diff --git a/_oasis b/_oasis
index 17827688..3fdc7b15 100644
--- a/_oasis
+++ b/_oasis
@@ -49,7 +49,7 @@ Library "containers"
   Path:             src/core
   Modules:          CCVector, CCPrint, CCError, CCHeap, CCList, CCOpt, CCPair,
                     CCFun, CCHash, CCInt, CCBool, CCFloat, CCArray,
-                    CCOrd, CCRandom, CCString, CCHashtbl, CCMap
+                    CCOrd, CCRandom, CCString, CCHashtbl, CCMap, CCFormat
   BuildDepends:     bytes
 
 Library "containers_io"
diff --git a/doc/intro.txt b/doc/intro.txt
index bc686872..570c36a9 100644
--- a/doc/intro.txt
+++ b/doc/intro.txt
@@ -28,6 +28,7 @@ CCBool
 CCError
 CCFloat
 CCFun
+CCFormat
 CCHash
 CCHashtbl
 CCHeap
diff --git a/src/core/CCFormat.ml b/src/core/CCFormat.ml
new file mode 100644
index 00000000..5bff0275
--- /dev/null
+++ b/src/core/CCFormat.ml
@@ -0,0 +1,142 @@
+
+(*
+copyright (c) 2013, 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 Helpers for Format} *)
+
+type 'a sequence = ('a -> unit) -> unit
+
+type t = Format.formatter
+type 'a printer = t -> 'a -> unit
+
+(** {2 Combinators} *)
+
+let silent _fmt _ = ()
+
+let unit fmt () = Format.pp_print_string fmt "()"
+let int fmt i = Format.pp_print_string fmt (string_of_int i)
+let string fmt s = Format.pp_print_string fmt s
+let bool fmt b = Format.fprintf fmt "%B" b
+let float3 fmt f = Format.fprintf fmt "%.3f" f
+let float fmt f = Format.pp_print_string fmt (string_of_float f)
+
+let list ?(start="[") ?(stop="]") ?(sep=", ") pp fmt l =
+  let rec pp_list l = match l with
+  | x::((_::_) as l) ->
+    pp fmt x;
+    Format.pp_print_string fmt sep;
+    Format.pp_print_cut fmt ();
+    pp_list l
+  | x::[] -> pp fmt x
+  | [] -> ()
+  in
+  Format.pp_print_string fmt start;
+  pp_list l;
+  Format.pp_print_string fmt stop
+
+let array ?(start="[") ?(stop="]") ?(sep=", ") pp fmt a =
+  Format.pp_print_string fmt start;
+  for i = 0 to Array.length a - 1 do
+    if i > 0 then (
+      Format.pp_print_string fmt sep;
+      Format.pp_print_cut fmt ();
+    );
+    pp fmt a.(i)
+  done;
+  Format.pp_print_string fmt stop
+
+let arrayi ?(start="[") ?(stop="]") ?(sep=", ") pp fmt a =
+  Format.pp_print_string fmt start;
+  for i = 0 to Array.length a - 1 do
+    if i > 0 then (
+      Format.pp_print_string fmt sep;
+      Format.pp_print_cut fmt ();
+    );
+    pp fmt (i, a.(i))
+  done;
+  Format.pp_print_string fmt stop
+
+let seq ?(start="[") ?(stop="]") ?(sep=", ") pp fmt seq =
+  Format.pp_print_string fmt start;
+  let first = ref true in
+  seq (fun x ->
+    (if !first then first := false else Format.pp_print_string fmt sep);
+    pp fmt x);
+  Format.pp_print_string fmt stop
+
+let opt pp fmt x = match x with
+  | None -> Format.pp_print_string fmt "none"
+  | Some x -> Format.fprintf fmt "some %a" pp x
+
+let pair ppa ppb fmt (a, b) =
+  Format.fprintf fmt "(%a, %a)" ppa a ppb b
+
+let triple ppa ppb ppc fmt (a, b, c) =
+  Format.fprintf fmt "(%a, %a, %a)" ppa a ppb b ppc c
+
+let quad ppa ppb ppc ppd fmt (a, b, c, d) =
+  Format.fprintf fmt "(%a, %a, %a, %a)" ppa a ppb b ppc c ppd d
+
+let map f pp fmt x =
+  pp fmt (f x);
+  ()
+
+(** {2 IO} *)
+
+let output fmt pp x = pp fmt x
+
+let to_string pp x =
+  let buf = Buffer.create 64 in
+  let fmt = Format.formatter_of_buffer buf in
+  pp fmt x;
+  Format.pp_print_flush fmt ();
+  Buffer.contents buf
+
+let sprintf format =
+  let buf = Buffer.create 64 in
+  let fmt = Format.formatter_of_buffer buf in
+  Format.kfprintf
+    (fun _fmt -> Format.pp_print_flush fmt (); Buffer.contents buf)
+    fmt
+    format
+
+let stdout = Format.std_formatter
+let stderr = Format.err_formatter
+
+let _with_file_out filename f =
+  let oc = open_out filename in
+  let fmt = Format.formatter_of_out_channel oc in
+  begin try
+    let x = f fmt in
+    Format.pp_print_flush fmt ();
+    x
+  with e ->
+    Format.pp_print_flush fmt ();
+    close_out_noerr oc;
+    raise e
+  end
+
+let to_file filename format =
+  _with_file_out filename (fun fmt -> Format.fprintf fmt format)
diff --git a/src/core/CCFormat.mli b/src/core/CCFormat.mli
new file mode 100644
index 00000000..d8c06657
--- /dev/null
+++ b/src/core/CCFormat.mli
@@ -0,0 +1,73 @@
+
+(*
+copyright (c) 2013, 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 Helpers for Format}
+
+@since NEXT_RELEASE *)
+
+type 'a sequence = ('a -> unit) -> unit
+
+type t = Format.formatter
+type 'a printer = t -> 'a -> unit
+
+(** {2 Combinators} *)
+
+val silent : 'a printer (** prints nothing *)
+
+val unit : unit printer
+val int : int printer
+val string : string printer
+val bool : bool printer
+val float3 : float printer (* 3 digits after . *)
+val float : float printer
+
+val list : ?start:string -> ?stop:string -> ?sep:string -> 'a printer -> 'a list printer
+val array : ?start:string -> ?stop:string -> ?sep:string -> 'a printer -> 'a array printer
+val arrayi : ?start:string -> ?stop:string -> ?sep:string ->
+            (int * 'a) printer -> 'a array printer
+val seq : ?start:string -> ?stop:string -> ?sep:string -> 'a printer -> 'a sequence printer
+
+val opt : 'a printer -> 'a option printer
+
+val pair : 'a printer -> 'b printer -> ('a * 'b) printer
+val triple : 'a printer -> 'b printer -> 'c printer -> ('a * 'b * 'c) printer
+val quad : 'a printer -> 'b printer -> 'c printer -> 'd printer -> ('a * 'b * 'c * 'd) printer
+
+val map : ('a -> 'b) -> 'b printer -> 'a printer
+
+(** {2 IO} *)
+
+val output : t -> 'a printer -> 'a -> unit
+val to_string : 'a printer -> 'a -> string
+
+val stdout : t
+val stderr : t
+
+val sprintf : ('a, t, unit, string) format4 -> 'a
+  (** print into a string *)
+
+val to_file : string -> ('a, t, unit, unit) format4 -> 'a
+  (** Print to the given file *)
diff --git a/src/core/CCPrint.ml b/src/core/CCPrint.ml
index 8ccde136..4b936a7e 100644
--- a/src/core/CCPrint.ml
+++ b/src/core/CCPrint.ml
@@ -59,7 +59,7 @@ let list ?(start="[") ?(stop="]") ?(sep=", ") pp buf l =
   Buffer.add_string buf start;
   pp_list l;
   Buffer.add_string buf stop
-  
+
 let array ?(start="[") ?(stop="]") ?(sep=", ") pp buf a =
   Buffer.add_string buf start;
   for i = 0 to Array.length a - 1 do
@@ -67,7 +67,7 @@ let array ?(start="[") ?(stop="]") ?(sep=", ") pp buf a =
     pp buf a.(i)
   done;
   Buffer.add_string buf stop
-  
+
 let arrayi ?(start="[") ?(stop="]") ?(sep=", ") pp buf a =
   Buffer.add_string buf start;
   for i = 0 to Array.length a - 1 do