Ajout de la fonction [subset].

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@1519 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02

stdlib/set.ml

@@ -33,6 +33,7 @@ module type S =
     val diff: t -> t -> t
     val compare: t -> t -> int
     val equal: t -> t -> bool
+    val subset: t -> t -> bool
     val iter: (elt -> 'a) -> t -> unit
     val fold: (elt -> 'a -> 'a) -> t -> 'a -> 'a
     val cardinal: t -> int
@@ -217,6 +218,21 @@ module Make(Ord: OrderedType) =
     let equal s1 s2 =
       compare s1 s2 = 0
 
+    let rec subset s1 s2 =
+      match (s1, s2) with
+        Empty, _ ->
+          true
+      | _, Empty ->
+          false
+      | Node (l1, v1, r1, _), (Node (l2, v2, r2, _) as t2) ->
+          let c = Ord.compare v1 v2 in
+          if c = 0 then
+            subset l1 l2 && subset r1 r2
+          else if c < 0 then
+            subset (Node (l1, v1, Empty, 0)) l2 && subset r1 t2
+          else
+            subset (Node (Empty, v1, r1, 0)) r2 && subset l1 t2
+
     let rec iter f = function
         Empty -> ()
       | Node(l, v, r, _) -> iter f l; f v; iter f r

stdlib/set.mli

@@ -64,6 +64,9 @@ module type S =
     val equal: t -> t -> bool
         (* [equal s1 s2] tests whether the sets [s1] and [s2] are
            equal, that is, contain the same elements. *)
+    val subset: t -> t -> bool
+        (* [subset s1 s2] tests whether the set [s1] is a subset of
+           the set [s2]. *)
     val iter: (elt -> 'a) -> t -> unit
         (* [iter f s] applies [f] in turn to all elements of [s], and
            discards the results. The elements of [s] are presented to [f]