Imported Upstream snapshot 8.3~beta0+13298

1 files changed, 33 insertions, 0 deletions

diff --git a/lib/refutpat.ml4 b/lib/refutpat.ml4
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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        *)
+(************************************************************************)
+
+(*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