diff --git a/_oasis b/_oasis
index 90e512cb..30340442 100644
--- a/_oasis
+++ b/_oasis
@@ -48,7 +48,7 @@ Flag "advanced"
 Library "containers"
   Path:             src/core
   Modules:          CCVector, CCPrint, CCError, CCHeap, CCList, CCOpt, CCPair,
-                    CCFun, CCHash, CCInt, CCBool, CCFloat, CCArray, CCRef,
+                    CCFun, CCHash, CCInt, CCBool, CCFloat, CCArray, CCRef, CCSet,
                     CCOrd, CCRandom, CCString, CCHashtbl, CCMap, CCFormat
   BuildDepends:     bytes
 
diff --git a/doc/intro.txt b/doc/intro.txt
index 400e2e7c..631dec78 100644
--- a/doc/intro.txt
+++ b/doc/intro.txt
@@ -41,6 +41,7 @@ CCPair
 CCPrint
 CCRandom
 CCRef
+CCSet
 CCString
 CCVector
 }
diff --git a/src/core/CCSet.ml b/src/core/CCSet.ml
new file mode 100644
index 00000000..5abed74a
--- /dev/null
+++ b/src/core/CCSet.ml
@@ -0,0 +1,86 @@
+
+(*
+copyright (c) 2013-2014, simon cruanes
+all rights reserved.
+
+redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+redistributions of source code must retain the above copyright notice, this
+list of conditions and the following disclaimer.  redistributions in binary
+form must reproduce the above copyright notice, this list of conditions and the
+following disclaimer in the documentation and/or other materials provided with
+the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*)
+
+(** {1 Wrapper around Set} *)
+
+type 'a sequence = ('a -> unit) -> unit
+type 'a printer = Buffer.t -> 'a -> unit
+type 'a formatter = Format.formatter -> 'a -> unit
+
+module type S = sig
+  include Set.S
+
+  val of_seq : elt sequence -> t
+
+  val to_seq : t -> elt sequence
+
+  val of_list : elt list -> t
+
+  val to_list : t -> elt list
+
+  val pp : ?start:string -> ?stop:string -> ?sep:string ->
+            elt printer -> t printer
+
+  val print : ?start:string -> ?stop:string -> ?sep:string ->
+              elt formatter -> t formatter
+end
+
+module Make(O : Map.OrderedType) = struct
+  include Set.Make(O)
+
+  let of_seq s =
+    let set = ref empty  in
+    s (fun x -> set := add x !set);
+    !set
+
+  let to_seq s yield = iter yield s
+
+  let of_list l = List.fold_left (fun set x -> add x set) empty l
+
+  let to_list = elements
+
+  let pp ?(start="{") ?(stop="}") ?(sep=", ") pp_x buf m =
+    let first = ref true in
+    Buffer.add_string buf start;
+    iter
+      (fun x ->
+        if !first then first := false else Buffer.add_string buf sep;
+        pp_x buf x;
+      ) m;
+    Buffer.add_string buf stop
+
+  let print ?(start="[") ?(stop="]") ?(sep=", ") pp_x fmt m =
+    Format.pp_print_string fmt start;
+    let first = ref true in
+    iter
+      (fun x ->
+        if !first then first := false else Format.pp_print_string fmt sep;
+        pp_x fmt x;
+        Format.pp_print_cut fmt ()
+      ) m;
+    Format.pp_print_string fmt stop
+end
+
diff --git a/src/core/CCSet.mli b/src/core/CCSet.mli
new file mode 100644
index 00000000..cc396ddc
--- /dev/null
+++ b/src/core/CCSet.mli
@@ -0,0 +1,53 @@
+
+(*
+copyright (c) 2013-2014, simon cruanes
+all rights reserved.
+
+redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+redistributions of source code must retain the above copyright notice, this
+list of conditions and the following disclaimer.  redistributions in binary
+form must reproduce the above copyright notice, this list of conditions and the
+following disclaimer in the documentation and/or other materials provided with
+the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*)
+
+(** {1 Wrapper around Set} *)
+
+type 'a sequence = ('a -> unit) -> unit
+type 'a printer = Buffer.t -> 'a -> unit
+type 'a formatter = Format.formatter -> 'a -> unit
+
+module type S = sig
+  include Set.S
+
+  val of_seq : elt sequence -> t
+
+  val to_seq : t -> elt sequence
+
+  val of_list : elt list -> t
+
+  val to_list : t -> elt list
+
+  val pp : ?start:string -> ?stop:string -> ?sep:string ->
+            elt printer -> t printer
+
+  val print : ?start:string -> ?stop:string -> ?sep:string ->
+              elt formatter -> t formatter
+end
+
+module Make(O : Set.OrderedType) : S
+  with type t = Set.Make(O).t
+  and type elt = O.t