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-rw-r--r--doc/changelog/03-notations/11848-nicer-decimal-printing.rst5
-rw-r--r--plugins/syntax/r_syntax.ml35
-rw-r--r--test-suite/output/QArithSyntax.out16
-rw-r--r--test-suite/output/RealSyntax.out18
-rw-r--r--theories/Init/Decimal.v31
-rw-r--r--theories/QArith/QArith_base.v32
6 files changed, 115 insertions, 22 deletions
diff --git a/doc/changelog/03-notations/11848-nicer-decimal-printing.rst b/doc/changelog/03-notations/11848-nicer-decimal-printing.rst
new file mode 100644
index 0000000000..1d3a390f36
--- /dev/null
+++ b/doc/changelog/03-notations/11848-nicer-decimal-printing.rst
@@ -0,0 +1,5 @@
+- **Changed:**
+ Nicer printing for decimal constants in R and Q.
+ 1.5 is now printed 1.5 rather than 15e-1.
+ (`#11848 <https://github.com/coq/coq/pull/11848>`_,
+ by Pierre Roux).
diff --git a/plugins/syntax/r_syntax.ml b/plugins/syntax/r_syntax.ml
index e0dc3d8989..c4e9c8b73d 100644
--- a/plugins/syntax/r_syntax.ml
+++ b/plugins/syntax/r_syntax.ml
@@ -134,7 +134,38 @@ let r_of_rawnum ?loc n =
(* Printing R via scopes *)
(**********************************************************************)
-let rawnum_of_r c = match DAst.get c with
+let rawnum_of_r c =
+ (* print i * 10^e, precondition: e <> 0 *)
+ let numTok_of_int_exp i e =
+ (* choose between 123e-2 and 1.23, this is purely heuristic
+ and doesn't play any soundness role *)
+ let choose_exponent =
+ if Bigint.is_strictly_pos e then
+ true (* don't print 12 * 10^2 as 1200 to distinguish them *)
+ else
+ let i = Bigint.to_string i in
+ let li = if i.[0] = '-' then String.length i - 1 else String.length i in
+ let e = Bigint.neg e in
+ let le = String.length (Bigint.to_string e) in
+ Bigint.(less_than (add (of_int li) (of_int le)) e) in
+ (* print 123 * 10^-2 as 123e-2 *)
+ let numTok_exponent () = NumTok.Signed.of_bigint_and_exponent i e in
+ (* print 123 * 10^-2 as 1.23, precondition e < 0 *)
+ let numTok_dot () =
+ let s, i =
+ if Bigint.is_pos_or_zero i then NumTok.SPlus, Bigint.to_string i
+ else NumTok.SMinus, Bigint.(to_string (neg i)) in
+ let ni = String.length i in
+ let e = - (Bigint.to_int e) in
+ assert (e > 0);
+ let i, f =
+ if e < ni then String.sub i 0 (ni - e), String.sub i (ni - e) e
+ else "0", String.make (e - ni) '0' ^ i in
+ let i = s, NumTok.UnsignedNat.of_string i in
+ let f = NumTok.UnsignedNat.of_string f in
+ NumTok.Signed.of_decimal_and_exponent i (Some f) None in
+ if choose_exponent then numTok_exponent () else numTok_dot () in
+ match DAst.get c with
| GApp (r, [a]) when is_gr r glob_IZR ->
let n = bigint_of_z a in
NumTok.Signed.of_bigint n
@@ -151,7 +182,7 @@ let rawnum_of_r c = match DAst.get c with
let i = bigint_of_z l in
let e = bignat_of_pos e in
let e = if is_gr md glob_Rdiv then neg e else e in
- NumTok.Signed.of_bigint_and_exponent i e
+ numTok_of_int_exp i e
| _ -> raise Non_closed_number
end
| _ -> raise Non_closed_number
diff --git a/test-suite/output/QArithSyntax.out b/test-suite/output/QArithSyntax.out
index 6bc04f1cef..fe6a1d25c6 100644
--- a/test-suite/output/QArithSyntax.out
+++ b/test-suite/output/QArithSyntax.out
@@ -1,14 +1,14 @@
-eq_refl : 102e-2 = 102e-2
- : 102e-2 = 102e-2
-eq_refl : 102e-1 = 102e-1
- : 102e-1 = 102e-1
+eq_refl : 1.02 = 1.02
+ : 1.02 = 1.02
+eq_refl : 10.2 = 10.2
+ : 10.2 = 10.2
eq_refl : 1020 = 1020
: 1020 = 1020
eq_refl : 102 = 102
: 102 = 102
-eq_refl : 102e-2 = 102e-2
- : 102e-2 = 102e-2
+eq_refl : 1.02 = 1.02
+ : 1.02 = 1.02
eq_refl : -1e-4 = -1e-4
: -1e-4 = -1e-4
-eq_refl : -50e-2 = -50e-2
- : -50e-2 = -50e-2
+eq_refl : -0.50 = -0.50
+ : -0.50 = -0.50
diff --git a/test-suite/output/RealSyntax.out b/test-suite/output/RealSyntax.out
index ebc272d9af..1685964b0f 100644
--- a/test-suite/output/RealSyntax.out
+++ b/test-suite/output/RealSyntax.out
@@ -2,21 +2,21 @@
: R
(-31)%R
: R
-15e-1%R
+1.5%R
: R
15%R
: R
-eq_refl : 102e-2 = 102e-2
- : 102e-2 = 102e-2
-eq_refl : 102e-1 = 102e-1
- : 102e-1 = 102e-1
+eq_refl : 1.02 = 1.02
+ : 1.02 = 1.02
+eq_refl : 10.2 = 10.2
+ : 10.2 = 10.2
eq_refl : 102e1 = 102e1
: 102e1 = 102e1
eq_refl : 102 = 102
: 102 = 102
-eq_refl : 102e-2 = 102e-2
- : 102e-2 = 102e-2
+eq_refl : 1.02 = 1.02
+ : 1.02 = 1.02
eq_refl : -1e-4 = -1e-4
: -1e-4 = -1e-4
-eq_refl : -50e-2 = -50e-2
- : -50e-2 = -50e-2
+eq_refl : -0.50 = -0.50
+ : -0.50 = -0.50
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/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.
generated by cgit v1.2.3 (git 2.25.1) at 2026-01-31 15:13:53 +0000