Extraction: attempt to provide nice extraction of chars and strings for Ocaml

 When Requiring ExtrOcamlString :

 * ascii is mapped to Ocaml's char, the ugly translation of constructor
 and pattern-match should hopefully be seen very rarely (never ?).
 We add a hack in ocaml.ml for recognizing constant chars.

 * string is mapped to (list char). Extracting to Ocaml's string could be
 done, but would be really nasty (lots of non-trivial Extract Constant to
 add). For now, (list char) seems a good compromise.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@13078 85f007b7-540e-0410-9357-904b9bb8a0f7

1 files changed, 38 insertions, 0 deletions

diff --git a/plugins/extraction/ExtrOcamlString.v b/plugins/extraction/ExtrOcamlString.v
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+++ b/plugins/extraction/ExtrOcamlString.v
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+(************************************************************************)
+(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
+(* <O___,, * CNRS-Ecole Polytechnique-INRIA Futurs-Universite Paris Sud *)
+(*   \VV/  **************************************************************)
+(*    //   *      This file is distributed under the terms of the       *)
+(*         *       GNU Lesser General Public License Version 2.1        *)
+(************************************************************************)
+
+(* Extraction to Ocaml : special handling of ascii and strings *)
+
+Require Import Ascii String.
+
+Extract Inductive ascii => char
+[
+"(* If this appears, you're using Ascii internals. Please don't *)
+ (fun (b0,b1,b2,b3,b4,b5,b6,b7) ->
+  let f b i = if b then 1 lsl i else 0 in
+  Char.chr (f b0 0 + f b1 1 + f b2 2 + f b3 3 + f b4 4 + f b5 5 + f b6 6 + f b7 7))"
+]
+"(* If this appears, you're using Ascii internals. Please don't *)
+ (fun f c ->
+  let n = Char.code c in
+  let h i = (n land (1 lsl i)) <> 0 in
+  f (h 0) (h 1) (h 2) (h 3) (h 4) (h 5) (h 6) (h 7))".
+
+Extract Constant zero => "'\000'".
+Extract Constant one => "'\001'".
+Extract Constant shift =>
+ "fun b c -> Char.chr (((Char.code c) lsl 1) land 255 + if b then 1 else 0)".
+
+Extract Inlined Constant ascii_dec => "(=)".
+
+Extract Inductive string => "list char" [ "[]" "(::)" ].
+
+(*
+Definition test := "ceci est un test"%string.
+Recursive Extraction test Ascii.zero Ascii.one.
+*)