed. +Lemma neg_pos_Rsqr_lt : forall x y : R, - y < x -> x < y -> Rsqr x < Rsqr y. +Proof. + intros x y Hneg Hpos. + destruct (Rcase_abs x) as [Hlt|HLe]. + - rewrite (Rsqr_neg x); apply Rsqr_incrst_1. + + rewrite <- (Ropp_involutive y); apply Ropp_lt_contravar; exact Hneg. + + rewrite <- (Ropp_0). apply Ropp_le_contravar, Rlt_le; exact Hlt. + + apply (Rlt_trans _ _ _ Hneg) in Hlt. + rewrite <- (Ropp_0) in Hlt; apply Ropp_lt_cancel in Hlt; apply Rlt_le; exact Hlt. + - apply Rsqr_incrst_1. + + exact Hpos. + + apply Rge_le; exact HLe. + + apply Rge_le in HLe. + apply (Rle_lt_trans _ _ _ HLe), Rlt_le in Hpos; exact Hpos. +Qed. + +Lemma Rsqr_bounds_le : forall a b:R, -a <= b <= a -> 0 <= Rsqr b <= Rsqr a. +Proof. + intros a b [H1 H2]. + split. + - apply Rle_0_sqr. + - apply neg_pos_Rsqr_le; assumption. +Qed. + +Lemma Rsqr_bounds_lt : forall a b:R, -a < b < a -> 0 <= Rsqr b < Rsqr a. +Proof. + intros a b [H1 H2]. + split. + - apply Rle_0_sqr. + - apply neg_pos_Rsqr_lt; assumption. +Qed. + Lemma Rsqr_abs : forall x:R, Rsqr x = Rsqr (Rabs x). Proof. intro; unfold Rabs; case (Rcase_abs x); intro; diff --git a/theories/Reals/R_sqrt.v b/theories/Reals/R_sqrt.v index b5d43b3c4c..7961a178b1 100644 --- a/theories/Reals/R_sqrt.v +++ b/theories/Reals/R_sqrt.v @@ -100,6 +100,9 @@ Lemma sqrt_pow2 : forall x, 0 <= x -> sqrt (x ^ 2) = x. intros; simpl; rewrite Rmult_1_r, sqrt_square; auto. Qed. +Lemma pow2_sqrt x : 0 <= x -> sqrt x ^ 2 = x. +Proof. now intros x0; simpl; rewrite -> Rmult_1_r, sqrt_sqrt. Qed. + Lemma sqrt_Rsqr_abs : forall x:R, sqrt (Rsqr x) = Rabs x. Proof. intro x; rewrite Rsqr_abs; apply sqrt_Rsqr; apply Rabs_pos. @@ -290,6 +293,14 @@ Proof. now apply sqrt_le_1_alt. Qed. +Lemma sqrt_neg_0 x : x <= 0 -> sqrt x = 0. +Proof. + intros Hx. + apply Rle_le_eq; split. + - rewrite <- sqrt_0; apply sqrt_le_1_alt, Hx. + - apply sqrt_pos. +Qed. + Lemma sqrt_inj : forall x y:R, 0 <= x -> 0 <= y -> sqrt x = sqrt y -> x = y. Proof. intros; cut (Rsqr (sqrt x) = Rsqr (sqrt y)). @@ -327,6 +338,20 @@ Proof. apply (Rmult_lt_compat_l (sqrt x) (sqrt x) 1 (sqrt_lt_R0 x H1) H3). Qed. +Lemma inv_sqrt x : 0 < x -> / sqrt x = sqrt (/ x). +Proof. +intros x0. +assert (sqrt x <> 0). + apply Rgt_not_eq. + now apply sqrt_lt_R0. +apply Rmult_eq_reg_r with (sqrt x); auto. +rewrite Rinv_l; auto. +rewrite <- sqrt_mult_alt. + now rewrite -> Rinv_l, sqrt_1; auto with real. +apply Rlt_le. +now apply Rinv_0_lt_compat. +Qed. + Lemma sqrt_cauchy : forall a b c d:R, a * c + b * d <= sqrt (Rsqr a + Rsqr b) * sqrt (Rsqr c + Rsqr d). diff --git a/theories/Reals/Ranalysis1.v b/theories/Reals/Ranalysis1.v index 8ba4057e03..6594648489 100644 --- a/theories/Reals/Ranalysis1.v +++ b/theories/Reals/Ranalysis1.v @@ -27,6 +27,7 @@ Definition div_fct f1 f2 (x:R) : R := f1 x / f2 x. Definition div_real_fct (a:R) f (x:R) : R := a / f x. Definition comp f1 f2 (x:R) : R := f1 (f2 x). Definition inv_fct f (x:R) : R := / f x. +Definition mirr_fct f (x:R) : R := f (- x). Declare Scope Rfun_scope. Delimit Scope Rfun_scope with F. @@ -40,6 +41,7 @@ Arguments opp_fct f%F x%R. Arguments mult_real_fct a%R f%F x%R. Arguments div_real_fct a%R f%F x%R. Arguments comp (f1 f2)%F x%R. +Arguments mirr_fct f%F x%R. Infix "+" := plus_fct : Rfun_scope. Notation "- x" := (opp_fct x) : Rfun_scope. @@ -92,7 +94,7 @@ exists (Rmin a a'); split. intros y cy; rewrite <- !q. apply Pa'. split;[| apply Rlt_le_trans with (Rmin a a');[ | apply Rmin_r]];tauto. - rewrite R_dist_eq; assumption. + rewrite R_dist_eq; assumption. apply Rlt_le_trans with (Rmin a a');[ | apply Rmin_l]; tauto. Qed. @@ -499,7 +501,7 @@ Qed. (* Extensionally equal functions have the same derivative. *) -Lemma derivable_pt_lim_ext : forall f g x l, (forall z, f z = g z) -> +Lemma derivable_pt_lim_ext : forall f g x l, (forall z, f z = g z) -> derivable_pt_lim f x l -> derivable_pt_lim g x l. intros f g x l fg df e ep; destruct (df e ep) as [d pd]; exists d; intros h; rewrite <- !fg; apply pd. @@ -507,7 +509,7 @@ Qed. (* extensionally equal functions have the same derivative, locally. *) -Lemma derivable_pt_lim_locally_ext : forall f g x a b l, +Lemma derivable_pt_lim_locally_ext : forall f g x a b l, a < x < b -> (forall z, a < z < b -> f z = g z) -> derivable_pt_lim f x l -> derivable_pt_lim g x l. @@ -577,6 +579,124 @@ Qed. (** * Main rules *) (****************************************************************) +(** ** Rules for derivable_pt_lim (value of the derivative at a point) *) + +Lemma derivable_pt_lim_id : forall x:R, derivable_pt_lim id x 1. +Proof. + intro; unfold derivable_pt_lim. + intros eps Heps; exists (mkposreal eps Heps); intros h H1 H2; + unfold id; replace ((x + h - x) / h - 1) with 0. + rewrite Rabs_R0; apply Rle_lt_trans with (Rabs h). + apply Rabs_pos. + assumption. + unfold Rminus; rewrite Rplus_assoc; rewrite (Rplus_comm x); + rewrite Rplus_assoc. + rewrite Rplus_opp_l; rewrite Rplus_0_r; unfold Rdiv; + rewrite <- Rinv_r_sym. + symmetry ; apply Rplus_opp_r. + assumption. +Qed. + +Lemma derivable_pt_lim_comp : + forall f1 f2 (x l1 l2:R), + derivable_pt_lim f1 x l1 -> + derivable_pt_lim f2 (f1 x) l2 -> derivable_pt_lim (f2 o f1) x (l2 * l1). +Proof. + intros; assert (H1 := derivable_pt_lim_D_in f1 (fun y:R => l1) x). + elim H1; intros. + assert (H4 := H3 H). + assert (H5 := derivable_pt_lim_D_in f2 (fun y:R => l2) (f1 x)). + elim H5; intros. + assert (H8 := H7 H0). + clear H1 H2 H3 H5 H6 H7. + assert (H1 := derivable_pt_lim_D_in (f2 o f1)%F (fun y:R => l2 * l1) x). + elim H1; intros. + clear H1 H3; apply H2. + unfold comp; + cut + (D_in (fun x0:R => f2 (f1 x0)) (fun y:R => l2 * l1) + (Dgf no_cond no_cond f1) x -> + D_in (fun x0:R => f2 (f1 x0)) (fun y:R => l2 * l1) no_cond x). + intro; apply H1. + rewrite Rmult_comm; + apply (Dcomp no_cond no_cond (fun y:R => l1) (fun y:R => l2) f1 f2 x); + assumption. + unfold Dgf, D_in, no_cond; unfold limit1_in; + unfold limit_in; unfold dist; simpl; + unfold R_dist; intros. + elim (H1 eps H3); intros. + exists x0; intros; split. + elim H5; intros; assumption. + intros; elim H5; intros; apply H9; split. + unfold D_x; split. + split; trivial. + elim H6; intros; unfold D_x in H10; elim H10; intros; assumption. + elim H6; intros; assumption. +Qed. + +Lemma derivable_pt_lim_opp : + forall f (x l:R), derivable_pt_lim f x l -> derivable_pt_lim (- f) x (- l). +Proof. + intros f x l H. + apply uniqueness_step3. + unfold opp_fct, limit1_in, limit_in, dist; simpl; unfold R_dist. + apply uniqueness_step2 in H. + unfold limit1_in, limit_in, dist in H; simpl in H; unfold R_dist in H. + intros eps Heps; specialize (H eps Heps). + destruct H as [alp [Halp H]]; exists alp. + split; [assumption|]. + intros x0 Hx0; specialize(H x0 Hx0). + rewrite <- Rabs_Ropp in H. + match goal with H:Rabs(?a)<eps |- Rabs(?b)<eps => replace b with a by (field; tauto) end. + assumption. +Qed. + +Lemma derivable_pt_lim_opp_fwd : + forall f (x l:R), derivable_pt_lim f x (- l) -> derivable_pt_lim (- f) x l. +Proof. + intros f x l H. + apply uniqueness_step3. + unfold opp_fct, limit1_in, limit_in, dist; simpl; unfold R_dist. + apply uniqueness_step2 in H. + unfold limit1_in, limit_in, dist in H; simpl in H; unfold R_dist in H. + intros eps Heps; specialize (H eps Heps). + destruct H as [alp [Halp H]]; exists alp. + split; [assumption|]. + intros x0 Hx0; specialize(H x0 Hx0). + rewrite <- Rabs_Ropp in H. + match goal with H:Rabs(?a)<eps |- Rabs(?b)<eps => replace b with a by (field; tauto) end. + assumption. +Qed. + +Lemma derivable_pt_lim_opp_rev : + forall f (x l:R), derivable_pt_lim (- f) x (- l) -> derivable_pt_lim f x l. +Proof. + intros f x l H. + apply derivable_pt_lim_ext with (f := fun x => - - (f x)). + - intros; rewrite Ropp_involutive; reflexivity. + - apply derivable_pt_lim_opp_fwd; exact H. +Qed. + +Lemma derivable_pt_lim_mirr_fwd : + forall f (x l:R), derivable_pt_lim f (- x) (- l) -> derivable_pt_lim (mirr_fct f) x l. +Proof. + intros f x l H. + change (mirr_fct f) with (comp f (opp_fct id)). + replace l with ((-l) * -1) by ring. + apply derivable_pt_lim_comp; [| exact H]. + apply derivable_pt_lim_opp. + apply derivable_pt_lim_id. +Qed. + +Lemma derivable_pt_lim_mirr_rev : + forall f (x l:R), derivable_pt_lim (mirr_fct f) (- x) (- l) -> derivable_pt_lim f x l. +Proof. + intros f x l H. + apply derivable_pt_lim_ext with (f := fun x => (mirr_fct f (- x))). + - intros; unfold mirr_fct; rewrite Ropp_involutive; reflexivity. + - apply derivable_pt_lim_mirr_fwd; exact H. +Qed. + Lemma derivable_pt_lim_plus : forall f1 f2 (x l1 l2:R), derivable_pt_lim f1 x l1 -> @@ -605,28 +725,6 @@ Lemma derivable_pt_lim_plus : intro; unfold Rdiv; ring. Qed. -Lemma derivable_pt_lim_opp : - forall f (x l:R), derivable_pt_lim f x l -> derivable_pt_lim (- f) x (- l). -Proof. - intros. - apply uniqueness_step3. - assert (H1 := uniqueness_step2 _ _ _ H). - unfold opp_fct. - cut (forall h:R, (- f (x + h) - - f x) / h = - ((f (x + h) - f x) / h)). - intro. - generalize - (limit_Ropp (fun h:R => (f (x + h) - f x) / h) (fun h:R => h <> 0) l 0 H1). - unfold limit1_in; unfold limit_in; unfold dist; - simpl; unfold R_dist; intros. - elim (H2 eps H3); intros. - exists x0. - elim H4; intros. - split. - assumption. - intros; rewrite H0; apply H6; assumption. - intro; unfold Rdiv; ring. -Qed. - Lemma derivable_pt_lim_minus : forall f1 f2 (x l1 l2:R), derivable_pt_lim f1 x l1 -> @@ -718,22 +816,6 @@ intros f x l a df; unfold Rdiv; rewrite Rmult_comm; apply derivable_pt_lim_scal; assumption. Qed. -Lemma derivable_pt_lim_id : forall x:R, derivable_pt_lim id x 1. -Proof. - intro; unfold derivable_pt_lim. - intros eps Heps; exists (mkposreal eps Heps); intros h H1 H2; - unfold id; replace ((x + h - x) / h - 1) with 0. - rewrite Rabs_R0; apply Rle_lt_trans with (Rabs h). - apply Rabs_pos. - assumption. - unfold Rminus; rewrite Rplus_assoc; rewrite (Rplus_comm x); - rewrite Rplus_assoc. - rewrite Rplus_opp_l; rewrite Rplus_0_r; unfold Rdiv; - rewrite <- Rinv_r_sym. - symmetry ; apply Rplus_opp_r. - assumption. -Qed. - Lemma derivable_pt_lim_Rsqr : forall x:R, derivable_pt_lim Rsqr x (2 * x). Proof. intro; unfold derivable_pt_lim. @@ -748,63 +830,93 @@ Proof. ring. Qed. -Lemma derivable_pt_lim_comp : - forall f1 f2 (x l1 l2:R), - derivable_pt_lim f1 x l1 -> - derivable_pt_lim f2 (f1 x) l2 -> derivable_pt_lim (f2 o f1) x (l2 * l1). +(** ** Rules for derivable_pt (derivability at a point) *) + +Lemma derivable_pt_id : forall x:R, derivable_pt id x. Proof. - intros; assert (H1 := derivable_pt_lim_D_in f1 (fun y:R => l1) x). - elim H1; intros. - assert (H4 := H3 H). - assert (H5 := derivable_pt_lim_D_in f2 (fun y:R => l2) (f1 x)). - elim H5; intros. - assert (H8 := H7 H0). - clear H1 H2 H3 H5 H6 H7. - assert (H1 := derivable_pt_lim_D_in (f2 o f1)%F (fun y:R => l2 * l1) x). - elim H1; intros. - clear H1 H3; apply H2. - unfold comp; - cut - (D_in (fun x0:R => f2 (f1 x0)) (fun y:R => l2 * l1) - (Dgf no_cond no_cond f1) x -> - D_in (fun x0:R => f2 (f1 x0)) (fun y:R => l2 * l1) no_cond x). - intro; apply H1. - rewrite Rmult_comm; - apply (Dcomp no_cond no_cond (fun y:R => l1) (fun y:R => l2) f1 f2 x); - assumption. - unfold Dgf, D_in, no_cond; unfold limit1_in; - unfold limit_in; unfold dist; simpl; - unfold R_dist; intros. - elim (H1 eps H3); intros. - exists x0; intros; split. - elim H5; intros; assumption. - intros; elim H5; intros; apply H9; split. - unfold D_x; split. - split; trivial. - elim H6; intros; unfold D_x in H10; elim H10; intros; assumption. - elim H6; intros; assumption. + unfold derivable_pt; intro. + exists 1. + apply derivable_pt_lim_id. Qed. -Lemma derivable_pt_plus : +Lemma derivable_pt_comp : forall f1 f2 (x:R), - derivable_pt f1 x -> derivable_pt f2 x -> derivable_pt (f1 + f2) x. + derivable_pt f1 x -> derivable_pt f2 (f1 x) -> derivable_pt (f2 o f1) x. Proof. unfold derivable_pt; intros f1 f2 x X X0. elim X; intros. elim X0; intros. - exists (x0 + x1). - apply derivable_pt_lim_plus; assumption. + exists (x1 * x0). + apply derivable_pt_lim_comp; assumption. +Qed. + +Lemma derivable_pt_xeq: + forall (f : R -> R) (x1 x2 : R), x1=x2 -> derivable_pt f x1 -> derivable_pt f x2. +Proof. + intros f x1 x2 Heq H. + subst; assumption. Qed. Lemma derivable_pt_opp : - forall f (x:R), derivable_pt f x -> derivable_pt (- f) x. + forall (f : R -> R) (x:R), derivable_pt f x -> derivable_pt (- f) x. Proof. - unfold derivable_pt; intros f x X. - elim X; intros. - exists (- x0). + intros f x H. + unfold derivable_pt in H. + destruct H as [l H]; exists (-l). apply derivable_pt_lim_opp; assumption. Qed. +Lemma derivable_pt_opp_rev: + forall (f : R -> R) (x : R), derivable_pt (- f) x -> derivable_pt f x. +Proof. + intros f x H. + unfold derivable_pt in H. + destruct H as [l H]; exists (-l). + apply derivable_pt_lim_opp_rev. + rewrite Ropp_involutive; assumption. +Qed. + +Lemma derivable_pt_mirr: + forall (f : R -> R) (x : R), derivable_pt f (-x) -> derivable_pt (mirr_fct f) x. +Proof. + intros f x H. + unfold derivable_pt in H. + destruct H as [l H]; exists (-l). + apply derivable_pt_lim_mirr_fwd. + rewrite Ropp_involutive; assumption. +Qed. + +Lemma derivable_pt_mirr_rev: + forall (f : R -> R) (x : R), derivable_pt (mirr_fct f) (- x) -> derivable_pt f x. +Proof. + intros f x H. + unfold derivable_pt in H. + destruct H as [l H]; exists (-l). + apply derivable_pt_lim_mirr_rev. + rewrite Ropp_involutive; assumption. +Qed. + +Lemma derivable_pt_mirr_prem: + forall (f : R -> R) (x : R), derivable_pt (mirr_fct f) x -> derivable_pt f (-x). +Proof. + intros f x H. + unfold derivable_pt in H. + destruct H as [l H]; exists (-l). + apply derivable_pt_lim_mirr_rev. + repeat rewrite Ropp_involutive; assumption. +Qed. + +Lemma derivable_pt_plus : + forall f1 f2 (x:R), + derivable_pt f1 x -> derivable_pt f2 x -> derivable_pt (f1 + f2) x. +Proof. + unfold derivable_pt; intros f1 f2 x X X0. + elim X; intros. + elim X0; intros. + exists (x0 + x1). + apply derivable_pt_lim_plus; assumption. +Qed. + Lemma derivable_pt_minus : forall f1 f2 (x:R), derivable_pt f1 x -> derivable_pt f2 x -> derivable_pt (f1 - f2) x. @@ -843,35 +955,24 @@ Proof. apply derivable_pt_lim_scal; assumption. Qed. -Lemma derivable_pt_id : forall x:R, derivable_pt id x. -Proof. - unfold derivable_pt; intro. - exists 1. - apply derivable_pt_lim_id. -Qed. - Lemma derivable_pt_Rsqr : forall x:R, derivable_pt Rsqr x. Proof. unfold derivable_pt; intro; exists (2 * x). apply derivable_pt_lim_Rsqr. Qed. -Lemma derivable_pt_comp : - forall f1 f2 (x:R), - derivable_pt f1 x -> derivable_pt f2 (f1 x) -> derivable_pt (f2 o f1) x. +(** ** Rules for derivable (derivability on whole domain) *) + +Lemma derivable_id : derivable id. Proof. - unfold derivable_pt; intros f1 f2 x X X0. - elim X; intros. - elim X0; intros. - exists (x1 * x0). - apply derivable_pt_lim_comp; assumption. + unfold derivable; intro; apply derivable_pt_id. Qed. -Lemma derivable_plus : - forall f1 f2, derivable f1 -> derivable f2 -> derivable (f1 + f2). +Lemma derivable_comp : + forall f1 f2, derivable f1 -> derivable f2 -> derivable (f2 o f1). Proof. unfold derivable; intros f1 f2 X X0 x. - apply (derivable_pt_plus _ _ x (X _) (X0 _)). + apply (derivable_pt_comp _ _ x (X _) (X0 _)). Qed. Lemma derivable_opp : forall f, derivable f -> derivable (- f). @@ -880,6 +981,19 @@ Proof. apply (derivable_pt_opp _ x (X _)). Qed. +Lemma derivable_mirr : forall f, derivable f -> derivable (mirr_fct f). +Proof. + unfold derivable; intros f X x. + apply (derivable_pt_mirr _ x (X _)). +Qed. + +Lemma derivable_plus : + forall f1 f2, derivable f1 -> derivable f2 -> derivable (f1 + f2). +Proof. + unfold derivable; intros f1 f2 X X0 x. + apply (derivable_pt_plus _ _ x (X _) (X0 _)). +Qed. + Lemma derivable_minus : forall f1 f2, derivable f1 -> derivable f2 -> derivable (f1 - f2). Proof. @@ -907,33 +1021,30 @@ Proof. apply (derivable_pt_scal _ a x (X _)). Qed. -Lemma derivable_id : derivable id. -Proof. - unfold derivable; intro; apply derivable_pt_id. -Qed. - Lemma derivable_Rsqr : derivable Rsqr. Proof. unfold derivable; intro; apply derivable_pt_Rsqr. Qed. -Lemma derivable_comp : - forall f1 f2, derivable f1 -> derivable f2 -> derivable (f2 o f1). +(** ** Rules for derive_pt (derivative function on whole domain) *) + +Lemma derive_pt_id : forall x:R, derive_pt id x (derivable_pt_id _) = 1. Proof. - unfold derivable; intros f1 f2 X X0 x. - apply (derivable_pt_comp _ _ x (X _) (X0 _)). + intros. + apply derive_pt_eq_0. + apply derivable_pt_lim_id. Qed. -Lemma derive_pt_plus : - forall f1 f2 (x:R) (pr1:derivable_pt f1 x) (pr2:derivable_pt f2 x), - derive_pt (f1 + f2) x (derivable_pt_plus _ _ _ pr1 pr2) = - derive_pt f1 x pr1 + derive_pt f2 x pr2. +Lemma derive_pt_comp : + forall f1 f2 (x:R) (pr1:derivable_pt f1 x) (pr2:derivable_pt f2 (f1 x)), + derive_pt (f2 o f1) x (derivable_pt_comp _ _ _ pr1 pr2) = + derive_pt f2 (f1 x) pr2 * derive_pt f1 x pr1. Proof. intros. assert (H := derivable_derive f1 x pr1). - assert (H0 := derivable_derive f2 x pr2). + assert (H0 := derivable_derive f2 (f1 x) pr2). assert - (H1 := derivable_derive (f1 + f2)%F x (derivable_pt_plus _ _ _ pr1 pr2)). + (H1 := derivable_derive (f2 o f1)%F x (derivable_pt_comp _ _ _ pr1 pr2)). elim H; clear H; intros l1 H. elim H0; clear H0; intros l2 H0. elim H1; clear H1; intros l H1. @@ -942,7 +1053,7 @@ Proof. unfold derive_pt in H; rewrite H in H3. assert (H4 := proj2_sig pr2). unfold derive_pt in H0; rewrite H0 in H4. - apply derivable_pt_lim_plus; assumption. + apply derivable_pt_lim_comp; assumption. Qed. Lemma derive_pt_opp : @@ -950,14 +1061,68 @@ Lemma derive_pt_opp : derive_pt (- f) x (derivable_pt_opp _ _ pr1) = - derive_pt f x pr1. Proof. intros. - assert (H := derivable_derive f x pr1). - assert (H0 := derivable_derive (- f)%F x (derivable_pt_opp _ _ pr1)). + apply derive_pt_eq_0. + apply derivable_pt_lim_opp_fwd. + rewrite Ropp_involutive. + apply (derive_pt_eq_1 _ _ _ pr1). + reflexivity. +Qed. + +Lemma derive_pt_opp_rev : + forall f (x:R) (pr1:derivable_pt (- f) x), + derive_pt (- f) x pr1 = - derive_pt f x (derivable_pt_opp_rev _ _ pr1). +Proof. + intros. + apply derive_pt_eq_0. + apply derivable_pt_lim_opp_fwd. + rewrite Ropp_involutive. + apply (derive_pt_eq_1 _ _ _ (derivable_pt_opp_rev _ _ pr1)). + reflexivity. +Qed. + +Lemma derive_pt_mirr : + forall f (x:R) (pr1:derivable_pt f (-x)), + derive_pt (mirr_fct f) x (derivable_pt_mirr _ _ pr1) = - derive_pt f (-x) pr1. +Proof. + intros. + apply derive_pt_eq_0. + apply derivable_pt_lim_mirr_fwd. + rewrite Ropp_involutive. + apply (derive_pt_eq_1 _ _ _ pr1). + reflexivity. +Qed. + +Lemma derive_pt_mirr_rev : + forall f (x:R) (pr1:derivable_pt (mirr_fct f) x), + derive_pt (mirr_fct f) x pr1 = - derive_pt f (-x) (derivable_pt_mirr_prem f x pr1). +Proof. + intros. + apply derive_pt_eq_0. + apply derivable_pt_lim_mirr_fwd. + rewrite Ropp_involutive. + apply (derive_pt_eq_1 _ _ _ (derivable_pt_mirr_prem f x pr1)). + reflexivity. +Qed. + +Lemma derive_pt_plus : + forall f1 f2 (x:R) (pr1:derivable_pt f1 x) (pr2:derivable_pt f2 x), + derive_pt (f1 + f2) x (derivable_pt_plus _ _ _ pr1 pr2) = + derive_pt f1 x pr1 + derive_pt f2 x pr2. +Proof. + intros. + assert (H := derivable_derive f1 x pr1). + assert (H0 := derivable_derive f2 x pr2). + assert + (H1 := derivable_derive (f1 + f2)%F x (derivable_pt_plus _ _ _ pr1 pr2)). elim H; clear H; intros l1 H. elim H0; clear H0; intros l2 H0. - rewrite H; apply derive_pt_eq_0. + elim H1; clear H1; intros l H1. + rewrite H; rewrite H0; apply derive_pt_eq_0. assert (H3 := proj2_sig pr1). unfold derive_pt in H; rewrite H in H3. - apply derivable_pt_lim_opp; assumption. + assert (H4 := proj2_sig pr2). + unfold derive_pt in H0; rewrite H0 in H4. + apply derivable_pt_lim_plus; assumption. Qed. Lemma derive_pt_minus : @@ -1027,13 +1192,6 @@ Proof. apply derivable_pt_lim_scal; assumption. Qed. -Lemma derive_pt_id : forall x:R, derive_pt id x (derivable_pt_id _) = 1. -Proof. - intros. - apply derive_pt_eq_0. - apply derivable_pt_lim_id. -Qed. - Lemma derive_pt_Rsqr : forall x:R, derive_pt Rsqr x (derivable_pt_Rsqr _) = 2 * x. Proof. @@ -1042,28 +1200,8 @@ Proof. apply derivable_pt_lim_Rsqr. Qed. -Lemma derive_pt_comp : - forall f1 f2 (x:R) (pr1:derivable_pt f1 x) (pr2:derivable_pt f2 (f1 x)), - derive_pt (f2 o f1) x (derivable_pt_comp _ _ _ pr1 pr2) = - derive_pt f2 (f1 x) pr2 * derive_pt f1 x pr1. -Proof. - intros. - assert (H := derivable_derive f1 x pr1). - assert (H0 := derivable_derive f2 (f1 x) pr2). - assert - (H1 := derivable_derive (f2 o f1)%F x (derivable_pt_comp _ _ _ pr1 pr2)). - elim H; clear H; intros l1 H. - elim H0; clear H0; intros l2 H0. - elim H1; clear H1; intros l H1. - rewrite H; rewrite H0; apply derive_pt_eq_0. - assert (H3 := proj2_sig pr1). - unfold derive_pt in H; rewrite H in H3. - assert (H4 := proj2_sig pr2). - unfold derive_pt in H0; rewrite H0 in H4. - apply derivable_pt_lim_comp; assumption. -Qed. +(** ** Definition and derivative of power function with natural number exponent *) -(* Pow *) Definition pow_fct (n:nat) (y:R) : R := y ^ n. Lemma derivable_pt_lim_pow_pos : @@ -1141,6 +1279,8 @@ Proof. apply derivable_pt_lim_pow. Qed. +(** ** Irrelevance of derivability proof for derivative *) + Lemma pr_nu : forall f (x:R) (pr1 pr2:derivable_pt f x), derive_pt f x pr1 = derive_pt f x pr2. @@ -1149,6 +1289,16 @@ Proof. apply (uniqueness_limite f x x0 x1 H0 H1). Qed. +(** In dependently typed environments it is sometimes hard to rewrite. + Having pr_nu for separate x with a proof that they are equal helps. *) + +Lemma pr_nu_xeq : + forall f (x1 x2:R) (pr1:derivable_pt f x1) (pr2:derivable_pt f x2), + x1 = x2 -> derive_pt f x1 pr1 = derive_pt f x2 pr2. +Proof. + intros f x1 x2 H1 H2 Heq. + subst. apply pr_nu. +Qed. (************************************************************) (** * Local extremum's condition *) diff --git a/theories/Reals/Ranalysis5.v b/theories/Reals/Ranalysis5.v index 1713679c21..e73c73e8dd 100644 --- a/theories/Reals/Ranalysis5.v +++ b/theories/Reals/Ranalysis5.v @@ -219,7 +219,7 @@ intros f g lb ub f_incr_interv Hyp g_wf x x_encad. intro cond. apply Rlt_le ; apply f_incr_interv ; assumption. intro cond ; right ; rewrite cond ; reflexivity. assert (Hyp2:forall x, lb <= x <= ub -> f (g (f x)) = f x). - intros ; apply Hyp. apply f_incr_interv2 ; intuition. + intros ; apply Hyp. apply f_incr_interv2 ; intuition. apply f_incr_interv2 ; intuition. unfold comp ; unfold comp in Hyp. apply f_inj. @@ -279,8 +279,8 @@ Proof. intros. (* f x y f_cont_interv x_lt_y fx_neg fy_pos.*) cut (x <= y). intro. - generalize (dicho_lb_cv x y (fun z:R => cond_positivity (f z)) H3). - generalize (dicho_up_cv x y (fun z:R => cond_positivity (f z)) H3). + generalize (dicho_lb_cv x y (fun z:R => cond_positivity (f z)) H3). + generalize (dicho_up_cv x y (fun z:R => cond_positivity (f z)) H3). intros X X0. elim X; intros x0 p. elim X0; intros x1 p0. @@ -411,10 +411,10 @@ Qed. (* begin hide *) Ltac case_le H := - let t := type of H in - let h' := fresh in + let t := type of H in + let h' := fresh in match t with ?x <= ?y => case (total_order_T x y); - [intros h'; case h'; clear h' | + [intros h'; case h'; clear h' | intros h'; clear -H h'; elimtype False; lra ] end. (* end hide *) @@ -585,7 +585,7 @@ intros f g lb ub lb_lt_ub f_incr_interv f_eq_g f_cont_interv b b_encad. assert (x1_lt_x2 : x1 < x2). apply Rlt_trans with (r2:=x) ; assumption. assert (f_cont_myinterv : forall a : R, x1 <= a <= x2 -> continuity_pt f a). - intros ; apply f_cont_interv ; split. + intros ; apply f_cont_interv ; split. apply Rle_trans with (r2 := x1) ; intuition. apply Rle_trans with (r2 := x2) ; intuition. elim (f_interv_is_interv f x1 x2 y x1_lt_x2 Main f_cont_myinterv) ; intros x' Temp. @@ -708,7 +708,7 @@ intros f g lb ub x Prf g_cont_pur lb_lt_ub x_encad Prg_incr f_eq_g df_neq. rewrite l_null in Hl. apply df_neq. rewrite derive_pt_eq. - exact Hl. + exact Hl. elim (Hlinv' Premisse Premisse2 eps eps_pos). intros alpha cond. assert (alpha_pos := proj1 cond) ; assert (inv_cont := proj2 cond) ; clear cond. @@ -763,7 +763,7 @@ intros f g lb ub x Prf g_cont_pur lb_lt_ub x_encad Prg_incr f_eq_g df_neq. replace ((g (x + h) - g x) / h) with (1/ (h / (g (x + h) - g x))). assert (Hrewr : h = (comp f g ) (x+h) - (comp f g) x). rewrite f_eq_g. rewrite f_eq_g ; unfold id. rewrite Rplus_comm ; - unfold Rminus ; rewrite Rplus_assoc ; rewrite Rplus_opp_r. intuition. intuition. + unfold Rminus ; rewrite Rplus_assoc ; rewrite Rplus_opp_r. intuition. intuition. assumption. split ; [|intuition]. assert (Sublemma : forall x y z, - z <= y - x -> x <= y + z). @@ -791,7 +791,7 @@ intros f g lb ub x Prf g_cont_pur lb_lt_ub x_encad Prg_incr f_eq_g df_neq. rewrite f_eq_g. rewrite f_eq_g. unfold id ; rewrite Rplus_comm ; unfold Rminus ; rewrite Rplus_assoc ; rewrite Rplus_opp_r ; intuition. assumption. assumption. - rewrite Hrewr at 1. + rewrite Hrewr at 1. unfold comp. replace (g(x+h)) with (g x + (g (x+h) - g(x))) by field. pose (h':=g (x+h) - g x). @@ -811,7 +811,7 @@ intros f g lb ub x Prf g_cont_pur lb_lt_ub x_encad Prg_incr f_eq_g df_neq. apply inv_cont. split. exact h'_neq. - rewrite Rminus_0_r. + rewrite Rminus_0_r. unfold continuity_pt, continue_in, limit1_in, limit_in in g_cont_pur. elim (g_cont_pur mydelta mydelta_pos). intros delta3 cond3. @@ -830,7 +830,7 @@ intros f g lb ub x Prf g_cont_pur lb_lt_ub x_encad Prg_incr f_eq_g df_neq. intro Hfalse ; apply h_neq. apply (Rplus_0_r_uniq x). symmetry ; assumption. - replace (x + h - x) with h by field. + replace (x + h - x) with h by field. apply Rlt_le_trans with (r2:=delta''). assumption ; unfold delta''. intuition. apply Rle_trans with (r2:=mydelta''). apply Req_le. unfold delta''. intuition. @@ -863,25 +863,28 @@ exists (1 / derive_pt f (g x) (Prf (g x) Prg_incr)). apply derivable_pt_lim_recip_interv ; assumption. Qed. -Lemma derivable_pt_recip_interv_prelim1 :forall (f g:R->R) (lb ub x : R), +Lemma derivable_pt_recip_interv_prelim1 : forall (f g:R->R) (lb ub x : R), lb < ub -> f lb < x < f ub -> - (forall x : R, f lb <= x -> x <= f ub -> comp f g x = id x) -> (forall x : R, f lb <= x -> x <= f ub -> lb <= g x <= ub) -> - (forall x y : R, lb <= x -> x < y -> y <= ub -> f x < f y) -> (forall a : R, lb <= a <= ub -> derivable_pt f a) -> derivable_pt f (g x). Proof. -intros f g lb ub x lb_lt_ub x_encad f_eq_g g_ok f_incr f_derivable. - apply f_derivable. - assert (Left_inv := leftinv_is_rightinv_interv f g lb ub f_incr f_eq_g g_ok). - replace lb with ((comp g f) lb). - replace ub with ((comp g f) ub). - unfold comp. - assert (Temp:= f_incr_implies_g_incr_interv f g lb ub lb_lt_ub f_incr f_eq_g g_ok). - split ; apply Rlt_le ; apply Temp ; intuition. - apply Left_inv ; intuition. - apply Left_inv ; intuition. + intros f g lb ub x lb_lt_ub x_encad g_wf f_deriv. + apply f_deriv. + apply g_wf; lra. +Qed. + +Lemma derivable_pt_recip_interv_prelim1_decr : forall (f g:R->R) (lb ub x : R), + lb < ub -> + f ub < x < f lb -> + (forall x : R, f ub <= x -> x <= f lb -> lb <= g x <= ub) -> + (forall a : R, lb <= a <= ub -> derivable_pt f a) -> + derivable_pt f (g x). +Proof. + intros f g lb ub x lb_lt_ub x_encad g_wf f_deriv. + apply f_deriv. + apply g_wf; lra. Qed. Lemma derivable_pt_recip_interv : forall (f g:R->R) (lb ub x : R) @@ -892,7 +895,7 @@ Lemma derivable_pt_recip_interv : forall (f g:R->R) (lb ub x : R) (f_derivable:forall a : R, lb <= a <= ub -> derivable_pt f a), derive_pt f (g x) (derivable_pt_recip_interv_prelim1 f g lb ub x lb_lt_ub - x_encad f_eq_g g_wf f_incr f_derivable) + x_encad g_wf f_derivable) <> 0 -> derivable_pt g x. Proof. @@ -916,8 +919,54 @@ intros f g lb ub x lb_lt_ub x_encad f_eq_g g_wf f_incr f_derivable Df_neq. exact (proj1 x_encad). exact (proj2 x_encad). apply f_incr ; intuition. assumption. intros x0 x0_encad ; apply f_eq_g ; intuition. - rewrite pr_nu_var2_interv with (g:=f) (lb:=lb) (ub:=ub) (pr2:=derivable_pt_recip_interv_prelim1 f g lb ub x lb_lt_ub x_encad - f_eq_g g_wf f_incr f_derivable) ; [| |rewrite g_eq_f in g_incr ; rewrite g_eq_f in g_incr| ] ; intuition. + rewrite pr_nu_var2_interv with (g:=f) (lb:=lb) (ub:=ub) + (pr2:=derivable_pt_recip_interv_prelim1 f g lb ub x lb_lt_ub x_encad g_wf f_derivable); + [| |rewrite g_eq_f in g_incr ; rewrite g_eq_f in g_incr| ] ; intuition. +Qed. + +Lemma derivable_pt_recip_interv_decr : forall (f g:R->R) (lb ub x : R) + (lb_lt_ub:lb < ub) + (x_encad:f ub < x < f lb) + (f_eq_g:forall x : R, f ub <= x -> x <= f lb -> comp f g x = id x) + (g_wf:forall x : R, f ub <= x -> x <= f lb -> lb <= g x <= ub) + (f_decr:forall x y : R, lb <= x -> x < y -> y <= ub -> f y < f x) + (f_derivable:forall a : R, lb <= a <= ub -> derivable_pt f a), + derive_pt f (g x) + (derivable_pt_recip_interv_prelim1_decr f g lb ub x lb_lt_ub + x_encad g_wf f_derivable) + <> 0 -> + derivable_pt g x. +Proof. + intros. + apply derivable_pt_opp_rev. + unshelve eapply (derivable_pt_recip_interv (mirr_fct f) (opp_fct g) (-ub) (-lb) (x)). +- lra. +- unfold mirr_fct; repeat rewrite Ropp_involutive; lra. +- intros x0 H1 H2. + unfold mirr_fct in H1,H2; unfold opp_fct. + rewrite Ropp_involutive in H1,H2. + pose proof g_wf x0 as g_wfs; lra. +- intros x0 H1. + apply derivable_pt_mirr, f_derivable; lra. +- intros x0 H1 H2. + unfold mirr_fct in H1,H2 |-*; unfold opp_fct, comp. + rewrite Ropp_involutive in H1,H2 |-*. + apply f_eq_g; lra. +- intros x0 y0 H1 H2 H3. + unfold mirr_fct. + apply f_decr; lra. +- (* In order to rewrite with derive_pt_mirr the term must have the form + derive_pt (mirr_fct f) _ (derivable_pt_mirr ... + pr_nu is a sort of proof irrelevance lemma for derive_pt equalities *) + unshelve erewrite (pr_nu _ _ _). + + apply derivable_pt_mirr. + unfold opp_fct; rewrite Ropp_involutive. + apply f_derivable; apply g_wf; lra. + + rewrite derive_pt_mirr. + unfold opp_fct; rewrite Ropp_involutive. + match goal with H:context[derive_pt _ _ ?pr] |- _ => rewrite (pr_nu f (g x) _ pr) end. + apply Ropp_neq_0_compat. + assumption. Qed. (****************************************************) @@ -937,8 +986,8 @@ intros f g lb ub x Prf Prg lb_lt_ub x_encad local_recip Df_neq. ((derive_pt g x Prg) * (derive_pt f (g x) Prf) * / (derive_pt f (g x) Prf)). unfold Rdiv. rewrite (Rmult_comm _ (/ derive_pt f (g x) Prf)). - rewrite (Rmult_comm _ (/ derive_pt f (g x) Prf)). - apply Rmult_eq_compat_l. + rewrite (Rmult_comm _ (/ derive_pt f (g x) Prf)). + apply Rmult_eq_compat_l. rewrite Rmult_comm. rewrite <- derive_pt_comp. assert (x_encad2 : lb <= x <= ub) by intuition. @@ -948,7 +997,7 @@ intros f g lb ub x Prf Prg lb_lt_ub x_encad local_recip Df_neq. assumption. Qed. -Lemma derive_pt_recip_interv_prelim1_0 : forall (f g:R->R) (lb ub x:R), +Lemma derive_pt_recip_interv_prelim1_0 : forall (f g:R->R) (lb ub x:R), lb < ub -> f lb < x < f ub -> (forall x y : R, lb <= x -> x < y -> y <= ub -> f x < f y) -> @@ -967,7 +1016,7 @@ intros f g lb ub x lb_lt_ub x_encad f_incr g_wf f_eq_g. intuition. Qed. -Lemma derive_pt_recip_interv_prelim1_1 : forall (f g:R->R) (lb ub x:R), +Lemma derive_pt_recip_interv_prelim1_1 : forall (f g:R->R) (lb ub x:R), lb < ub -> f lb < x < f ub -> (forall x y : R, lb <= x -> x < y -> y <= ub -> f x < f y) -> @@ -980,6 +1029,32 @@ intros f g lb ub x lb_lt_ub x_encad f_incr g_wf f_eq_g. split ; apply Rlt_le ; intuition. Qed. +Lemma derive_pt_recip_interv_prelim1_1_decr : forall (f g:R->R) (lb ub x:R), + lb < ub -> + f ub < x < f lb -> + (forall x y : R, lb <= x -> x < y -> y <= ub -> f y < f x) -> + (forall x : R, f ub <= x -> x <= f lb -> lb <= g x <= ub) -> + (forall x, f ub <= x -> x <= f lb -> (comp f g) x = id x) -> + lb <= g x <= ub. +Proof. + intros f g lb ub x lb_lt_ub x_encad f_decr g_wf f_eq_g. + enough (-ub <= - g x <= - lb) by lra. + unshelve eapply (derive_pt_recip_interv_prelim1_1 (mirr_fct f) (opp_fct g) (-ub) (-lb) (x)). +- lra. +- unfold mirr_fct; repeat rewrite Ropp_involutive; lra. +- intros x0 y0 H1 H2 H3. + unfold mirr_fct. + apply f_decr; lra. +- intros x0 H1 H2. + unfold mirr_fct in H1,H2; unfold opp_fct. + rewrite Ropp_involutive in H1,H2. + pose proof g_wf x0 as g_wfs; lra. +- intros x0 H1 H2. + unfold mirr_fct in H1,H2 |-*; unfold opp_fct, comp. + rewrite Ropp_involutive in H1,H2 |-*. + apply f_eq_g; lra. +Qed. + Lemma derive_pt_recip_interv : forall (f g:R->R) (lb ub x:R) (lb_lt_ub:lb < ub) (x_encad:f lb < x < f ub) (f_incr:forall x y : R, lb <= x -> x < y -> y <= ub -> f x < f y) @@ -987,7 +1062,7 @@ Lemma derive_pt_recip_interv : forall (f g:R->R) (lb ub x:R) (Prf:forall a : R, lb <= a <= ub -> derivable_pt f a) (f_eq_g:forall x, f lb <= x -> x <= f ub -> (comp f g) x = id x) (Df_neq:derive_pt f (g x) (derivable_pt_recip_interv_prelim1 f g lb ub x - lb_lt_ub x_encad f_eq_g g_wf f_incr Prf) <> 0), + lb_lt_ub x_encad g_wf Prf) <> 0), derive_pt g x (derivable_pt_recip_interv f g lb ub x lb_lt_ub x_encad f_eq_g g_wf f_incr Prf Df_neq) = @@ -1005,7 +1080,75 @@ intros. [intuition | intuition | | intuition]. exact (derive_pt_recip_interv_prelim1_0 f g lb ub x lb_lt_ub x_encad f_incr g_wf f_eq_g). Qed. - + +Lemma derive_pt_recip_interv_decr : forall (f g:R->R) (lb ub x:R) + (lb_lt_ub:lb < ub) + (x_encad:f ub < x < f lb) + (f_decr:forall x y : R, lb <= x -> x < y -> y <= ub -> f y < f x) + (g_wf:forall x : R, f ub <= x -> x <= f lb -> lb <= g x <= ub) + (Prf:forall a : R, lb <= a <= ub -> derivable_pt f a) + (f_eq_g:forall x, f ub <= x -> x <= f lb -> (comp f g) x = id x) + (Df_neq:derive_pt f (g x) (derivable_pt_recip_interv_prelim1_decr f g lb ub x + lb_lt_ub x_encad g_wf Prf) <> 0), + derive_pt g x (derivable_pt_recip_interv_decr f g lb ub x lb_lt_ub x_encad f_eq_g + g_wf f_decr Prf Df_neq) + = + 1 / (derive_pt f (g x) (Prf (g x) (derive_pt_recip_interv_prelim1_1_decr f g lb ub x + lb_lt_ub x_encad f_decr g_wf f_eq_g))). +Proof. + (* This proof based on derive_pt_recip_interv looks fairly long compared to the direct proof above, + but the direct proof needs a lot of lengthy preparation lemmas e.g. derivable_pt_lim_recip_interv. *) + intros. + (* Note: here "unshelve epose" with proving the premises first does not work. + The more abstract form with the unbound evars has less issues with dependent rewriting. *) + epose proof (derive_pt_recip_interv (mirr_fct f) (opp_fct g) (-ub) (-lb) (x) _ _ _ _ _ _ _). + rewrite derive_pt_mirr_rev in H. + rewrite derive_pt_opp_rev in H. + unfold opp_fct in H. + match goal with + | H:context[derive_pt ?f ?x1 ?pr1] |- context[derive_pt ?f ?x2 ?pr2] => + rewrite (pr_nu_xeq f x1 x2 pr1 pr2 (Ropp_involutive x2)) in H + end. + match goal with + | H:context[derive_pt ?f ?x ?pr1] |- context[derive_pt ?f ?x ?pr2] => + rewrite (pr_nu f x pr1 pr2) in H + end. + apply Ropp_eq_compat in H; rewrite Ropp_involutive in H. + rewrite H; field. + pose proof Df_neq as Df_neq'. + match goal with + | H:context[derive_pt ?f ?x ?pr1] |- context[derive_pt ?f ?x ?pr2] => + rewrite (pr_nu f x pr1 pr2) in H + end. + assumption. + +Unshelve. +- abstract lra. +- unfold mirr_fct; repeat rewrite Ropp_involutive; abstract lra. +- intros x0 y0 H1 H2 H3. + unfold mirr_fct. + apply f_decr; abstract lra. +- intros x0 H1 H2. + unfold mirr_fct in H1,H2; unfold opp_fct. + rewrite Ropp_involutive in H1,H2. + pose proof g_wf x0 as g_wfs; abstract lra. +- intros x0 H1. + apply derivable_pt_mirr, Prf; abstract lra. +- intros x0 H1 H2. + unfold mirr_fct in H1,H2 |-*; unfold opp_fct, comp. + rewrite Ropp_involutive in H1,H2 |-*. + apply f_eq_g; abstract lra. +- unshelve erewrite (pr_nu _ _ _). + apply derivable_pt_mirr. + unfold opp_fct; rewrite Ropp_involutive. + apply Prf; apply g_wf; abstract lra. + rewrite derive_pt_mirr. + unfold opp_fct; rewrite Ropp_involutive. + apply Ropp_neq_0_compat. + erewrite (pr_nu _ _ _). + apply Df_neq. +Qed. + (****************************************************) (** * Existence of the derivative of a function which is the limit of a sequence of functions *) (****************************************************) @@ -1105,7 +1248,7 @@ assert (Main : Rabs ((f (x+h) - fn N (x+h)) - (f x - fn N x) + (fn N (x+h) - fn Rabs h * Rabs (fn' N c - g c) + Rabs h * Rabs (g c - g x)). rewrite Rplus_assoc ; rewrite Rplus_assoc ; rewrite Rplus_assoc ; apply Rplus_le_compat_l ; apply Rplus_le_compat_l ; - rewrite <- Rmult_plus_distr_l ; apply Rmult_le_compat_l. + rewrite <- Rmult_plus_distr_l ; apply Rmult_le_compat_l. solve[apply Rabs_pos]. solve[apply Rabs_triang]. apply Rlt_trans with (Rabs h * eps / 4 + Rabs h * eps / 4 + @@ -1129,7 +1272,7 @@ assert (Main : Rabs ((f (x+h) - fn N (x+h)) - (f x - fn N x) + (fn N (x+h) - fn solve[unfold no_cond ; intuition]. apply Rgt_not_eq ; exact (proj2 P). apply Rlt_trans with (Rabs h). - apply Rabs_def1. + apply Rabs_def1. apply Rlt_trans with 0. destruct P; lra. apply Rabs_pos_lt ; assumption. @@ -1142,7 +1285,7 @@ assert (Main : Rabs ((f (x+h) - fn N (x+h)) - (f x - fn N x) + (fn N (x+h) - fn rewrite Rplus_assoc ; rewrite Rplus_assoc ; rewrite <- Rmult_plus_distr_l. replace (Rabs h * eps / 4 + (Rabs h * eps / 4 + Rabs h * (eps / 8 + eps / 8))) with (Rabs h * (eps / 4 + eps / 4 + eps / 8 + eps / 8)) by field. - apply Rmult_lt_compat_l. + apply Rmult_lt_compat_l. apply Rabs_pos_lt ; assumption. lra. assert (H := pr1 c P) ; elim H ; clear H ; intros l Hl. @@ -1211,7 +1354,7 @@ assert (Main : Rabs ((f (x+h) - fn N (x+h)) - (f x - fn N x) + (fn N (x+h) - fn Rabs h * Rabs (fn' N c - g c) + Rabs h * Rabs (g c - g x)). rewrite Rplus_assoc ; rewrite Rplus_assoc ; rewrite Rplus_assoc ; apply Rplus_le_compat_l ; apply Rplus_le_compat_l ; - rewrite <- Rmult_plus_distr_l ; apply Rmult_le_compat_l. + rewrite <- Rmult_plus_distr_l ; apply Rmult_le_compat_l. solve[apply Rabs_pos]. solve[apply Rabs_triang]. apply Rlt_trans with (Rabs h * eps / 4 + Rabs h * eps / 4 + @@ -1247,7 +1390,7 @@ assert (Main : Rabs ((f (x+h) - fn N (x+h)) - (f x - fn N x) + (fn N (x+h) - fn rewrite Rplus_assoc ; rewrite Rplus_assoc ; rewrite <- Rmult_plus_distr_l. replace (Rabs h * eps / 4 + (Rabs h * eps / 4 + Rabs h * (eps / 8 + eps / 8))) with (Rabs h * (eps / 4 + eps / 4 + eps / 8 + eps / 8)) by field. - apply Rmult_lt_compat_l. + apply Rmult_lt_compat_l. apply Rabs_pos_lt ; assumption. lra. assert (H := pr1 c P) ; elim H ; clear H ; intros l Hl. @@ -1270,7 +1413,7 @@ assert (Main : Rabs ((f (x+h) - fn N (x+h)) - (f x - fn N x) + (fn N (x+h) - fn apply uniqueness_limite with (f:= fn N) (x:=c) ; assumption. rewrite Main ; reflexivity. reflexivity. - replace ((f (x + h) - f x) / h - g x) with ((/h) * ((f (x + h) - f x) - h * g x)). + replace ((f (x + h) - f x) / h - g x) with ((/h) * ((f (x + h) - f x) - h * g x)). rewrite Rabs_mult ; rewrite Rabs_Rinv. replace eps with (/ Rabs h * (Rabs h * eps)). apply Rmult_lt_compat_l. diff --git a/theories/Reals/Ratan.v b/theories/Reals/Ratan.v index a6d053b80d..361bea6e85 100644 --- a/theories/Reals/Ratan.v +++ b/theories/Reals/Ratan.v @@ -12,6 +12,7 @@ Require Import Lra. Require Import Rbase. Require Import PSeries_reg. Require Import Rtrigo1. +Require Import Rtrigo_facts. Require Import Ranalysis_reg. Require Import Rfunctions. Require Import AltSeries. @@ -24,26 +25,21 @@ Require Import Lia. Local Open Scope R_scope. -(** Tools *) +(*********************************************************) +(** * Preliminaries *) +(*********************************************************) -Lemma Ropp_div : forall x y, -x/y = -(x/y). -Proof. -intros x y; unfold Rdiv; rewrite <-Ropp_mult_distr_l_reverse; reflexivity. -Qed. - -Definition pos_half_prf : 0 < /2. -Proof. lra. Qed. +(** ** Various generic lemmas which probably should go somewhere else *) -Definition pos_half := mkposreal (/2) pos_half_prf. - -Lemma Boule_half_to_interval : - forall x , Boule (/2) pos_half x -> 0 <= x <= 1. +Lemma Boule_half_to_interval : forall x, + Boule (/2) posreal_half x -> 0 <= x <= 1. Proof. -unfold Boule, pos_half; simpl. +unfold Boule, posreal_half; simpl. intros x b; apply Rabs_def2 in b; destruct b; split; lra. Qed. -Lemma Boule_lt : forall c r x, Boule c r x -> Rabs x < Rabs c + r. +Lemma Boule_lt : forall c r x, + Boule c r x -> Rabs x < Rabs c + r. Proof. unfold Boule; intros c r x h. apply Rabs_def2 in h; destruct h; apply Rabs_def1; @@ -52,9 +48,10 @@ apply Rabs_def2 in h; destruct h; apply Rabs_def1; Qed. (* The following lemma does not belong here. *) -Lemma Un_cv_ext : - forall un vn, (forall n, un n = vn n) -> - forall l, Un_cv un l -> Un_cv vn l. +Lemma Un_cv_ext : forall un vn, + (forall n, un n = vn n) -> + forall l, Un_cv un l -> + Un_cv vn l. Proof. intros un vn quv l P eps ep; destruct (P eps ep) as [N Pn]; exists N. intro n; rewrite <- quv; apply Pn. @@ -62,7 +59,7 @@ Qed. (* The following two lemmas are general purposes about alternated series. They do not belong here. *) -Lemma Alt_first_term_bound :forall f l N n, +Lemma Alt_first_term_bound : forall f l N n, Un_decreasing f -> Un_cv f 0 -> Un_cv (sum_f_R0 (tg_alt f)) l -> (N <= n)%nat -> @@ -87,7 +84,7 @@ intros [ | N] Npos n decr to0 cv nN. (sum_f_R0 (tg_alt (fun i => ((-1) ^ S N * f(S N + i)%nat)))) (l - sum_f_R0 (tg_alt f) N)). intros eps ep; destruct (cv eps ep) as [M PM]; exists M. - intros n' nM. + intros n' nM. match goal with |- ?C => set (U := C) end. assert (nM' : (n' + S N >= M)%nat) by lia. generalize (PM _ nM'); unfold R_dist. @@ -102,7 +99,7 @@ intros [ | N] Npos n decr to0 cv nN. lia. assert (cv'' : Un_cv (sum_f_R0 (tg_alt (fun i => f (S N + i)%nat))) ((-1) ^ S N * (l - sum_f_R0 (tg_alt f) N))). - apply (Un_cv_ext (fun n => (-1) ^ S N * + apply (Un_cv_ext (fun n => (-1) ^ S N * sum_f_R0 (tg_alt (fun i : nat => (-1) ^ S N * f (S N + i)%nat)) n)). intros n0; rewrite scal_sum; apply sum_eq; intros i _. unfold tg_alt; ring_simplify; replace (((-1) ^ S N) ^ 2) with 1. @@ -122,7 +119,7 @@ intros [ | N] Npos n decr to0 cv nN. assert (t := decreasing_prop _ _ _ (CV_ALT_step1 f decr) dist). apply Rle_trans with (sum_f_R0 (tg_alt f) (2 * p) - l). unfold Rminus; apply Rplus_le_compat_r; exact t. - match goal with _ : ?a <= l, _ : l <= ?b |- _ => + match goal with _ : ?a <= l, _ : l <= ?b |- _ => replace (f (S (2 * p))) with (b - a) by (rewrite tech5; unfold tg_alt; rewrite pow_1_odd; ring); lra end. @@ -171,15 +168,15 @@ solve[apply decr]. Qed. Lemma Alt_CVU : forall (f : nat -> R -> R) g h c r, - (forall x, Boule c r x ->Un_decreasing (fun n => f n x)) -> + (forall x, Boule c r x ->Un_decreasing (fun n => f n x)) -> (forall x, Boule c r x -> Un_cv (fun n => f n x) 0) -> - (forall x, Boule c r x -> + (forall x, Boule c r x -> Un_cv (sum_f_R0 (tg_alt (fun i => f i x))) (g x)) -> (forall x n, Boule c r x -> f n x <= h n) -> (Un_cv h 0) -> CVU (fun N x => sum_f_R0 (tg_alt (fun i => f i x)) N) g c r. Proof. -intros f g h c r decr to0 to_g bound bound0 eps ep. +intros f g h c r decr to0 to_g bound bound0 eps ep. assert (ep' : 0 <eps/2) by lra. destruct (bound0 _ ep) as [N Pn]; exists N. intros n y nN dy. @@ -192,10 +189,10 @@ generalize (Pn _ nN); unfold R_dist; rewrite Rminus_0_r; intros t. apply Rabs_def2 in t; tauto. Qed. -(* The following lemmas are general purpose lemmas about squares. +(* The following lemmas are general purpose lemmas about squares. They do not belong here *) -Lemma pow2_ge_0 : forall x, 0 <= x ^ 2. +Lemma pow2_ge_0 : forall x, 0 <= x^2. Proof. intros x; destruct (Rle_lt_dec 0 x). replace (x ^ 2) with (x * x) by field. @@ -204,26 +201,29 @@ intros x; destruct (Rle_lt_dec 0 x). apply Rmult_le_pos; lra. Qed. -Lemma pow2_abs : forall x, Rabs x ^ 2 = x ^ 2. +Lemma pow2_abs : forall x, Rabs x^2 = x^2. Proof. intros x; destruct (Rle_lt_dec 0 x). rewrite Rabs_pos_eq;[field | assumption]. rewrite <- Rabs_Ropp, Rabs_pos_eq;[field | lra]. Qed. -(** * Properties of tangent *) +(** ** Properties of tangent *) + +(** *** Derivative of tangent *) -Lemma derivable_pt_tan : forall x, -PI/2 < x < PI/2 -> derivable_pt tan x. +Lemma derivable_pt_tan : forall x, -PI/2 < x < PI/2 -> + derivable_pt tan x. Proof. intros x xint. - unfold derivable_pt, tan. + unfold derivable_pt, tan. apply derivable_pt_div ; [reg | reg | ]. apply Rgt_not_eq. unfold Rgt ; apply cos_gt_0; [unfold Rdiv; rewrite <- Ropp_mult_distr_l_reverse; fold (-PI/2) |];tauto. Qed. -Lemma derive_pt_tan : forall (x:R), +Lemma derive_pt_tan : forall x, forall (Pr1: -PI/2 < x < PI/2), derive_pt tan x (derivable_pt_tan x Pr1) = 1 + (tan x)^2. Proof. @@ -233,15 +233,15 @@ assert (cos x <> 0). unfold tan; reg; unfold pow, Rsqr; field; assumption. Qed. -(** Proof that tangent is a bijection *) +(** *** Proof that tangent is a bijection *) + (* to be removed? *) -Lemma derive_increasing_interv : - forall (a b:R) (f:R -> R), - a < b -> - forall (pr:forall x, a < x < b -> derivable_pt f x), - (forall t:R, forall (t_encad : a < t < b), 0 < derive_pt f t (pr t t_encad)) -> - forall x y:R, a < x < b -> a < y < b -> x < y -> f x < f y. +Lemma derive_increasing_interv : forall (a b : R) (f : R -> R), + a < b -> + forall (pr:forall x, a < x < b -> derivable_pt f x), + (forall t:R, forall (t_encad : a < t < b), 0 < derive_pt f t (pr t t_encad)) -> + forall x y:R, a < x < b -> a < y < b -> x < y -> f x < f y. Proof. intros a b f a_lt_b pr Df_gt_0 x y x_encad y_encad x_lt_y. assert (derivable_id_interv : forall c : R, x < c < y -> derivable_pt id c). @@ -255,7 +255,7 @@ intros a b f a_lt_b pr Df_gt_0 x y x_encad y_encad x_lt_y. apply Rlt_le_trans with (r2:=x) ; [exact (proj1 x_encad) | exact (proj1 c_encad)]. apply Rle_lt_trans with (r2:=y) ; [ exact (proj2 c_encad) | exact (proj2 y_encad)]. assert (id_cont_interv : forall c : R, x <= c <= y -> continuity_pt id c). - intros ; apply derivable_continuous_pt ; apply derivable_pt_id. + intros ; apply derivable_continuous_pt ; apply derivable_pt_id. elim (MVT f id x y derivable_f_interv derivable_id_interv x_lt_y f_cont_interv id_cont_interv). intros c Temp ; elim Temp ; clear Temp ; intros Pr eq. replace (id y - id x) with (y - x) in eq by intuition. @@ -296,8 +296,7 @@ Qed. (* The following lemmas about PI should probably be in Rtrigo. *) -Lemma PI2_lower_bound : - forall x, 0 < x < 2 -> 0 < cos x -> x < PI/2. +Lemma PI2_lower_bound : forall x, 0 < x < 2 -> 0 < cos x -> x < PI/2. Proof. intros x [xp xlt2] cx. destruct (Rtotal_order x (PI/2)) as [xltpi2 | [xeqpi2 | xgtpi2]]. @@ -305,7 +304,7 @@ destruct (Rtotal_order x (PI/2)) as [xltpi2 | [xeqpi2 | xgtpi2]]. now case (Rgt_not_eq _ _ cx); rewrite xeqpi2, cos_PI2. destruct (MVT_cor1 cos (PI/2) x derivable_cos xgtpi2) as [c [Pc [cint1 cint2]]]. -revert Pc; rewrite cos_PI2, Rminus_0_r. +revert Pc; rewrite cos_PI2, Rminus_0_r. rewrite <- (pr_nu cos c (derivable_pt_cos c)), derive_pt_cos. assert (0 < c < 2) by (split; assert (t := PI2_RGT_0); lra). assert (0 < sin c) by now apply sin_pos_tech. @@ -330,18 +329,16 @@ Qed. Lemma PI2_1 : 1 < PI/2. Proof. assert (t := PI2_3_2); lra. Qed. -Lemma tan_increasing : - forall x y:R, - -PI/2 < x -> - x < y -> - y < PI/2 -> tan x < tan y. +Lemma tan_increasing : forall x y, + -PI/2 < x -> x < y -> y < PI/2 -> + tan x < tan y. Proof. intros x y Z_le_x x_lt_y y_le_1. assert (x_encad : -PI/2 < x < PI/2). split ; [assumption | apply Rlt_trans with (r2:=y) ; assumption]. assert (y_encad : -PI/2 < y < PI/2). split ; [apply Rlt_trans with (r2:=x) ; intuition | intuition ]. - assert (local_derivable_pt_tan : forall x : R, -PI/2 < x < PI/2 -> + assert (local_derivable_pt_tan : forall x, -PI/2 < x < PI/2 -> derivable_pt tan x). intros ; apply derivable_pt_tan ; intuition. apply derive_increasing_interv with (a:=-PI/2) (b:=PI/2) (pr:=local_derivable_pt_tan) ; intuition. @@ -352,8 +349,11 @@ intros x y Z_le_x x_lt_y y_le_1. apply plus_Rsqr_gt_0. Qed. -Lemma tan_is_inj : forall x y, -PI/2 < x < PI/2 -> -PI/2 < y < PI/2 -> - tan x = tan y -> x = y. + +Lemma tan_inj : forall x y, + -PI/2 < x < PI/2 -> -PI/2 < y < PI/2 -> + tan x = tan y -> + x = y. Proof. intros a b a_encad b_encad fa_eq_fb. case(total_order_T a b). @@ -366,9 +366,12 @@ Proof. case (Rlt_not_eq (tan b) (tan a)) ; [|symmetry] ; assumption. Qed. -Lemma exists_atan_in_frame : - forall lb ub y, lb < ub -> -PI/2 < lb -> ub < PI/2 -> - tan lb < y < tan ub -> {x | lb < x < ub /\ tan x = y}. +Notation tan_is_inj := tan_inj (only parsing). (* compat *) + +Lemma exists_atan_in_frame : forall lb ub y, + lb < ub -> -PI/2 < lb -> ub < PI/2 -> + tan lb < y < tan ub -> + {x | lb < x < ub /\ tan x = y}. Proof. intros lb ub y lb_lt_ub lb_cond ub_cond y_encad. case y_encad ; intros y_encad1 y_encad2. @@ -384,9 +387,9 @@ intros lb ub y lb_lt_ub lb_cond ub_cond y_encad. assumption. intros x x_cond. replace (tan x - y - (tan a - y)) with (tan x - tan a) by field. exact (Temp x x_cond). - assert (H1 : (fun x : R => tan x - y) lb < 0). + assert (H1 : (fun x => tan x - y) lb < 0). apply Rlt_minus. assumption. - assert (H2 : 0 < (fun x : R => tan x - y) ub). + assert (H2 : 0 < (fun x => tan x - y) ub). apply Rgt_minus. assumption. destruct (IVT_interv (fun x => tan x - y) lb ub Cont lb_lt_ub H1 H2) as (x,Hx). exists x. @@ -409,7 +412,12 @@ intros lb ub y lb_lt_ub lb_cond ub_cond y_encad. case H4 ; intuition. Qed. -(** * Definition of arctangent as the reciprocal function of tangent and proof of this status *) +(*********************************************************) +(** * Definition of arctangent *) +(*********************************************************) + +(** ** Definition of arctangent as the reciprocal function of tangent and proof of this status *) + Lemma tan_1_gt_1 : tan 1 > 1. Proof. assert (0 < cos 1) by (apply cos_gt_0; assert (t:=PI2_1); lra). @@ -516,7 +524,7 @@ split. apply Rgt_not_eq; assumption. unfold tan. set (u' := PI / 2); unfold Rdiv; apply Rmult_lt_compat_r; unfold u'. - apply Rinv_0_lt_compat. + apply Rinv_0_lt_compat. rewrite cos_shift; assumption. assert (vlt3 : u < /4). replace (/4) with (/2 * /2) by field. @@ -565,25 +573,31 @@ Qed. Definition atan x := let (v, _) := pre_atan x in v. -Lemma atan_bound : forall x, -PI/2 < atan x < PI/2. +Lemma atan_bound : forall x, + -PI/2 < atan x < PI/2. Proof. intros x; unfold atan; destruct (pre_atan x) as [v [int _]]; exact int. Qed. -Lemma atan_right_inv : forall x, tan (atan x) = x. +Lemma tan_atan : forall x, + tan (atan x) = x. Proof. intros x; unfold atan; destruct (pre_atan x) as [v [_ q]]; exact q. Qed. -Lemma atan_opp : forall x, atan (- x) = - atan x. +Notation atan_right_inv := tan_atan (only parsing). (* compat *) + +Lemma atan_opp : forall x, + atan (- x) = - atan x. Proof. intros x; generalize (atan_bound (-x)); rewrite Ropp_div;intros [a b]. generalize (atan_bound x); rewrite Ropp_div; intros [c d]. -apply tan_is_inj; try rewrite Ropp_div; try split; try lra. -rewrite tan_neg, !atan_right_inv; reflexivity. +apply tan_inj; try rewrite Ropp_div; try split; try lra. +rewrite tan_neg, !tan_atan; reflexivity. Qed. -Lemma derivable_pt_atan : forall x, derivable_pt atan x. +Lemma derivable_pt_atan : forall x, + derivable_pt atan x. Proof. intros x. destruct (frame_tan x) as [ub [[ub0 ubpi] P]]. @@ -591,22 +605,22 @@ assert (lb_lt_ub : -ub < ub) by apply pos_opp_lt, ub0. assert (xint : tan(-ub) < x < tan ub). assert (xint' : x < tan ub /\ -(tan ub) < x) by apply Rabs_def2, P. rewrite tan_neg; tauto. -assert (inv_p : forall x, tan(-ub) <= x -> x <= tan ub -> +assert (inv_p : forall x, tan(-ub) <= x -> x <= tan ub -> comp tan atan x = id x). - intros; apply atan_right_inv. + intros; apply tan_atan. assert (int_tan : forall y, tan (- ub) <= y -> y <= tan ub -> -ub <= atan y <= ub). clear -ub0 ubpi; intros y lo up; split. destruct (Rle_lt_dec (-ub) (atan y)) as [h | abs]; auto. assert (y < tan (-ub)). - rewrite <- (atan_right_inv y); apply tan_increasing. + rewrite <- (tan_atan y); apply tan_increasing. destruct (atan_bound y); assumption. assumption. lra. lra. destruct (Rle_lt_dec (atan y) ub) as [h | abs]; auto. assert (tan ub < y). - rewrite <- (atan_right_inv y); apply tan_increasing. + rewrite <- (tan_atan y); apply tan_increasing. rewrite Ropp_div; lra. assumption. destruct (atan_bound y); assumption. @@ -620,8 +634,8 @@ assert (der : forall a, -ub <= a <= ub -> derivable_pt tan a). intros a [la ua]; apply derivable_pt_tan. rewrite Ropp_div; split; lra. assert (df_neq : derive_pt tan (atan x) - (derivable_pt_recip_interv_prelim1 tan atan - (- ub) ub x lb_lt_ub xint inv_p int_tan incr der) <> 0). + (derivable_pt_recip_interv_prelim1 tan atan + (- ub) ub x lb_lt_ub xint int_tan der) <> 0). rewrite <- (pr_nu tan (atan x) (derivable_pt_tan (atan x) (atan_bound x))). rewrite derive_pt_tan. @@ -631,7 +645,8 @@ apply (derivable_pt_recip_interv tan atan (-ub) ub x exact df_neq. Qed. -Lemma atan_increasing : forall x y, x < y -> atan x < atan y. +Lemma atan_increasing : forall x y, + x < y -> atan x < atan y. Proof. intros x y d. assert (t1 := atan_bound x). @@ -640,7 +655,7 @@ destruct (Rlt_le_dec (atan x) (atan y)) as [lt | bad]. assumption. apply Rlt_not_le in d. case d. -rewrite <- (atan_right_inv y), <- (atan_right_inv x). +rewrite <- (tan_atan y), <- (tan_atan x). destruct bad as [ylt | yx]. apply Rlt_le, tan_increasing; try tauto. solve[rewrite yx; apply Rle_refl]. @@ -648,26 +663,80 @@ Qed. Lemma atan_0 : atan 0 = 0. Proof. -apply tan_is_inj; try (apply atan_bound). +apply tan_inj; try (apply atan_bound). assert (t := PI_RGT_0); rewrite Ropp_div; split; lra. -rewrite atan_right_inv, tan_0. +rewrite tan_atan, tan_0. reflexivity. Qed. +Lemma atan_eq0 : forall x, + atan x = 0 -> x = 0. +Proof. +intros x. +generalize (atan_increasing 0 x) (atan_increasing x 0). +rewrite atan_0. +lra. +Qed. + Lemma atan_1 : atan 1 = PI/4. Proof. assert (ut := PI_RGT_0). assert (-PI/2 < PI/4 < PI/2) by (rewrite Ropp_div; split; lra). assert (t := atan_bound 1). -apply tan_is_inj; auto. -rewrite tan_PI4, atan_right_inv; reflexivity. +apply tan_inj; auto. +rewrite tan_PI4, tan_atan; reflexivity. Qed. -(** atan's derivative value is the function 1 / (1+x²) *) +Lemma atan_tan : forall x, - (PI / 2) < x < PI / 2 -> + atan (tan x) = x. +Proof. +intros x xB. +apply tan_inj. +- now apply atan_bound. +- lra. +- now apply tan_atan. +Qed. + +Lemma atan_inv : forall x, (0 < x)%R -> + atan (/ x) = (PI / 2 - atan x)%R. +Proof. +intros x Hx. +apply tan_inj. +- apply atan_bound. +- split. + + apply Rlt_trans with R0. + * unfold Rdiv. + rewrite Ropp_mult_distr_l_reverse. + apply Ropp_lt_gt_0_contravar. + apply PI2_RGT_0. + * apply Rgt_minus. + apply atan_bound. + + apply Rplus_lt_reg_r with (atan x - PI / 2)%R. + ring_simplify. + rewrite <- atan_0. + now apply atan_increasing. +- rewrite tan_atan. + unfold tan. + rewrite sin_shift. + rewrite cos_shift. + rewrite <- Rinv_Rdiv. + + apply f_equal, sym_eq, tan_atan. + + apply Rgt_not_eq, sin_gt_0. + * rewrite <- atan_0. + now apply atan_increasing. + * apply Rlt_trans with (2 := PI2_Rlt_PI). + apply atan_bound. + + apply Rgt_not_eq, cos_gt_0. + unfold Rdiv. + rewrite <- Ropp_mult_distr_l_reverse. + apply atan_bound. + apply atan_bound. +Qed. + +(** ** Derivative of arctangent *) Lemma derive_pt_atan : forall x, - derive_pt atan x (derivable_pt_atan x) = - 1 / (1 + x²). + derive_pt atan x (derivable_pt_atan x) = 1 / (1 + x²). Proof. intros x. destruct (frame_tan x) as [ub [[ub0 ubpi] Pub]]. @@ -675,22 +744,22 @@ assert (lb_lt_ub : -ub < ub) by apply pos_opp_lt, ub0. assert (xint : tan(-ub) < x < tan ub). assert (xint' : x < tan ub /\ -(tan ub) < x) by apply Rabs_def2, Pub. rewrite tan_neg; tauto. -assert (inv_p : forall x, tan(-ub) <= x -> x <= tan ub -> +assert (inv_p : forall x, tan(-ub) <= x -> x <= tan ub -> comp tan atan x = id x). - intros; apply atan_right_inv. + intros; apply tan_atan. assert (int_tan : forall y, tan (- ub) <= y -> y <= tan ub -> -ub <= atan y <= ub). clear -ub0 ubpi; intros y lo up; split. destruct (Rle_lt_dec (-ub) (atan y)) as [h | abs]; auto. assert (y < tan (-ub)). - rewrite <- (atan_right_inv y); apply tan_increasing. + rewrite <- (tan_atan y); apply tan_increasing. destruct (atan_bound y); assumption. assumption. lra. lra. destruct (Rle_lt_dec (atan y) ub) as [h | abs]; auto. assert (tan ub < y). - rewrite <- (atan_right_inv y); apply tan_increasing. + rewrite <- (tan_atan y); apply tan_increasing. rewrite Ropp_div; lra. assumption. destruct (atan_bound y); assumption. @@ -704,8 +773,8 @@ assert (der : forall a, -ub <= a <= ub -> derivable_pt tan a). intros a [la ua]; apply derivable_pt_tan. rewrite Ropp_div; split; lra. assert (df_neq : derive_pt tan (atan x) - (derivable_pt_recip_interv_prelim1 tan atan - (- ub) ub x lb_lt_ub xint inv_p int_tan incr der) <> 0). + (derivable_pt_recip_interv_prelim1 tan atan + (- ub) ub x lb_lt_ub xint int_tan der) <> 0). rewrite <- (pr_nu tan (atan x) (derivable_pt_tan (atan x) (atan_bound x))). rewrite derive_pt_tan. @@ -716,14 +785,14 @@ rewrite <- (pr_nu atan x (derivable_pt_recip_interv tan atan (- ub) ub x lb_lt_ub xint inv_p int_tan incr der df_neq)). rewrite t. assert (t' := atan_bound x). -rewrite <- (pr_nu tan (atan x) (derivable_pt_tan _ t')). -rewrite derive_pt_tan, atan_right_inv. +rewrite <- (pr_nu tan (atan x) (derivable_pt_tan _ t')). +rewrite derive_pt_tan, tan_atan. replace (Rsqr x) with (x ^ 2) by (unfold Rsqr; ring). reflexivity. Qed. -Lemma derivable_pt_lim_atan : - forall x, derivable_pt_lim atan x (/(1 + x^2)). +Lemma derivable_pt_lim_atan : forall x, + derivable_pt_lim atan x (/ (1 + x^2)). Proof. intros x. apply derive_pt_eq_1 with (derivable_pt_atan x). @@ -732,12 +801,14 @@ rewrite <- (Rmult_1_l (Rinv _)). apply derive_pt_atan. Qed. -(** * Definition of the arctangent function as the sum of the arctan power series *) +(** ** Definition of the arctangent function as the sum of the arctan power series *) + (* Proof taken from Guillaume Melquiond's interval package for Coq *) Definition Ratan_seq x := fun n => (x ^ (2 * n + 1) / INR (2 * n + 1))%R. -Lemma Ratan_seq_decreasing : forall x, (0 <= x <= 1)%R -> Un_decreasing (Ratan_seq x). +Lemma Ratan_seq_decreasing : forall x, (0 <= x <= 1)%R -> + Un_decreasing (Ratan_seq x). Proof. intros x Hx n. unfold Ratan_seq, Rdiv. @@ -780,7 +851,8 @@ intros x Hx n. lia. Qed. -Lemma Ratan_seq_converging : forall x, (0 <= x <= 1)%R -> Un_cv (Ratan_seq x) 0. +Lemma Ratan_seq_converging : forall x, (0 <= x <= 1)%R -> + Un_cv (Ratan_seq x) 0. Proof. intros x Hx eps Heps. destruct (archimed (/ eps)) as (HN,_). @@ -858,18 +930,18 @@ exact (alternated_series (Ratan_seq x) (Ratan_seq_decreasing _ Hx) (Ratan_seq_converging _ Hx)). Defined. -Lemma Ratan_seq_opp : forall x n, Ratan_seq (-x) n = -Ratan_seq x n. +Lemma Ratan_seq_opp : forall x n, + Ratan_seq (-x) n = -Ratan_seq x n. Proof. intros x n; unfold Ratan_seq. rewrite !pow_add, !pow_mult, !pow_1. unfold Rdiv; replace ((-x) ^ 2) with (x ^ 2) by ring; ring. Qed. -Lemma sum_Ratan_seq_opp : - forall x n, sum_f_R0 (tg_alt (Ratan_seq (- x))) n = - - sum_f_R0 (tg_alt (Ratan_seq x)) n. +Lemma sum_Ratan_seq_opp : forall x n, + sum_f_R0 (tg_alt (Ratan_seq (- x))) n = - sum_f_R0 (tg_alt (Ratan_seq x)) n. Proof. -intros x n; replace (-sum_f_R0 (tg_alt (Ratan_seq x)) n) with +intros x n; replace (-sum_f_R0 (tg_alt (Ratan_seq x)) n) with (-1 * sum_f_R0 (tg_alt (Ratan_seq x)) n) by ring. rewrite scal_sum; apply sum_eq; intros i _; unfold tg_alt. rewrite Ratan_seq_opp; ring. @@ -906,7 +978,7 @@ Definition ps_atan (x : R) : R := | right h => atan x end. -(** * Proof of the equivalence of the two definitions between -1 and 1 *) +(** ** Proof of the equivalence of the two definitions between -1 and 1 *) Lemma ps_atan0_0 : ps_atan 0 = 0. Proof. @@ -923,15 +995,14 @@ unfold ps_atan. case h2; split; lra. Qed. -Lemma ps_atan_exists_1_opp : - forall x h h', proj1_sig (ps_atan_exists_1 (-x) h) = - -(proj1_sig (ps_atan_exists_1 x h')). +Lemma ps_atan_exists_1_opp : forall x h h', + proj1_sig (ps_atan_exists_1 (-x) h) = -(proj1_sig (ps_atan_exists_1 x h')). Proof. intros x h h'; destruct (ps_atan_exists_1 (-x) h) as [v Pv]. destruct (ps_atan_exists_1 x h') as [u Pu]; simpl. assert (Pu' : Un_cv (fun N => (-1) * sum_f_R0 (tg_alt (Ratan_seq x)) N) (-1 * u)). apply CV_mult;[ | assumption]. - intros eps ep; exists 0%nat; intros; rewrite R_dist_eq; assumption. + intros eps ep; exists 0%nat; intros; rewrite R_dist_eq; assumption. assert (Pv' : Un_cv (fun N : nat => -1 * sum_f_R0 (tg_alt (Ratan_seq x)) N) v). apply Un_cv_ext with (2 := Pv); intros n; rewrite sum_Ratan_seq_opp; ring. @@ -939,7 +1010,8 @@ replace (-u) with (-1 * u) by ring. apply UL_sequence with (1:=Pv') (2:= Pu'). Qed. -Lemma ps_atan_opp : forall x, ps_atan (-x) = -ps_atan x. +Lemma ps_atan_opp : forall x, + ps_atan (-x) = -ps_atan x. Proof. intros x; unfold ps_atan. destruct (in_int (- x)) as [inside | outside]. @@ -954,10 +1026,9 @@ Qed. (** atan = ps_atan *) -Lemma ps_atanSeq_continuity_pt_1 : forall (N:nat) (x:R), - 0 <= x -> - x <= 1 -> - continuity_pt (fun x => sum_f_R0 (tg_alt (Ratan_seq x)) N) x. +Lemma ps_atanSeq_continuity_pt_1 : forall (N : nat) (x : R), + 0 <= x -> x <= 1 -> + continuity_pt (fun x => sum_f_R0 (tg_alt (Ratan_seq x)) N) x. Proof. assert (Sublemma : forall (x:R) (N:nat), sum_f_R0 (tg_alt (Ratan_seq x)) N = x * (comp (fun x => sum_f_R0 (fun n => (fun i : nat => (-1) ^ i / INR (2 * i + 1)) n * x ^ n) N) (fun x => x ^ 2) x)). intros x N. @@ -1020,10 +1091,11 @@ Qed. (** Definition of ps_atan's derivative *) -Definition Datan_seq := fun (x:R) (n:nat) => x ^ (2*n). +Definition Datan_seq := fun (x : R) (n : nat) => x ^ (2*n). -Lemma pow_lt_1_compat : forall x n, 0 <= x < 1 -> (0 < n)%nat -> - 0 <= x ^ n < 1. +Lemma pow_lt_1_compat : forall x n, + 0 <= x < 1 -> (0 < n)%nat -> + 0 <= x ^ n < 1. Proof. intros x n hx; induction 1; simpl. rewrite Rmult_1_r; tauto. @@ -1032,12 +1104,14 @@ split. rewrite <- (Rmult_1_r 1); apply Rmult_le_0_lt_compat; intuition. Qed. -Lemma Datan_seq_Rabs : forall x n, Datan_seq (Rabs x) n = Datan_seq x n. +Lemma Datan_seq_Rabs : forall x n, + Datan_seq (Rabs x) n = Datan_seq x n. Proof. intros x n; unfold Datan_seq; rewrite !pow_mult, pow2_abs; reflexivity. Qed. -Lemma Datan_seq_pos : forall x n, 0 < x -> 0 < Datan_seq x n. +Lemma Datan_seq_pos : forall x n, 0 < x -> + 0 < Datan_seq x n. Proof. intros x n x_lb ; unfold Datan_seq ; induction n. simpl ; intuition. @@ -1063,7 +1137,9 @@ f_equal. ring. Qed. -Lemma Datan_seq_increasing : forall x y n, (n > 0)%nat -> 0 <= x < y -> Datan_seq x n < Datan_seq y n. +Lemma Datan_seq_increasing : forall x y n, + (n > 0)%nat -> 0 <= x < y -> + Datan_seq x n < Datan_seq y n. Proof. intros x y n n_lb x_encad ; assert (x_pos : x >= 0) by intuition. assert (y_pos : y > 0). apply Rle_lt_trans with (r2:=x) ; intuition. @@ -1086,7 +1162,8 @@ intros x y n n_lb x_encad ; assert (x_pos : x >= 0) by intuition. rewrite pow_i. intuition. lia. Qed. -Lemma Datan_seq_decreasing : forall x, -1 < x -> x < 1 -> Un_decreasing (Datan_seq x). +Lemma Datan_seq_decreasing : forall x, -1 < x -> x < 1 -> + Un_decreasing (Datan_seq x). Proof. intros x x_lb x_ub n. unfold Datan_seq. @@ -1103,7 +1180,8 @@ apply (pow_lt_1_compat (Rabs x) 2) in intabs. lia. Qed. -Lemma Datan_seq_CV_0 : forall x, -1 < x -> x < 1 -> Un_cv (Datan_seq x) 0. +Lemma Datan_seq_CV_0 : forall x, -1 < x -> x < 1 -> + Un_cv (Datan_seq x) 0. Proof. intros x x_lb x_ub eps eps_pos. assert (x_ub2 : Rabs (x^2) < 1). @@ -1119,7 +1197,7 @@ rewrite pow_mult ; field. Qed. Lemma Datan_lim : forall x, -1 < x -> x < 1 -> - Un_cv (fun N : nat => sum_f_R0 (tg_alt (Datan_seq x)) N) (/ (1 + x ^ 2)). + Un_cv (fun N : nat => sum_f_R0 (tg_alt (Datan_seq x)) N) (/ (1 + x ^ 2)). Proof. intros x x_lb x_ub eps eps_pos. assert (Tool0 : 0 <= x ^ 2) by apply pow2_ge_0. @@ -1132,14 +1210,14 @@ assert (x_ub2' : 0<= Rabs (x^2) < 1). apply pow_lt_1_compat;[split;[apply Rabs_pos | ] | lia]. apply Rabs_def1; assumption. assert (x_ub2 : Rabs (x^2) < 1) by tauto. -assert (eps'_pos : ((1+x^2)*eps) > 0). +assert (eps'_pos : ((1 + x^2)*eps) > 0). apply Rmult_gt_0_compat ; assumption. elim (pow_lt_1_zero _ x_ub2 _ eps'_pos) ; intros N HN ; exists N. intros n Hn. assert (H1 : - x^2 <> 1). apply Rlt_not_eq; apply Rle_lt_trans with (2 := Rlt_0_1). assert (t := pow2_ge_0 x); lra. -rewrite Datan_sum_eq. +rewrite Datan_sum_eq. unfold R_dist. assert (tool : forall a b, a / b - /b = (-1 + a) /b). intros a b; rewrite <- (Rmult_1_l (/b)); unfold Rdiv, Rminus. @@ -1158,7 +1236,7 @@ assert (tool : forall k, Rabs ((-x ^ 2) ^ k) = Rabs ((x ^ 2) ^ k)). rewrite tool, (Rabs_pos_eq (/ _)); clear tool;[ | apply Rlt_le; assumption]. assert (tool : forall a b c, 0 < b -> a < b * c -> a * / b < c). intros a b c bp h; replace c with (b * c * /b). - apply Rmult_lt_compat_r. + apply Rmult_lt_compat_r. apply Rinv_0_lt_compat; assumption. assumption. field; apply Rgt_not_eq; exact bp. @@ -1167,11 +1245,11 @@ apply HN; lia. Qed. Lemma Datan_CVU_prelim : forall c (r : posreal), Rabs c + r < 1 -> - CVU (fun N x => sum_f_R0 (tg_alt (Datan_seq x)) N) - (fun y : R => / (1 + y ^ 2)) c r. + CVU (fun N x => sum_f_R0 (tg_alt (Datan_seq x)) N) + (fun y : R => / (1 + y ^ 2)) c r. Proof. intros c r ub_ub eps eps_pos. -apply (Alt_CVU (fun x n => Datan_seq n x) +apply (Alt_CVU (fun x n => Datan_seq n x) (fun x => /(1 + x ^ 2)) (Datan_seq (Rabs c + r)) c r). intros x inb; apply Datan_seq_decreasing; @@ -1198,10 +1276,9 @@ apply (Alt_CVU (fun x n => Datan_seq n x) assumption. Qed. -Lemma Datan_is_datan : forall (N:nat) (x:R), - -1 <= x -> - x < 1 -> -derivable_pt_lim (fun x => sum_f_R0 (tg_alt (Ratan_seq x)) N) x (sum_f_R0 (tg_alt (Datan_seq x)) N). +Lemma Datan_is_datan : forall (N : nat) (x : R), + -1 <= x -> x < 1 -> + derivable_pt_lim (fun x => sum_f_R0 (tg_alt (Ratan_seq x)) N) x (sum_f_R0 (tg_alt (Datan_seq x)) N). Proof. assert (Tool : forall N, (-1) ^ (S (2 * N)) = - 1). intro n ; induction n. @@ -1218,20 +1295,20 @@ intros N x x_lb x_ub. intros eps eps_pos. elim (derivable_pt_lim_id x eps eps_pos) ; intros delta Hdelta ; exists delta. intros h hneq h_b. - replace (1 * ((x + h) * 1 / 1) - 1 * (x * 1 / 1)) with (id (x + h) - id x). + replace (1 * ((x + h) * 1 / 1) - 1 * (x * 1 / 1)) with (id (x + h) - id x). rewrite Rmult_1_r. apply Hdelta ; assumption. unfold id ; field ; assumption. intros eps eps_pos. assert (eps_3_pos : (eps/3) > 0) by lra. elim (IHN (eps/3) eps_3_pos) ; intros delta1 Hdelta1. - assert (Main : derivable_pt_lim (fun x : R =>tg_alt (Ratan_seq x) (S N)) x ((tg_alt (Datan_seq x)) (S N))). + assert (Main : derivable_pt_lim (fun x =>tg_alt (Ratan_seq x) (S N)) x ((tg_alt (Datan_seq x)) (S N))). clear -Tool ; intros eps' eps'_pos. elim (derivable_pt_lim_pow x (2 * (S N) + 1) eps' eps'_pos) ; intros delta Hdelta ; exists delta. intros h h_neq h_b ; unfold tg_alt, Ratan_seq, Datan_seq. replace (((-1) ^ S N * ((x + h) ^ (2 * S N + 1) / INR (2 * S N + 1)) - (-1) ^ S N * (x ^ (2 * S N + 1) / INR (2 * S N + 1))) / h - - (-1) ^ S N * x ^ (2 * S N)) + (-1) ^ S N * x ^ (2 * S N)) with (((-1)^(S N)) * ((((x + h) ^ (2 * S N + 1) / INR (2 * S N + 1)) - (x ^ (2 * S N + 1) / INR (2 * S N + 1))) / h - x ^ (2 * S N))). rewrite Rabs_mult ; rewrite pow_1_abs ; rewrite Rmult_1_l. @@ -1299,9 +1376,9 @@ Qed. Lemma Ratan_CVU' : CVU (fun N x => sum_f_R0 (tg_alt (Ratan_seq x)) N) - ps_atan (/2) (mkposreal (/2) pos_half_prf). + ps_atan (/2) posreal_half. Proof. -apply (Alt_CVU (fun i r => Ratan_seq r i) ps_atan PI_tg (/2) pos_half); +apply (Alt_CVU (fun i r => Ratan_seq r i) ps_atan PI_tg (/2) posreal_half); lazy beta. now intros; apply Ratan_seq_decreasing, Boule_half_to_interval. now intros; apply Ratan_seq_converging, Boule_half_to_interval. @@ -1311,7 +1388,7 @@ apply (Alt_CVU (fun i r => Ratan_seq r i) ps_atan PI_tg (/2) pos_half); destruct (ps_atan_exists_1 x inside) as [v Pv]. apply Un_cv_ext with (2 := Pv);[reflexivity]. intros x n b; apply Boule_half_to_interval in b. - rewrite <- (Rmult_1_l (PI_tg n)); unfold Ratan_seq, PI_tg. + rewrite <- (Rmult_1_l (PI_tg n)); unfold Ratan_seq, PI_tg. apply Rmult_le_compat_r. apply Rlt_le, Rinv_0_lt_compat, (lt_INR 0); lia. rewrite <- (pow1 (2 * n + 1)); apply pow_incr; assumption. @@ -1320,12 +1397,12 @@ Qed. Lemma Ratan_CVU : CVU (fun N x => sum_f_R0 (tg_alt (Ratan_seq x)) N) - ps_atan 0 (mkposreal 1 Rlt_0_1). + ps_atan 0 (mkposreal 1 Rlt_0_1). Proof. intros eps ep; destruct (Ratan_CVU' eps ep) as [N Pn]. exists N; intros n x nN b_y. case (Rtotal_order 0 x) as [xgt0 | [x0 | x0]]. - assert (Boule (/2) {| pos := / 2; cond_pos := pos_half_prf|} x). + assert (Boule (/2) posreal_half x). revert b_y; unfold Boule; simpl; intros b_y; apply Rabs_def2 in b_y. destruct b_y; unfold Boule; simpl; apply Rabs_def1; lra. apply Pn; assumption. @@ -1338,7 +1415,7 @@ case (Rtotal_order 0 x) as [xgt0 | [x0 | x0]]. replace (ps_atan x - sum_f_R0 (tg_alt (Ratan_seq x)) n) with (-(ps_atan (-x) - sum_f_R0 (tg_alt (Ratan_seq (-x))) n)). rewrite Rabs_Ropp. - assert (Boule (/2) {| pos := / 2; cond_pos := pos_half_prf|} (-x)). + assert (Boule (/2) posreal_half (-x)). revert b_y; unfold Boule; simpl; intros b_y; apply Rabs_def2 in b_y. destruct b_y; unfold Boule; simpl; apply Rabs_def1; lra. apply Pn; assumption. @@ -1353,8 +1430,8 @@ reflexivity. Qed. Lemma Ratan_is_ps_atan : forall eps, eps > 0 -> - exists N, forall n, (n >= N)%nat -> forall x, -1 < x -> x < 1 -> - Rabs (sum_f_R0 (tg_alt (Ratan_seq x)) n - ps_atan x) < eps. + exists N, forall n, (n >= N)%nat -> forall x, -1 < x -> x < 1 -> + Rabs (sum_f_R0 (tg_alt (Ratan_seq x)) n - ps_atan x) < eps. Proof. intros eps ep. destruct (Ratan_CVU _ ep) as [N1 PN1]. @@ -1363,7 +1440,7 @@ apply PN1; [assumption | ]. unfold Boule; simpl; rewrite Rminus_0_r; apply Rabs_def1; assumption. Qed. -Lemma Datan_continuity : continuity (fun x => /(1+x ^ 2)). +Lemma Datan_continuity : continuity (fun x => /(1 + x^2)). Proof. apply continuity_inv. apply continuity_plus. @@ -1383,7 +1460,7 @@ intros x x_encad. destruct (boule_in_interval (-1) 1 x x_encad) as [c [r [Pcr1 [P1 P2]]]]. change (/ (1 + x ^ 2)) with ((fun u => /(1 + u ^ 2)) x). assert (t := derivable_pt_lim_CVU). -apply derivable_pt_lim_CVU with +apply derivable_pt_lim_CVU with (fn := (fun N x => sum_f_R0 (tg_alt (Ratan_seq x)) N)) (fn' := (fun N x => sum_f_R0 (tg_alt (Datan_seq x)) N)) (c := c) (r := r). @@ -1408,19 +1485,17 @@ apply derivable_pt_lim_CVU with intros; apply Datan_continuity. Qed. -Lemma derivable_pt_ps_atan : - forall x, -1 < x < 1 -> derivable_pt ps_atan x. +Lemma derivable_pt_ps_atan : forall x, -1 < x < 1 -> + derivable_pt ps_atan x. Proof. intros x x_encad. -exists (/(1+x^2)) ; apply derivable_pt_lim_ps_atan; assumption. +exists (/(1 + x^2)) ; apply derivable_pt_lim_ps_atan; assumption. Qed. Lemma ps_atan_continuity_pt_1 : forall eps : R, - eps > 0 -> - exists alp : R, - alp > 0 /\ - (forall x, x < 1 -> 0 < x -> R_dist x 1 < alp -> - dist R_met (ps_atan x) (Alt_PI/4) < eps). + eps > 0 -> + exists alp : R, alp > 0 /\ (forall x, x < 1 -> 0 < x -> R_dist x 1 < alp -> + dist R_met (ps_atan x) (Alt_PI/4) < eps). Proof. intros eps eps_pos. assert (eps_3_pos : eps / 3 > 0) by lra. @@ -1468,8 +1543,8 @@ ring. Qed. Lemma Datan_eq_DatanSeq_interv : forall x, -1 < x < 1 -> - forall (Pratan:derivable_pt ps_atan x) (Prmymeta:derivable_pt atan x), - derive_pt ps_atan x Pratan = derive_pt atan x Prmymeta. + forall (Pratan:derivable_pt ps_atan x) (Prmymeta:derivable_pt atan x), + derive_pt ps_atan x Pratan = derive_pt atan x Prmymeta. Proof. assert (freq : 0 < tan 1) by apply (Rlt_trans _ _ _ Rlt_0_1 tan_1_gt_1). intros x x_encad Pratan Prmymeta. @@ -1477,7 +1552,7 @@ intros x x_encad Pratan Prmymeta. (pr2 := derivable_pt_ps_atan x x_encad). rewrite pr_nu_var2_interv with (f:=atan) (g:=atan) (lb:=-1) (ub:= 1) (pr2:=derivable_pt_atan x). assert (Temp := derivable_pt_lim_ps_atan x x_encad). - assert (Hrew1 : derive_pt ps_atan x (derivable_pt_ps_atan x x_encad) = (/(1+x^2))). + assert (Hrew1 : derive_pt ps_atan x (derivable_pt_ps_atan x x_encad) = (/(1 + x^2))). apply derive_pt_eq_0 ; assumption. rewrite derive_pt_atan. rewrite Hrew1. @@ -1491,8 +1566,8 @@ intros x x_encad Pratan Prmymeta. intros; reflexivity. Qed. -Lemma atan_eq_ps_atan : - forall x, 0 < x < 1 -> atan x = ps_atan x. +Lemma atan_eq_ps_atan : forall x, 0 < x < 1 -> + atan x = ps_atan x. Proof. intros x x_encad. assert (pr1 : forall c : R, 0 < c < x -> derivable_pt (atan - ps_atan) c). @@ -1506,7 +1581,7 @@ assert (pr2 : forall c : R, 0 < c < x -> derivable_pt id c). assert (delta_cont : forall c : R, 0 <= c <= x -> continuity_pt (atan - ps_atan) c). intros c [[c_encad1 | c_encad1 ] [c_encad2 | c_encad2]]; apply continuity_pt_minus. - apply derivable_continuous_pt ; apply derivable_pt_atan. + apply derivable_continuous_pt ; apply derivable_pt_atan. apply derivable_continuous_pt ; apply derivable_pt_ps_atan. split; destruct x_encad; lra. apply derivable_continuous_pt, derivable_pt_atan. @@ -1532,20 +1607,20 @@ assert (Temp : forall (pr: derivable_pt (atan - ps_atan) d), derive_pt (atan - p unfold pr3. rewrite derive_pt_minus. rewrite Datan_eq_DatanSeq_interv with (Prmymeta := derivable_pt_atan d). intuition. - assumption. + assumption. destruct d_encad; lra. assumption. reflexivity. assert (iatan0 : atan 0 = 0). - apply tan_is_inj. + apply tan_inj. apply atan_bound. rewrite Ropp_div; assert (t := PI2_RGT_0); split; lra. - rewrite tan_0, atan_right_inv; reflexivity. + rewrite tan_0, tan_atan; reflexivity. generalize Main; rewrite Temp, Rmult_0_r. replace ((atan - ps_atan)%F x) with (atan x - ps_atan x) by intuition. replace ((atan - ps_atan)%F 0) with (atan 0 - ps_atan 0) by intuition. rewrite iatan0, ps_atan0_0, !Rminus_0_r. -replace (derive_pt id d (pr2 d d_encad)) with 1. +replace (derive_pt id d (pr2 d d_encad)) with 1. rewrite Rmult_1_r. solve[intros M; apply Rminus_diag_uniq; auto]. rewrite pr_nu_var with (g:=id) (pr2:=derivable_pt_id d). @@ -1553,7 +1628,6 @@ rewrite pr_nu_var with (g:=id) (pr2:=derivable_pt_id d). tauto. Qed. - Theorem Alt_PI_eq : Alt_PI = PI. Proof. apply Rmult_eq_reg_r with (/4); fold (Alt_PI/4); fold (PI/4); @@ -1585,7 +1659,7 @@ assert (Xa : exists a, 0 < a < 1 /\ R_dist a 1 < alpha /\ by (apply Rmax_lub_lt; lra). split;[split;[ | apply Rmax_lub_lt]; lra | ]. assert (0 <= 1 - Rmax (/ 2) (Rmax (1 - alpha / 2) (1 - beta / 2))). - assert (Rmax (/2) (Rmax (1 - alpha / 2) + assert (Rmax (/2) (Rmax (1 - alpha / 2) (1 - beta /2)) <= 1) by (apply Rmax_lub; lra). lra. split; unfold R_dist; rewrite <-Rabs_Ropp, Ropp_minus_distr, @@ -1602,10 +1676,504 @@ split;[exact I | apply Rgt_not_eq; assumption]. split; assumption. Qed. -Lemma PI_ineq : - forall N : nat, - sum_f_R0 (tg_alt PI_tg) (S (2 * N)) <= PI / 4 <= - sum_f_R0 (tg_alt PI_tg) (2 * N). +Lemma PI_ineq : forall N : nat, + sum_f_R0 (tg_alt PI_tg) (S (2 * N)) <= PI/4 <= sum_f_R0 (tg_alt PI_tg) (2 * N). Proof. intros; rewrite <- Alt_PI_eq; apply Alt_PI_ineq. Qed. + +(** ** Relation between arctangent and sine and cosine *) + +Lemma sin_atan: forall x, + sin (atan x) = x / sqrt (1 + x²). +Proof. +intros x. +pose proof (atan_right_inv x) as Hatan. +remember (atan(x)) as α. +rewrite <- Hatan. +apply sin_tan. +apply cos_gt_0. + all: pose proof atan_bound x; lra. +Qed. + +Lemma cos_atan: forall x, + cos (atan x) = 1 / sqrt(1 + x²). +Proof. + intros x. + pose proof (atan_right_inv x) as Hatan. + remember (atan(x)) as α. + rewrite <- Hatan. + apply cos_tan. + apply cos_gt_0. + all: pose proof atan_bound x; lra. +Qed. + +(*********************************************************) +(** * Definition of arcsine based on arctangent *) +(*********************************************************) + +(** asin is defined by cases so that it is defined in the full range from -1 .. 1 *) + +Definition asin x := + if Rle_dec x (-1) then - (PI / 2) else + if Rle_dec 1 x then PI / 2 else + atan (x / sqrt (1 - x²)). + +(** ** Relation between arcsin and arctangent *) + +Lemma asin_atan : forall x, -1 < x < 1 -> + asin x = atan (x / sqrt (1 - x²)). +Proof. +intros x. +unfold asin; repeat case Rle_dec; intros; lra. +Qed. + +(** ** arcsine of specific values *) + +Lemma asin_0 : asin 0 = 0. +Proof. +unfold asin; repeat case Rle_dec; intros; try lra. +replace (0/_) with 0. +- apply atan_0. +- field. + rewrite Rsqr_pow2; field_simplify (1 - 0^2). + rewrite sqrt_1; lra. +Qed. + +Lemma asin_1 : asin 1 = PI / 2. +Proof. +unfold asin; repeat case Rle_dec; lra. +Qed. + +Lemma asin_inv_sqrt2 : asin (/sqrt 2) = PI/4. +Proof. +rewrite asin_atan. + pose proof sqrt2_neq_0 as SH. + rewrite Rsqr_pow2, <-Rinv_pow, <- Rsqr_pow2, Rsqr_sqrt; try lra. + replace (1 - /2) with (/2) by lra. + rewrite <- inv_sqrt; try lra. + now rewrite <- atan_1; apply f_equal; field. +split. + apply (Rlt_trans _ 0); try lra. + now apply Rinv_0_lt_compat; apply sqrt_lt_R0; lra. +replace 1 with (/ sqrt 1). + apply Rinv_1_lt_contravar. + now rewrite sqrt_1; lra. + now apply sqrt_lt_1; lra. +now rewrite sqrt_1; lra. +Qed. + +Lemma asin_opp : forall x, + asin (- x) = - asin x. +Proof. +intros x. +unfold asin; repeat case Rle_dec; intros; try lra. +rewrite <- Rsqr_neg. +rewrite Ropp_div. +rewrite atan_opp. +reflexivity. +Qed. + +(** ** Bounds of arcsine *) + +Lemma asin_bound : forall x, + - (PI/2) <= asin x <= PI/2. +Proof. +intros x. +pose proof PI_RGT_0. +unfold asin; repeat case Rle_dec; try lra. +intros Hx1 Hx2. +pose proof atan_bound (x / sqrt (1 - x²)); lra. +Qed. + +Lemma asin_bound_lt : forall x, -1 < x < 1 -> + - (PI/2) < asin x < PI/2. +Proof. +intros x HxB. +pose proof PI_RGT_0. +unfold asin; repeat case Rle_dec; try lra. +intros Hx1 Hx2. +pose proof atan_bound (x / sqrt (1 - x²)); lra. +Qed. + +(** ** arcsine is the left and right inverse of sine *) + +Lemma sin_asin : forall x, -1 <= x <= 1 -> + sin (asin x) = x. +Proof. + intros x. +unfold asin; repeat case Rle_dec. + rewrite sin_antisym, sin_PI2; lra. + rewrite sin_PI2; lra. +intros Hx1 Hx2 Hx3. +rewrite sin_atan. +assert (forall a b c:R, b<>0 -> c<> 0 -> a/b/c = a/(b*c)) as R_divdiv_divmul by (intros; field; lra). +rewrite R_divdiv_divmul. + rewrite <- sqrt_mult_alt. + rewrite Rsqr_div, Rsqr_sqrt. + field_simplify((1 - x²) * (1 + x² / (1 - x²))). + rewrite sqrt_1. + field. +(* Pose a few things useful for several subgoals *) +all: pose proof Rsqr_bounds_lt 1 x ltac:(lra) as Hxsqr; + rewrite Rsqr_1 in Hxsqr. +all: pose proof sqrt_lt_R0 (1 - x²) ltac:(lra). +(* Do 6 first, because it produces more subgoals *) +all: swap 1 6. +rewrite Rsqr_div, Rsqr_sqrt. +field_simplify(1 + x² / (1 - x²)). +rewrite sqrt_div. +rewrite sqrt_1. +pose proof Rdiv_lt_0_compat 1 (sqrt (- x² + 1)) ltac:(lra) as Hrange. +pose proof sqrt_lt_R0 (- x² + 1) ltac:(lra) as Hrangep. +specialize (Hrange Hrangep). +lra. +(* The rest can all be done with lra *) +all: try lra. +Qed. + +Lemma asin_sin : forall x, -(PI/2) <= x <= PI/2 -> + asin (sin x) = x. +Proof. +intros x HB. +apply sin_inj; auto. + apply asin_bound. +apply sin_asin. +apply SIN_bound. +Qed. + +(** ** Relation between arcsin, cosine and tangent *) + +Lemma cos_asin : forall x, -1 <= x <= 1 -> + cos (asin x) = sqrt (1 - x²). +Proof. + intros x Hxrange. + pose proof (sin_asin x) ltac:(lra) as Hasin. + remember (asin(x)) as α. + rewrite <- Hasin. + apply cos_sin. + pose proof cos_ge_0 α. + pose proof asin_bound x. + lra. +Qed. + +Lemma tan_asin : forall x, -1 <= x <= 1 -> + tan (asin x) = x / sqrt (1 - x²). +Proof. + intros x Hxrange. + pose proof (sin_asin x) Hxrange as Hasin. + remember (asin(x)) as α. + rewrite <- Hasin. + apply tan_sin. + pose proof cos_ge_0 α. + pose proof asin_bound x. + lra. +Qed. + +(** ** Derivative of arcsine *) + +Lemma derivable_pt_asin : forall x, -1 < x < 1 -> + derivable_pt asin x. +Proof. + intros x H. + + eapply (derivable_pt_recip_interv sin asin (-PI/2) (PI/2)); [shelve ..|]. + + rewrite <- (pr_nu sin (asin x) (derivable_pt_sin (asin x))). + rewrite derive_pt_sin. + (* The asin bounds are needed later, so pose them before asin is unfolded *) + pose proof asin_bound_lt x ltac:(lra) as HxB3. + unfold asin in *. + destruct (Rle_dec x (-1)); destruct (Rle_dec 1 x); [lra .. |]. + apply Rgt_not_eq; apply cos_gt_0; lra. + + Unshelve. + - pose proof PI_RGT_0 as HPi; lra. + - rewrite Ropp_div,sin_antisym,sin_PI2; lra. + - clear x H; intros x Ha Hb. + rewrite Ropp_div; apply asin_bound. + - intros a Ha; reg. + - intros x0 Ha Hb. + unfold comp,id. + apply sin_asin. + rewrite Ropp_div,sin_antisym,sin_PI2 in Ha; rewrite sin_PI2 in Hb; lra. + - intros x1 x2 Ha Hb Hc. + apply sin_increasing_1; lra. +Qed. + +Lemma derive_pt_asin : forall (x : R) (Hxrange : -1 < x < 1), + derive_pt asin x (derivable_pt_asin x Hxrange) = 1 / sqrt (1 - x²). +Proof. + intros x Hxrange. + + epose proof (derive_pt_recip_interv sin asin (-PI/2) (PI/2) x _ _ _ _ _ _ _) as Hd. + + rewrite <- (pr_nu sin (asin x) (derivable_pt_sin (asin x))) in Hd. + rewrite <- (pr_nu asin x (derivable_pt_asin x Hxrange)) in Hd. + rewrite derive_pt_sin in Hd. + rewrite cos_asin in Hd by lra. + assumption. + + Unshelve. + - pose proof PI_RGT_0. lra. + - rewrite Ropp_div,sin_antisym,sin_PI2; lra. + - intros x1 x2 Ha Hb Hc. + apply sin_increasing_1; lra. + - intros x0 Ha Hb. + pose proof asin_bound x0; lra. + - intros a Ha; reg. + - intros x0 Ha Hb. + unfold comp,id. + apply sin_asin. + rewrite Ropp_div,sin_antisym,sin_PI2 in Ha; rewrite sin_PI2 in Hb; lra. + - rewrite <- (pr_nu sin (asin x) (derivable_pt_sin (asin x))). + rewrite derive_pt_sin. + rewrite cos_asin by lra. + apply Rgt_not_eq. + apply sqrt_lt_R0. + pose proof Rsqr_bounds_lt 1 x ltac:(lra) as Hxsqrrange. + rewrite Rsqr_1 in Hxsqrrange; lra. +Qed. + +(*********************************************************) +(** * Definition of arccosine based on arctangent *) +(*********************************************************) + +(** acos is defined by cases so that it is defined in the full range from -1 .. 1 *) + +Definition acos x := + if Rle_dec x (-1) then PI else + if Rle_dec 1 x then 0 else + PI/2 - atan (x/sqrt(1 - x²)). + +(** ** Relation between arccosine, arcsine and arctangent *) + +Lemma acos_atan : forall x, 0 < x -> + acos x = atan (sqrt (1 - x²) / x). +Proof. + intros x. + unfold acos; repeat case Rle_dec; [lra | |]. + - intros Hx1 Hx2 Hx3. + pose proof Rsqr_bounds_le x 1 ltac:(lra)as Hxsqr. + rewrite Rsqr_1 in Hxsqr. + rewrite sqrt_neg_0 by lra. + replace (0/x) with 0 by (field;lra). + rewrite atan_0; reflexivity. + - intros Hx1 Hx2 Hx3. + pose proof atan_inv (sqrt (1 - x²) / x) as Hatan. + pose proof Rsqr_bounds_lt 1 x ltac:(lra)as Hxsqr. + rewrite Rsqr_1 in Hxsqr. + replace (/ (sqrt (1 - x²) / x)) with (x/sqrt (1 - x²)) in Hatan. + + rewrite Hatan; [field|]. + apply Rdiv_lt_0_compat; [|assumption]. + apply sqrt_lt_R0; lra. + + field; split. + lra. + assert(sqrt (1 - x²) >0) by (apply sqrt_lt_R0; lra); lra. +Qed. + +Lemma acos_asin : forall x, -1 <= x <= 1 -> + acos x = PI/2 - asin x. +Proof. + intros x. + unfold acos, asin; repeat case Rle_dec; lra. +Qed. + +Lemma asin_acos : forall x, -1 <= x <= 1 -> + asin x = PI/2 - acos x. +Proof. + intros x. + unfold acos, asin; repeat case Rle_dec; lra. +Qed. + +(** ** arccosine of specific values *) + +Lemma acos_0 : acos 0 = PI/2. +Proof. + unfold acos; repeat case Rle_dec; [lra..|]. + intros Hx1 Hx2. + replace (0/_) with 0. + rewrite atan_0; field. + field. + rewrite Rsqr_pow2; field_simplify (1 - 0^2). + rewrite sqrt_1; lra. +Qed. + +Lemma acos_1 : acos 1 = 0. +Proof. + unfold acos; repeat case Rle_dec; lra. +Qed. + +Lemma acos_opp : forall x, + acos (- x) = PI - acos x. +Proof. + intros x. + unfold acos; repeat case Rle_dec; try lra. + intros Hx1 Hx2 Hx3 Hx4. + rewrite <- Rsqr_neg, Ropp_div, atan_opp. + lra. +Qed. + +Lemma acos_inv_sqrt2 : acos (/sqrt 2) = PI/4. +Proof. + rewrite acos_asin. + rewrite asin_inv_sqrt2. + lra. + split. + apply Rlt_le. + apply (Rlt_trans (-1) 0 (/ sqrt 2)); try lra. + apply Rinv_0_lt_compat. + apply Rlt_sqrt2_0. + replace 1 with (/ sqrt 1). + apply Rlt_le. + apply Rinv_1_lt_contravar. + rewrite sqrt_1; lra. + apply sqrt_lt_1; lra. + rewrite sqrt_1; lra. +Qed. + +(** ** Bounds of arccosine *) + +Lemma acos_bound : forall x, + 0 <= acos x <= PI. +Proof. + intros x. + pose proof PI_RGT_0. + unfold acos; repeat case Rle_dec; try lra. + intros Hx1 Hx2. + pose proof atan_bound (x / sqrt (1 - x²)); lra. +Qed. + +Lemma acos_bound_lt : forall x, -1 < x < 1 -> + 0 < acos x < PI. +Proof. + intros x xB. + pose proof PI_RGT_0. + unfold acos; repeat case Rle_dec; try lra. + intros Hx1 Hx2. + pose proof atan_bound (x / sqrt (1 - x²)); lra. +Qed. + +(** ** arccosine is the left and right inverse of cosine *) + +Lemma cos_acos : forall x, -1 <= x <= 1 -> + cos (acos x) = x. +Proof. + intros x xB. + assert (H : x = -1 \/ -1 < x) by lra. + destruct H as [He|Hl]. + rewrite He. + change (IZR (-1)) with (-(IZR 1)). + now rewrite acos_opp, acos_1, Rminus_0_r, cos_PI. + assert (H : x = 1 \/ x < 1) by lra. + destruct H as [He1|Hl1]. + now rewrite He1, acos_1, cos_0. + rewrite acos_asin, cos_shift; try lra. + rewrite sin_asin; lra. +Qed. + +Lemma acos_cos : forall x, 0 <= x <= PI -> + acos (cos x) = x. +Proof. + intros x HB. + apply cos_inj; try lra. + apply acos_bound. + apply cos_acos. + apply COS_bound. +Qed. + +(** ** Relation between arccosine, sine and tangent *) + +Lemma sin_acos : forall x, -1 <= x <= 1 -> + sin (acos x) = sqrt (1 - x²). +Proof. + intros x Hxrange. + pose proof (cos_acos x) ltac:(lra) as Hacos. + remember (acos(x)) as α. + rewrite <- Hacos. + apply sin_cos. + pose proof sin_ge_0 α. + pose proof acos_bound x. + lra. +Qed. + +Lemma tan_acos : forall x, -1 <= x <= 1 -> + tan (acos x) = sqrt (1 - x²) / x. +Proof. + intros x Hxrange. + pose proof (cos_acos x) Hxrange as Hacos. + remember (acos(x)) as α. + rewrite <- Hacos. + apply tan_cos. + pose proof sin_ge_0 α. + pose proof acos_bound x. + lra. +Qed. + +(** ** Derivative of arccosine *) + +Lemma derivable_pt_acos : forall x, -1 < x < 1 -> + derivable_pt acos x. +Proof. + intros x H. + + eapply (derivable_pt_recip_interv_decr cos acos 0 PI); [shelve ..|]. + + rewrite <- (pr_nu cos (acos x) (derivable_pt_cos (acos x))). + rewrite derive_pt_cos. + (* The acos bounds are needed later, so pose them before acos is unfolded *) + pose proof acos_bound_lt x ltac:(lra) as Hbnd. + unfold acos in *. + destruct (Rle_dec x (-1)); destruct (Rle_dec 1 x); [lra..|]. + apply Rlt_not_eq, Ropp_lt_gt_0_contravar, Rlt_gt. + apply sin_gt_0; lra. + + Unshelve. + - pose proof PI_RGT_0 as HPi; lra. + - rewrite cos_0; rewrite cos_PI; lra. + - clear x H; intros x H1 H2. + apply acos_bound. + - intros a Ha; reg. + - intros x0 H1 H2. + unfold comp,id. + apply cos_acos. + rewrite cos_PI in H1; rewrite cos_0 in H2; lra. + - intros x1 x2 H1 H2 H3. + pose proof cos_decreasing_1 x1 x2; lra. +Qed. + +Lemma derive_pt_acos : forall (x : R) (Hxrange : -1 < x < 1), + derive_pt acos x (derivable_pt_acos x Hxrange) = -1 / sqrt (1 - x²). +Proof. + intros x Hxrange. + + epose proof (derive_pt_recip_interv_decr cos acos 0 PI x _ _ _ _ _ _ _ ) as Hd. + + rewrite <- (pr_nu cos (acos x) (derivable_pt_cos (acos x))) in Hd. + rewrite <- (pr_nu acos x (derivable_pt_acos x Hxrange)) in Hd. + rewrite derive_pt_cos in Hd. + rewrite sin_acos in Hd by lra. + rewrite Hd; field. + apply Rgt_not_eq, Rlt_gt; rewrite <- sqrt_0. + pose proof Rsqr_bounds_lt 1 x ltac:(lra) as Hxb; rewrite Rsqr_1 in Hxb. + apply sqrt_lt_1; lra. + +Unshelve. + - pose proof PI_RGT_0; lra. + - rewrite cos_PI,cos_0; lra. + - intros x1 x2 Ha Hb Hc. + apply cos_decreasing_1; lra. + - intros x0 Ha Hb. + pose proof acos_bound x0; lra. + - intros a Ha; reg. + - intros x0 Ha Hb. + unfold comp,id. + apply cos_acos. + rewrite cos_PI in Ha; rewrite cos_0 in Hb; lra. + - rewrite <- (pr_nu cos (acos x) (derivable_pt_cos (acos x))). + rewrite derive_pt_cos. + rewrite sin_acos by lra. + apply Rlt_not_eq; rewrite <- Ropp_0; apply Ropp_lt_contravar; rewrite <- sqrt_0. + pose proof Rsqr_bounds_lt 1 x ltac:(lra) as Hxb; rewrite Rsqr_1 in Hxb. + apply sqrt_lt_1; lra. +Qed. diff --git a/theories/Reals/Raxioms.v b/theories/Reals/Raxioms.v index 57912a1196..8c5bc8475b 100644 --- a/theories/Reals/Raxioms.v +++ b/theories/Reals/Raxioms.v @@ -24,7 +24,7 @@ Require Import ClassicalDedekindReals. Require Import ConstructiveCauchyReals. Require Import ConstructiveCauchyRealsMult. Require Import ConstructiveRcomplete. -Require Import ConstructiveRealsLUB. +Require Import ConstructiveLUB. Require Export Rdefinitions. Local Open Scope R_scope. @@ -438,7 +438,7 @@ Proof. as Ebound. { destruct H. exists (Rrepr x). intros y Ey. rewrite <- (Rquot2 y). apply Rrepr_le. apply H. exact Ey. } - destruct (CR_sig_lub CRealImplem + destruct (@CR_sig_lub CRealConstructive Er Erproper sig_forall_dec sig_not_dec Einhab Ebound). exists (Rabst x). split. intros y Ey. apply Rrepr_le. rewrite Rquot2. diff --git a/theories/Reals/Rpower.v b/theories/Reals/Rpower.v index ad1b0e1ef7..047c9d0804 100644 --- a/theories/Reals/Rpower.v +++ b/theories/Reals/Rpower.v @@ -768,8 +768,6 @@ assert (t: forall x y z, x - z = y -> x - y - z = 0);[ | apply t; clear t]. intros a b c H; rewrite <- H; ring. apply Rmult_eq_reg_l with (2 * (x + sqrt (x ^ 2 + 1)));[ | apply Rgt_not_eq, Rmult_lt_0_compat;[apply Rlt_0_2 | assumption]]. -assert (pow2_sqrt : forall x, 0 <= x -> sqrt x ^ 2 = x) by - (intros; simpl; rewrite Rmult_1_r, sqrt_sqrt; auto). field_simplify;[rewrite pow2_sqrt;[field | ] | apply Rgt_not_eq; lra]. apply Rplus_le_le_0_compat;[simpl; rewrite Rmult_1_r; apply (Rle_0_sqr x)|apply Rlt_le, Rlt_0_1]. Qed. diff --git a/theories/Reals/Rtrigo1.v b/theories/Reals/Rtrigo1.v index d8c9c4f7ea..f5daa50ba4 100644 --- a/theories/Reals/Rtrigo1.v +++ b/theories/Reals/Rtrigo1.v @@ -1173,6 +1173,18 @@ Proof. apply (sin_increasing_1 (x - PI) (y - PI) H7 H8 H5 H6 H4). Qed. +Lemma sin_inj x y : -(PI/2) <= x <= PI/2 -> -(PI/2) <= y <= PI/2 -> sin x = sin y -> x = y. +Proof. +intros xP yP Hsin. +destruct (total_order_T x y) as [[H|H]|H]; auto. +- assert (sin x < sin y). + now apply sin_increasing_1; lra. + now lra. +- assert (sin y < sin x). + now apply sin_increasing_1; lra. + now lra. +Qed. + Lemma cos_increasing_0 : forall x y:R, PI <= x -> x <= 2 * PI -> PI <= y -> y <= 2 * PI -> cos x < cos y -> x < y. @@ -1253,6 +1265,18 @@ Proof. apply (cos_increasing_1 (PI + x) (PI + y) H3 H2 H1 H0 H). Qed. +Lemma cos_inj x y : 0 <= x <= PI -> 0 <= y <= PI -> cos x = cos y -> x = y. +Proof. +intros xP yP Hcos. +destruct (total_order_T x y) as [[H|H]|H]; auto. +- assert (cos y < cos x). + now apply cos_decreasing_1; lra. + now lra. +- assert (cos x < cos y). + now apply cos_decreasing_1; lra. + now lra. +Qed. + Lemma tan_diff : forall x y:R, cos x <> 0 -> cos y <> 0 -> tan x - tan y = sin (x - y) / (cos x * cos y). diff --git a/theories/Reals/Rtrigo_facts.v b/theories/Reals/Rtrigo_facts.v new file mode 100755 index 0000000000..9f2ad677a8 --- /dev/null +++ b/theories/Reals/Rtrigo_facts.v @@ -0,0 +1,287 @@ +(************************************************************************) +(* * The Coq Proof Assistant / The Coq Development Team *) +(* v * INRIA, CNRS and contributors - Copyright 1999-2019 *) +(* <O___,, * (see CREDITS file for the list of authors) *) +(* \VV/ **************************************************************) +(* // * This file is distributed under the terms of the *) +(* * GNU Lesser General Public License Version 2.1 *) +(* * (see LICENSE file for the text of the license) *) +(************************************************************************) + +Require Import Rbase. +Require Import Rtrigo1. +Require Import Rfunctions. + +Require Import Lra. +Require Import Ranalysis_reg. + +Local Open Scope R_scope. + +(*********************************************************) +(** * Bounds of expressions with trigonometric functions *) +(*********************************************************) + +Lemma sin2_bound : forall x, + 0 <= (sin x)² <= 1. +Proof. + intros x. + rewrite <- Rsqr_1. + apply Rsqr_bounds_le. + apply SIN_bound. +Qed. + +Lemma cos2_bound : forall x, + 0 <= (cos x)² <= 1. +Proof. + intros x. + rewrite <- Rsqr_1. + apply Rsqr_bounds_le. + apply COS_bound. +Qed. + +(*********************************************************) +(** * Express trigonometric functions with each other *) +(*********************************************************) + +(** ** Express sin and cos with each other *) + +Lemma cos_sin : forall x, cos x >=0 -> + cos x = sqrt(1 - (sin x)²). +Proof. + intros x H. + apply Rsqr_inj. + - lra. + - apply sqrt_pos. + - rewrite Rsqr_sqrt. + apply cos2. + pose proof sin2_bound x. + lra. +Qed. + +Lemma cos_sin_opp : forall x, cos x <=0 -> + cos x = - sqrt(1 - (sin x)²). +Proof. + intros x H. + rewrite <- (Ropp_involutive (cos x)). + apply Ropp_eq_compat. + apply Rsqr_inj. + - lra. + - apply sqrt_pos. + - rewrite Rsqr_sqrt. + rewrite <- Rsqr_neg. + apply cos2. + pose proof sin2_bound x. + lra. +Qed. + +Lemma cos_sin_Rabs : forall x, + Rabs (cos x) = sqrt(1 - (sin x)²). +Proof. + intros x. + unfold Rabs. + destruct (Rcase_abs (cos x)). + - rewrite <- (Ropp_involutive (sqrt (1 - (sin x)²))). + apply Ropp_eq_compat. + apply cos_sin_opp; lra. + - apply cos_sin; assumption. +Qed. + +Lemma sin_cos : forall x, sin x >=0 -> + sin x = sqrt(1 - (cos x)²). +Proof. + intros x H. + apply Rsqr_inj. + - lra. + - apply sqrt_pos. + - rewrite Rsqr_sqrt. + apply sin2. + pose proof cos2_bound x. + lra. +Qed. + +Lemma sin_cos_opp : forall x, sin x <=0 -> + sin x = - sqrt(1 - (cos x)²). +Proof. + intros x H. + rewrite <- (Ropp_involutive (sin x)). + apply Ropp_eq_compat. + apply Rsqr_inj. + - lra. + - apply sqrt_pos. + - rewrite Rsqr_sqrt. + rewrite <- Rsqr_neg. + apply sin2. + pose proof cos2_bound x. + lra. +Qed. + +Lemma sin_cos_Rabs : forall x, + Rabs (sin x) = sqrt(1 - (cos x)²). +Proof. + intros x. + unfold Rabs. + destruct (Rcase_abs (sin x)). + - rewrite <- ( Ropp_involutive (sqrt (1 - (cos x)²))). + apply Ropp_eq_compat. + apply sin_cos_opp; lra. + - apply sin_cos; assumption. +Qed. + +(** ** Express tan with sin and cos *) + +Lemma tan_sin : forall x, 0 <= cos x -> + tan x = sin x / sqrt (1 - (sin x)²). +Proof. + intros x H. + unfold tan. + rewrite <- (sqrt_Rsqr (cos x)) by assumption. + rewrite <- (cos2 x). + reflexivity. +Qed. + +Lemma tan_sin_opp : forall x, 0 > cos x -> + tan x = - (sin x / sqrt (1 - (sin x)²)). +Proof. + intros x H. + unfold tan. + rewrite cos_sin_opp by lra. + rewrite Ropp_div_den. + reflexivity. + pose proof cos_sin_opp x. + lra. +Qed. + +(** Note: tan_sin_Rabs wouldn't make a lot of sense, because one would need Rabs on both sides *) + +Lemma tan_cos : forall x, 0 <= sin x -> + tan x = sqrt (1 - (cos x)²) / cos x. +Proof. + intros x H. + unfold tan. + rewrite <- (sqrt_Rsqr (sin x)) by assumption. + rewrite <- (sin2 x). + reflexivity. +Qed. + +Lemma tan_cos_opp : forall x, 0 >= sin x -> + tan x = - sqrt (1 - (cos x)²) / cos x. +Proof. + intros x H. + unfold tan. + rewrite sin_cos_opp by lra. + reflexivity. +Qed. + +(** ** Express sin and cos with tan *) + +Lemma sin_tan : forall x, 0 < cos x -> + sin x = tan x / sqrt (1 + (tan x)²). +Proof. + intros. + assert(Hcosle:0<=cos x) by lra. + pose proof tan_sin x Hcosle as Htan. + rewrite Htan. + repeat rewrite <- Rsqr_pow2 in *. + assert (forall a b c:R, b<>0 -> c<> 0 -> a/b/c = a/(b*c)) as R_divdiv_divmul by (intros; field; lra). + rewrite R_divdiv_divmul. + rewrite <- sqrt_mult_alt. + rewrite Rsqr_div, Rsqr_sqrt. + field_simplify ((1 - (sin x)²) * (1 + (sin x)² / (1 - (sin x)²))). + rewrite sqrt_1. + field. + all: pose proof (sin2 x); pose proof Rsqr_pos_lt (cos x); try lra. + all: assert( forall a, 0 < a -> a <> 0) as Hne by (intros; lra). + all: apply Hne, sqrt_lt_R0; try lra. + rewrite <- Htan. + pose proof Rle_0_sqr (tan x); lra. +Qed. + +Lemma cos_tan : forall x, 0 < cos x -> + cos x = 1 / sqrt (1 + (tan x)²). +Proof. + intros. + destruct (Rcase_abs (sin x)) as [Hsignsin|Hsignsin]. + - assert(Hsinle:0>=sin x) by lra. + pose proof tan_cos_opp x Hsinle as Htan. + rewrite Htan. + rewrite Rsqr_div. + rewrite <- Rsqr_neg. + rewrite Rsqr_sqrt. + field_simplify( 1 + (1 - (cos x)²) / (cos x)² ). + rewrite sqrt_div_alt. + rewrite sqrt_1. + field_simplify_eq. + rewrite sqrt_Rsqr. + reflexivity. + all: pose proof cos2_bound x. + all: pose proof Rsqr_pos_lt (cos x) ltac:(lra). + all: pose proof sqrt_lt_R0 (cos x)² ltac:(assumption). + all: lra. + - assert(Hsinge:0<=sin x) by lra. + pose proof tan_cos x Hsinge as Htan. + rewrite Htan. + rewrite Rsqr_div. + rewrite Rsqr_sqrt. + field_simplify( 1 + (1 - (cos x)²) / (cos x)² ). + rewrite sqrt_div_alt. + rewrite sqrt_1. + field_simplify_eq. + rewrite sqrt_Rsqr. + reflexivity. + all: pose proof cos2_bound x. + all: pose proof Rsqr_pos_lt (cos x) ltac:(lra). + all: pose proof sqrt_lt_R0 (cos x)² ltac:(assumption). + all: lra. +Qed. + +(*********************************************************) +(** * Additional shift lemmas for sin, cos, tan *) +(*********************************************************) + +Lemma sin_pi_minus : forall x, + sin (PI - x) = sin x. +Proof. + intros x. + rewrite sin_minus, cos_PI, sin_PI. + ring. +Qed. + +Lemma sin_pi_plus : forall x, + sin (PI + x) = - sin x. +Proof. + intros x. + rewrite sin_plus, cos_PI, sin_PI. + ring. +Qed. + +Lemma cos_pi_minus : forall x, + cos (PI - x) = - cos x. +Proof. + intros x. + rewrite cos_minus, cos_PI, sin_PI. + ring. +Qed. + +Lemma cos_pi_plus : forall x, + cos (PI + x) = - cos x. +Proof. + intros x. + rewrite cos_plus, cos_PI, sin_PI. + ring. +Qed. + +Lemma tan_pi_minus : forall x, cos x <> 0 -> + tan (PI - x) = - tan x. +Proof. + intros x H. + unfold tan; rewrite sin_pi_minus, cos_pi_minus. + field; assumption. +Qed. + +Lemma tan_pi_plus : forall x, cos x <> 0 -> + tan (PI + x) = tan x. +Proof. + intros x H. + unfold tan; rewrite sin_pi_plus, cos_pi_plus. + field; assumption. +Qed. diff --git a/theories/Sorting/Mergesort.v b/theories/Sorting/Mergesort.v index a761dba62d..f6a1efdd37 100644 --- a/theories/Sorting/Mergesort.v +++ b/theories/Sorting/Mergesort.v @@ -230,13 +230,13 @@ Proof. apply IHl. Qed. -Theorem Sorted_sort : forall l, Sorted (sort l). +Theorem LocallySorted_sort : forall l, Sorted (sort l). Proof. intro; apply Sorted_iter_merge. constructor. Qed. -Corollary LocallySorted_sort : forall l, Sorted.Sorted leb (sort l). -Proof. intro; eapply Sorted_LocallySorted_iff, Sorted_sort; auto. Qed. +Corollary Sorted_sort : forall l, Sorted.Sorted leb (sort l). +Proof. intro; eapply Sorted_LocallySorted_iff, LocallySorted_sort; auto. Qed. Theorem Permuted_sort : forall l, Permutation l (sort l). Proof. @@ -245,7 +245,7 @@ Qed. Corollary StronglySorted_sort : forall l, Transitive leb -> StronglySorted leb (sort l). -Proof. auto using Sorted_StronglySorted, LocallySorted_sort. Qed. +Proof. auto using Sorted_StronglySorted, Sorted_sort. Qed. End Sort. @@ -259,7 +259,7 @@ Module NatOrder <: TotalLeBool. | _, 0 => false | S x', S y' => leb x' y' end. - Infix "<=?" := leb (at level 35). + Infix "<=?" := leb (at level 70, no associativity). Theorem leb_total : forall a1 a2, a1 <=? a2 \/ a2 <=? a1. Proof. induction a1; destruct a2; simpl; auto. @@ -269,4 +269,3 @@ End NatOrder. Module Import NatSort := Sort NatOrder. Example SimpleMergeExample := Eval compute in sort [5;3;6;1;8;6;0]. - diff --git a/theories/Sorting/Permutation.v b/theories/Sorting/Permutation.v index 23881f63cb..86eebc6b4f 100644 --- a/theories/Sorting/Permutation.v +++ b/theories/Sorting/Permutation.v @@ -15,7 +15,7 @@ (* Adapted in May 2006 by Jean-Marc Notin from initial contents by Laurent Théry (Huffmann contribution, October 2003) *) -Require Import List Setoid Compare_dec Morphisms FinFun. +Require Import List Setoid Compare_dec Morphisms FinFun PeanoNat. Import ListNotations. (* For notations [] and [a;b;c] *) Set Implicit Arguments. (* Set Universe Polymorphism. *) @@ -56,6 +56,11 @@ Proof. induction l; constructor. exact IHl. Qed. +Instance Permutation_refl' : Proper (Logic.eq ==> Permutation) id. +Proof. + intros x y Heq; rewrite Heq; apply Permutation_refl. +Qed. + Theorem Permutation_sym : forall l l' : list A, Permutation l l' -> Permutation l' l. Proof. @@ -87,15 +92,28 @@ Instance Permutation_Equivalence A : Equivalence (@Permutation A) | 10 := { Equivalence_Symmetric := @Permutation_sym A ; Equivalence_Transitive := @Permutation_trans A }. +Lemma Permutation_morph_transp A : forall P : list A -> Prop, + (forall a b l1 l2, P (l1 ++ a :: b :: l2) -> P (l1 ++ b :: a :: l2)) -> + Proper (@Permutation A ==> Basics.impl) P. +Proof. + intros P HT l1 l2 HP. + enough (forall l0, P (l0 ++ l1) -> P (l0 ++ l2)) as IH + by (intro; rewrite <- (app_nil_l l2); now apply (IH nil)). + induction HP; intuition. + rewrite <- (app_nil_l l'), app_comm_cons, app_assoc. + now apply IHHP; rewrite <- app_assoc. +Qed. + Instance Permutation_cons A : Proper (Logic.eq ==> @Permutation A ==> @Permutation A) (@cons A) | 10. Proof. repeat intro; subst; auto using perm_skip. Qed. + Section Permutation_properties. -Variable A:Type. +Variable A B:Type. Implicit Types a b : A. Implicit Types l m : list A. @@ -168,6 +186,30 @@ Proof. Qed. Local Hint Resolve Permutation_app_comm : core. +Lemma Permutation_app_rot : forall l1 l2 l3: list A, + Permutation (l1 ++ l2 ++ l3) (l2 ++ l3 ++ l1). +Proof. + intros l1 l2 l3; now rewrite (app_assoc l2). +Qed. +Local Hint Resolve Permutation_app_rot : core. + +Lemma Permutation_app_swap_app : forall l1 l2 l3: list A, + Permutation (l1 ++ l2 ++ l3) (l2 ++ l1 ++ l3). +Proof. + intros. + rewrite 2 app_assoc. + apply Permutation_app_tail, Permutation_app_comm. +Qed. +Local Hint Resolve Permutation_app_swap_app : core. + +Lemma Permutation_app_middle : forall l l1 l2 l3 l4, + Permutation (l1 ++ l2) (l3 ++ l4) -> + Permutation (l1 ++ l ++ l2) (l3 ++ l ++ l4). +Proof. + intros l l1 l2 l3 l4 HP. + now rewrite Permutation_app_swap_app, HP, Permutation_app_swap_app. +Qed. + Theorem Permutation_cons_app : forall (l l1 l2:list A) a, Permutation l (l1 ++ l2) -> Permutation (a :: l) (l1 ++ a :: l2). Proof. @@ -190,6 +232,24 @@ Proof. Qed. Local Hint Resolve Permutation_middle : core. +Lemma Permutation_middle2 : forall l1 l2 l3 a b, + Permutation (a :: b :: l1 ++ l2 ++ l3) (l1 ++ a :: l2 ++ b :: l3). +Proof. + intros l1 l2 l3 a b. + apply Permutation_cons_app. + rewrite 2 app_assoc. + now apply Permutation_cons_app. +Qed. +Local Hint Resolve Permutation_middle2 : core. + +Lemma Permutation_elt : forall l1 l2 l1' l2' (a:A), + Permutation (l1 ++ l2) (l1' ++ l2') -> + Permutation (l1 ++ a :: l2) (l1' ++ a :: l2'). +Proof. + intros l1 l2 l1' l2' a HP. + transitivity (a :: l1 ++ l2); auto. +Qed. + Theorem Permutation_rev : forall (l : list A), Permutation l (rev l). Proof. induction l as [| x l]; simpl; trivial. now rewrite IHl at 1. @@ -213,6 +273,46 @@ Proof. exact Permutation_length. Qed. +Instance Permutation_Forall (P : A -> Prop) : + Proper ((@Permutation A) ==> Basics.impl) (Forall P). +Proof. + intros l1 l2 HP. + induction HP; intro HF; auto. + - inversion_clear HF; auto. + - inversion_clear HF as [ | ? ? HF1 HF2]. + inversion_clear HF2; auto. +Qed. + +Instance Permutation_Exists (P : A -> Prop) : + Proper ((@Permutation A) ==> Basics.impl) (Exists P). +Proof. + intros l1 l2 HP. + induction HP; intro HF; auto. + - inversion_clear HF; auto. + - inversion_clear HF as [ | ? ? HF1 ]; auto. + inversion_clear HF1; auto. +Qed. + +Lemma Permutation_Forall2 (P : A -> B -> Prop) : + forall l1 l1' (l2 : list B), Permutation l1 l1' -> Forall2 P l1 l2 -> + exists l2' : list B, Permutation l2 l2' /\ Forall2 P l1' l2'. +Proof. + intros l1 l1' l2 HP. + revert l2; induction HP; intros l2 HF; inversion HF as [ | ? b ? ? HF1 HF2 ]; subst. + - now exists nil. + - apply IHHP in HF2 as [l2' [HP2 HF2]]. + exists (b :: l2'); auto. + - inversion_clear HF2 as [ | ? b' ? l2' HF3 HF4 ]. + exists (b' :: b :: l2'); auto. + - apply Permutation_nil in HP1; subst. + apply Permutation_nil in HP2; subst. + now exists nil. + - apply IHHP1 in HF as [l2' [HP2' HF2']]. + apply IHHP2 in HF2' as [l2'' [HP2'' HF2'']]. + exists l2''; split; auto. + now transitivity l2'. +Qed. + Theorem Permutation_ind_bis : forall P : list A -> list A -> Prop, P [] [] -> @@ -301,6 +401,16 @@ Proof. rewrite 2 (Permutation_app_comm _ l). apply Permutation_app_inv_l. Qed. +Lemma Permutation_app_inv_m l l1 l2 l3 l4 : + Permutation (l1 ++ l ++ l2) (l3 ++ l ++ l4) -> + Permutation (l1 ++ l2) (l3 ++ l4). +Proof. + intros HP. + apply (Permutation_app_inv_l l). + transitivity (l1 ++ l ++ l2); auto. + transitivity (l3 ++ l ++ l4); auto. +Qed. + Lemma Permutation_length_1_inv: forall a l, Permutation [a] l -> l = [a]. Proof. intros a l H; remember [a] as m in H. @@ -335,6 +445,38 @@ Proof. apply Permutation_length_2_inv in H as [H|H]; injection H as [= -> ->]; auto. Qed. +Lemma Permutation_vs_elt_inv : forall l l1 l2 a, + Permutation l (l1 ++ a :: l2) -> exists l' l'', l = l' ++ a :: l''. +Proof. + intros l l1 l2 a HP. + symmetry in HP. + apply (Permutation_in a), in_split in HP; trivial. + apply in_elt. +Qed. + +Lemma Permutation_vs_cons_inv : forall l l1 a, + Permutation l (a :: l1) -> exists l' l'', l = l' ++ a :: l''. +Proof. + intros l l1 a HP. + rewrite <- (app_nil_l (a :: l1)) in HP. + apply (Permutation_vs_elt_inv _ _ _ HP). +Qed. + +Lemma Permutation_vs_cons_cons_inv : forall l l' a b, + Permutation l (a :: b :: l') -> + exists l1 l2 l3, l = l1 ++ a :: l2 ++ b :: l3 \/ l = l1 ++ b :: l2 ++ a :: l3. +Proof. + intros l l' a b HP. + destruct (Permutation_vs_cons_inv HP) as [l1 [l2]]; subst. + symmetry in HP. + apply Permutation_cons_app_inv in HP. + apply (Permutation_in b), in_app_or in HP; [|now apply in_eq]. + destruct HP as [(l3 & l4 & ->)%in_split | (l3 & l4 & ->)%in_split]. + - exists l3, l4, l2; right. + now rewrite <-app_assoc; simpl. + - now exists l1, l3, l4; left. +Qed. + Lemma NoDup_Permutation l l' : NoDup l -> NoDup l' -> (forall x:A, In x l <-> In x l') -> Permutation l l'. Proof. @@ -367,8 +509,8 @@ Qed. Lemma Permutation_NoDup l l' : Permutation l l' -> NoDup l -> NoDup l'. Proof. induction 1; auto. - * inversion_clear 1; constructor; eauto using Permutation_in. - * inversion_clear 1 as [|? ? H1 H2]. inversion_clear H2; simpl in *. + - inversion_clear 1; constructor; eauto using Permutation_in. + - inversion_clear 1 as [|? ? H1 H2]. inversion_clear H2; simpl in *. constructor. simpl; intuition. constructor; intuition. Qed. @@ -397,6 +539,63 @@ Proof. exact Permutation_map. Qed. +Lemma Permutation_map_inv : forall l1 l2, + Permutation l1 (map f l2) -> exists l3, l1 = map f l3 /\ Permutation l2 l3. +Proof. + induction l1; intros l2 HP. + - exists nil; split; auto. + apply Permutation_nil in HP. + destruct l2; auto. + inversion HP. + - symmetry in HP. + destruct (Permutation_vs_cons_inv HP) as [l3 [l4 Heq]]. + destruct (map_eq_app _ _ _ _ Heq) as [l1' [l2' [Heq1 [Heq2 Heq3]]]]; subst. + symmetry in Heq3. + destruct (map_eq_cons _ _ Heq3) as [b [l1'' [Heq1' [Heq2' Heq3']]]]; subst. + rewrite map_app in HP; simpl in HP. + symmetry in HP. + apply Permutation_cons_app_inv in HP. + rewrite <- map_app in HP. + destruct (IHl1 _ HP) as [l3 [Heq1'' Heq2'']]; subst. + exists (b :: l3); split; auto. + symmetry in Heq2''; symmetry; apply (Permutation_cons_app _ _ _ Heq2''). +Qed. + +Lemma Permutation_image : forall a l l', + Permutation (a :: l) (map f l') -> exists a', a = f a'. +Proof. + intros a l l' HP. + destruct (Permutation_map_inv _ HP) as [l'' [Heq _]]. + destruct l'' as [ | a' l'']; inversion_clear Heq. + now exists a'. +Qed. + +Lemma Permutation_elt_map_inv: forall l1 l2 l3 l4 a, + Permutation (l1 ++ a :: l2) (l3 ++ map f l4) -> (forall b, a <> f b) -> + exists l1' l2', l3 = l1' ++ a :: l2'. +Proof. + intros l1 l2 l3 l4 a HP Hf. + apply (Permutation_in a), in_app_or in HP; [| now apply in_elt]. + destruct HP as [HP%in_split | (x & Heq & ?)%in_map_iff]; trivial; subst. + now contradiction (Hf x). +Qed. + +Instance Permutation_flat_map (g : A -> list B) : + Proper ((@Permutation A) ==> (@Permutation B)) (flat_map g). +Proof. + intros l1; induction l1; intros l2 HP. + - now apply Permutation_nil in HP; subst. + - symmetry in HP. + destruct (Permutation_vs_cons_inv HP) as [l' [l'']]; subst. + symmetry in HP. + apply Permutation_cons_app_inv in HP. + rewrite flat_map_app; simpl. + rewrite <- (app_nil_l _). + apply Permutation_app_middle; simpl. + rewrite <- flat_map_app. + apply (IHl1 _ HP). +Qed. + End Permutation_map. Lemma nat_bijection_Permutation n f : @@ -573,6 +772,86 @@ Qed. End Permutation_alt. +Instance Permutation_list_sum : Proper (@Permutation nat ==> eq) list_sum. +Proof. + intros l1 l2 HP; induction HP; simpl; intuition. + - rewrite 2 (Nat.add_comm x). + apply Nat.add_assoc. + - now transitivity (list_sum l'). +Qed. + +Instance Permutation_list_max : Proper (@Permutation nat ==> eq) list_max. +Proof. + intros l1 l2 HP; induction HP; simpl; intuition. + - rewrite 2 (Nat.max_comm x). + apply Nat.max_assoc. + - now transitivity (list_max l'). +Qed. + +Section Permutation_transp. + +Variable A:Type. + +(** Permutation definition based on transpositions for induction with fixed length *) +Inductive Permutation_transp : list A -> list A -> Prop := +| perm_t_refl : forall l, Permutation_transp l l +| perm_t_swap : forall x y l1 l2, Permutation_transp (l1 ++ y :: x :: l2) (l1 ++ x :: y :: l2) +| perm_t_trans l l' l'' : + Permutation_transp l l' -> Permutation_transp l' l'' -> Permutation_transp l l''. + +Instance Permutation_transp_sym : Symmetric Permutation_transp. +Proof. + intros l1 l2 HP; induction HP; subst; try (now constructor). + now apply (perm_t_trans IHHP2). +Qed. + +Instance Permutation_transp_equiv : Equivalence Permutation_transp. +Proof. + split. + - intros l; apply perm_t_refl. + - apply Permutation_transp_sym. + - intros l1 l2 l3 ;apply perm_t_trans. +Qed. + +Lemma Permutation_transp_cons : forall (x : A) l1 l2, + Permutation_transp l1 l2 -> Permutation_transp (x :: l1) (x :: l2). +Proof. + intros x l1 l2 HP. + induction HP. + - reflexivity. + - rewrite 2 app_comm_cons. + apply perm_t_swap. + - now transitivity (x :: l'). +Qed. + +Lemma Permutation_Permutation_transp : forall l1 l2 : list A, + Permutation l1 l2 <-> Permutation_transp l1 l2. +Proof. + intros l1 l2; split; intros HP; induction HP; intuition. + - now apply Permutation_transp_cons. + - rewrite <- (app_nil_l (y :: _)). + rewrite <- (app_nil_l (x :: y :: _)). + apply perm_t_swap. + - now transitivity l'. + - apply Permutation_app_head. + apply perm_swap. + - now transitivity l'. +Qed. + +Lemma Permutation_ind_transp : forall P : list A -> list A -> Prop, + (forall l, P l l) -> + (forall x y l1 l2, P (l1 ++ y :: x :: l2) (l1 ++ x :: y :: l2)) -> + (forall l l' l'', + Permutation l l' -> P l l' -> Permutation l' l'' -> P l' l'' -> P l l'') -> + forall l1 l2, Permutation l1 l2 -> P l1 l2. +Proof. + intros P Hr Ht Htr l1 l2 HP; apply Permutation_Permutation_transp in HP. + revert Hr Ht Htr; induction HP; intros Hr Ht Htr; auto. + apply (Htr _ l'); intuition; now apply Permutation_Permutation_transp. +Qed. + +End Permutation_transp. + (* begin hide *) Notation Permutation_app_swap := Permutation_app_comm (only parsing). (* end hide *) diff --git a/theories/Structures/Orders.v b/theories/Structures/Orders.v index 6a0e7397eb..94938c1d4d 100644 --- a/theories/Structures/Orders.v +++ b/theories/Structures/Orders.v @@ -192,11 +192,11 @@ Module Type HasLtb (Import T:Typ). End HasLtb. Module Type LebNotation (T:Typ)(E:HasLeb T). - Infix "<=?" := E.leb (at level 35). + Infix "<=?" := E.leb (at level 70, no associativity). End LebNotation. Module Type LtbNotation (T:Typ)(E:HasLtb T). - Infix "<?" := E.ltb (at level 35). + Infix "<?" := E.ltb (at level 70, no associativity). End LtbNotation. Module Type LebSpec (T:Typ)(X:HasLe T)(Y:HasLeb T). diff --git a/theories/omega/Omega.v b/theories/omega/Omega.v index 9c2e8a9212..10a5aa47b3 100644 --- a/theories/omega/Omega.v +++ b/theories/omega/Omega.v @@ -19,6 +19,7 @@ Require Export ZArith_base. Require Export OmegaLemmas. Require Export PreOmega. +Require Import Lia. Declare ML Module "omega_plugin". @@ -28,28 +29,28 @@ Hint Resolve Z.le_refl Z.add_comm Z.add_assoc Z.mul_comm Z.mul_assoc Z.add_0_l Require Export Zhints. -Hint Extern 10 (_ = _ :>nat) => abstract omega: zarith. -Hint Extern 10 (_ <= _) => abstract omega: zarith. -Hint Extern 10 (_ < _) => abstract omega: zarith. -Hint Extern 10 (_ >= _) => abstract omega: zarith. -Hint Extern 10 (_ > _) => abstract omega: zarith. - -Hint Extern 10 (_ <> _ :>nat) => abstract omega: zarith. -Hint Extern 10 (~ _ <= _) => abstract omega: zarith. -Hint Extern 10 (~ _ < _) => abstract omega: zarith. -Hint Extern 10 (~ _ >= _) => abstract omega: zarith. -Hint Extern 10 (~ _ > _) => abstract omega: zarith. - -Hint Extern 10 (_ = _ :>Z) => abstract omega: zarith. -Hint Extern 10 (_ <= _)%Z => abstract omega: zarith. -Hint Extern 10 (_ < _)%Z => abstract omega: zarith. -Hint Extern 10 (_ >= _)%Z => abstract omega: zarith. -Hint Extern 10 (_ > _)%Z => abstract omega: zarith. - -Hint Extern 10 (_ <> _ :>Z) => abstract omega: zarith. -Hint Extern 10 (~ (_ <= _)%Z) => abstract omega: zarith. -Hint Extern 10 (~ (_ < _)%Z) => abstract omega: zarith. -Hint Extern 10 (~ (_ >= _)%Z) => abstract omega: zarith. -Hint Extern 10 (~ (_ > _)%Z) => abstract omega: zarith. - -Hint Extern 10 False => abstract omega: zarith. +Hint Extern 10 (_ = _ :>nat) => abstract lia: zarith. +Hint Extern 10 (_ <= _) => abstract lia: zarith. +Hint Extern 10 (_ < _) => abstract lia: zarith. +Hint Extern 10 (_ >= _) => abstract lia: zarith. +Hint Extern 10 (_ > _) => abstract lia: zarith. + +Hint Extern 10 (_ <> _ :>nat) => abstract lia: zarith. +Hint Extern 10 (~ _ <= _) => abstract lia: zarith. +Hint Extern 10 (~ _ < _) => abstract lia: zarith. +Hint Extern 10 (~ _ >= _) => abstract lia: zarith. +Hint Extern 10 (~ _ > _) => abstract lia: zarith. + +Hint Extern 10 (_ = _ :>Z) => abstract lia: zarith. +Hint Extern 10 (_ <= _)%Z => abstract lia: zarith. +Hint Extern 10 (_ < _)%Z => abstract lia: zarith. +Hint Extern 10 (_ >= _)%Z => abstract lia: zarith. +Hint Extern 10 (_ > _)%Z => abstract lia: zarith. + +Hint Extern 10 (_ <> _ :>Z) => abstract lia: zarith. +Hint Extern 10 (~ (_ <= _)%Z) => abstract lia: zarith. +Hint Extern 10 (~ (_ < _)%Z) => abstract lia: zarith. +Hint Extern 10 (~ (_ >= _)%Z) => abstract lia: zarith. +Hint Extern 10 (~ (_ > _)%Z) => abstract lia: zarith. + +Hint Extern 10 False => abstract lia: zarith. |