Add sqrt in Numbers

 As for power recently, we add a specification in NZ,N,Z,
 derived properties, implementations for nat, N, Z, BigN, BigZ.

  - For nat, this sqrt is brand new :-), cf NPeano.v

  - For Z, we rework what was in Zsqrt: same algorithm,
    no more refine but a pure function, based now on a sqrt
    for positive, from which we derive a Nsqrt and a Zsqrt.
    For the moment, the old Zsqrt.v file is kept as Zsqrt_compat.v.
    It is not loaded by default by Require ZArith.
    New definitions are now in Psqrt.v, Zsqrt_def.v and Nsqrt_def.v

  - For BigN, BigZ, we changed the specifications to refer to Zsqrt
    instead of using characteristic inequations.

 On the way, many extensions, in particular BinPos (lemmas about order),
 NZMulOrder (results about squares)

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@13564 85f007b7-540e-0410-9357-904b9bb8a0f7

2 files changed, 18 insertions, 4 deletions

diff --git a/theories/Numbers/Integer/SpecViaZ/ZSig.v b/theories/Numbers/Integer/SpecViaZ/ZSig.v
index be201f2d66..37f5b294e1 100644
--- a/theories/Numbers/Integer/SpecViaZ/ZSig.v
+++ b/theories/Numbers/Integer/SpecViaZ/ZSig.v
@@ -78,13 +78,12 @@ Module Type ZType.
  Parameter spec_pow_pos: forall x n, [pow_pos x n] = [x] ^ Zpos n.
  Parameter spec_pow_N: forall x n, [pow_N x n] = [x] ^ Z_of_N n.
  Parameter spec_pow: forall x n, [pow x n] = [x] ^ [n].
- Parameter spec_sqrt: forall x, 0 <= [x] ->
-   [sqrt x] ^ 2 <= [x] < ([sqrt x] + 1) ^ 2.
+ Parameter spec_sqrt: forall x, [sqrt x] = Zsqrt [x].
  Parameter spec_div_eucl: forall x y,
    let (q,r) := div_eucl x y in ([q], [r]) = Zdiv_eucl [x] [y].
  Parameter spec_div: forall x y, [div x y] = [x] / [y].
  Parameter spec_modulo: forall x y, [modulo x y] = [x] mod [y].
- Parameter spec_gcd: forall a b, [gcd a b] = Zgcd (to_Z a) (to_Z b).
+ Parameter spec_gcd: forall a b, [gcd a b] = Zgcd [a] [b].
  Parameter spec_sgn : forall x, [sgn x] = Zsgn [x].
  Parameter spec_abs : forall x, [abs x] = Zabs [x].
  Parameter spec_even : forall x, even x = Zeven_bool [x].
diff --git a/theories/Numbers/Integer/SpecViaZ/ZSigZAxioms.v b/theories/Numbers/Integer/SpecViaZ/ZSigZAxioms.v
index 3e63755434..d632d22607 100644
--- a/theories/Numbers/Integer/SpecViaZ/ZSigZAxioms.v
+++ b/theories/Numbers/Integer/SpecViaZ/ZSigZAxioms.v
@@ -18,7 +18,7 @@ Module ZTypeIsZAxioms (Import Z : ZType').
 
 Hint Rewrite
  spec_0 spec_1 spec_2 spec_add spec_sub spec_pred spec_succ
- spec_mul spec_opp spec_of_Z spec_div spec_modulo
+ spec_mul spec_opp spec_of_Z spec_div spec_modulo spec_sqrt
  spec_compare spec_eq_bool spec_max spec_min spec_abs spec_sgn
  spec_pow spec_even spec_odd
  : zsimpl.
@@ -278,6 +278,21 @@ Proof.
  intros a b. red. now rewrite spec_pow_N, spec_pow_pos.
 Qed.
 
+(** Sqrt *)
+
+Program Instance sqrt_wd : Proper (eq==>eq) sqrt.
+
+Lemma sqrt_spec : forall n, 0<=n ->
+ (sqrt n)*(sqrt n) <= n /\ n < (succ (sqrt n))*(succ (sqrt n)).
+Proof.
+ intros n. zify. apply Zsqrt_spec.
+Qed.
+
+Lemma sqrt_neg : forall n, n<0 -> sqrt n == 0.
+Proof.
+ intros n. zify. apply Zsqrt_neg.
+Qed.
+
 (** Even / Odd *)
 
 Definition Even n := exists m, n == 2*m.