1 files changed, 35 insertions, 0 deletions
diff --git a/clib/orderedType.ml b/clib/orderedType.ml
new file mode 100644
index 00000000..922eb76a
--- /dev/null
+++ b/clib/orderedType.ml
@@ -0,0 +1,35 @@
+(************************************************************************)
+(*         *   The Coq Proof Assistant / The Coq Development Team       *)
+(*  v      *   INRIA, CNRS and contributors - Copyright 1999-2018       *)
+(* <O___,, *       (see CREDITS file for the list of authors)           *)
+(*   \VV/  **************************************************************)
+(*    //   *    This file is distributed under the terms of the         *)
+(*         *     GNU Lesser General Public License Version 2.1          *)
+(*         *     (see LICENSE file for the text of the license)         *)
+(************************************************************************)
+
+module type S =
+sig
+  type t
+  val compare : t -> t -> int
+end
+
+module Pair (M:S) (N:S) = struct
+  type t = M.t * N.t
+
+  let compare (a,b) (a',b') =
+    let i = M.compare a a' in
+    if Int.equal i 0 then N.compare b b'
+    else i
+end
+
+module UnorderedPair (M:S) = struct
+  type t = M.t * M.t
+
+  let reorder (a,b as p) =
+    if M.compare a b <= 0 then p else (b,a)
+
+  let compare p p' =
+    let p = reorder p and p' = reorder p' in
+    let module P = Pair(M)(M) in P.compare p p'
+end