Use camlp4 to accept some specific non-exhaustive patterns in groebner

 The camlp4 extension "refutpat" provides a syntax let* for pattern
 that are non-exhaustive on purpose (e.g. let* x::l = foo in ...).
 A Failure is raised if the pattern doesn't match the expression.

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@12245 85f007b7-540e-0410-9357-904b9bb8a0f7

1 files changed, 33 insertions, 0 deletions

diff --git a/lib/refutpat.ml4 b/lib/refutpat.ml4
new file mode 100644
index 0000000000..f2575def43
--- /dev/null
+++ b/lib/refutpat.ml4
@@ -0,0 +1,33 @@
+(************************************************************************)
+(*  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        *)
+(************************************************************************)
+
+(*i camlp4use: "pa_extend.cmo q_MLast.cmo" i*)
+
+open Pcaml
+
+(** * Non-irrefutable patterns
+
+    This small camlp4 extension creates a "let*" variant of the "let"
+    syntax that allow the use of a non-exhaustive pattern. The typical
+    usage is:
+        
+      let* x::l = foo in ...
+
+    when foo is already known to be non-empty. This way, no warnings by ocamlc.
+    A Failure is raised if the pattern doesn't match the expression.
+*)
+
+
+EXTEND
+ expr:
+   [[ "let"; "*"; p = patt; "="; e1 = expr; "in"; e2 = expr ->
+       <:expr< match $e1$ with
+	        [ $p$ -> $e2$
+                | _ -> failwith "Refutable pattern failed"
+                ] >> ]];
+END