diff --git a/.ocamlinit b/.ocamlinit
index f2acb85d..f477d71c 100644
--- a/.ocamlinit
+++ b/.ocamlinit
@@ -2,8 +2,10 @@
 #thread
 #directory "_build/core";;
 #directory "_build/misc";;
+#directory "_build/string";;
 #directory "_build/tests/";;
 #load "containers.cma";;
+#load "containers_string.cma";;
 #load "containers_misc.cma";;
 #require "threads";;
 #load "containers_thread.cma";;
diff --git a/Makefile b/Makefile
index 90956761..3a121ca2 100644
--- a/Makefile
+++ b/Makefile
@@ -54,6 +54,7 @@ DONTTEST=myocamlbuild.ml setup.ml
 QTESTABLE=$(filter-out $(DONTTEST), \
 	$(wildcard core/*.ml) $(wildcard core/*.mli) \
 	$(wildcard misc/*.ml) $(wildcard misc/*.mli) \
+	$(wildcard string/*.ml) $(wildcard string/*.mli) \
 	)
 
 qtest-clean:
@@ -62,7 +63,9 @@ qtest-clean:
 qtest: qtest-clean build
 	@mkdir -p qtest
 	@qtest extract -o qtest/qtest_all.ml $(QTESTABLE) 2> /dev/null
-	@ocamlbuild $(OPTIONS) -pkg oUnit,QTest2Lib -I core -I misc qtest/qtest_all.native
+	@ocamlbuild $(OPTIONS) -pkg oUnit,QTest2Lib \
+		-I core -I misc -I string \
+		qtest/qtest_all.native
 	@echo
 	./qtest_all.native
 
diff --git a/_oasis b/_oasis
index 255b7395..982f3d63 100644
--- a/_oasis
+++ b/_oasis
@@ -46,7 +46,7 @@ Library "containers"
 Library "containers_string"
   Path:             string
   Pack:             true
-  Modules:          KMP
+  Modules:          KMP, CCString, Levenshtein
   FindlibName:      string
   FindlibParent:    containers
 
@@ -59,7 +59,7 @@ Library "containers_misc"
                     Bij, PiCalculus, Bencode, Sexp, RAL,
                     UnionFind, SmallSet, AbsSet, CSM,
                     ActionMan, QCheck, BencodeOnDisk, TTree,
-                    HGraph, Automaton, Conv, Levenshtein, Bidir, Iteratee,
+                    HGraph, Automaton, Conv, Bidir, Iteratee,
                     Ty, Tell, BencodeStream, RatTerm, Cause
   BuildDepends:     unix,containers
   FindlibName:      misc
@@ -102,7 +102,15 @@ Document containers
   BuildTools+:          ocamldoc
   Install:              true
   XOCamlbuildPath:      .
-  XOCamlbuildLibraries: containers
+  XOCamlbuildLibraries: containers,containers.string
+
+Document containers_misc
+  Title:                Containers_misc docs
+  Type:                 ocamlbuild (0.3)
+  BuildTools+:          ocamldoc
+  Install:              true
+  XOCamlbuildPath:      .
+  XOCamlbuildLibraries: containers.misc
 
 Executable benchs
   Path:             tests/
@@ -110,7 +118,7 @@ Executable benchs
   CompiledObject:   native
   Build$:           flag(bench)
   MainIs:           benchs.ml
-  BuildDepends:     containers,containers.misc,bench
+  BuildDepends:     containers,containers.string,containers.misc,bench
 
 Executable bench_conv
   Path: tests/
diff --git a/_tags b/_tags
index 988b9a40..94f7bebc 100644
--- a/_tags
+++ b/_tags
@@ -125,3 +125,4 @@
 # OASIS_STOP
 <tests/*.ml{,i}>: thread
 <threads/*.ml{,i}>: thread
+<**/*.ml>: warn_K, warn_Y, warn_X
diff --git a/core/CCFun.ml b/core/CCFun.ml
index ba6173d5..2a675b42 100644
--- a/core/CCFun.ml
+++ b/core/CCFun.ml
@@ -37,3 +37,12 @@ let (%) f g x = f (g x)
 let lexicographic f1 f2 x y =
   let c = f1 x y in
   if c <> 0 then c else f2 x y
+
+let finally ~h ~f =
+  try
+    let x = f () in
+    h ();
+    x
+  with e ->
+    h ();
+    raise e
diff --git a/core/CCFun.mli b/core/CCFun.mli
index aa0010e1..dc3085a5 100644
--- a/core/CCFun.mli
+++ b/core/CCFun.mli
@@ -40,3 +40,8 @@ val (%) : ('b -> 'c) -> ('a -> 'b) -> 'a -> 'c
 
 val lexicographic : ('a -> 'a -> int) -> ('a -> 'a -> int) -> 'a -> 'a -> int
 (** Lexicographic combination of comparison functions *)
+
+val finally : h:(unit -> unit) -> f:(unit -> 'a) -> 'a
+  (** [finally h f] calls [f ()] and returns its result. If it raises, the
+      same exception is raised; in {b any} case, [h ()] is called after
+      [f ()] terminates. *)
diff --git a/string/CCString.ml b/string/CCString.ml
new file mode 100644
index 00000000..e21225a1
--- /dev/null
+++ b/string/CCString.ml
@@ -0,0 +1,144 @@
+
+(*
+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 Basic String Utils} *)
+
+type t = string
+
+type 'a gen = unit -> 'a option
+type 'a sequence = ('a -> unit) -> unit
+
+let is_sub ~sub i s j =
+  let rec check k =
+    if i + k = String.length sub
+      then true
+      else sub.[i + k] = s.[j+k] && check (k+1)
+  in
+  check 0
+
+(* note: quite inefficient if [by] is long *)
+let split_gen ~by s =
+  let len_by = String.length by in
+  assert (len_by > 0);
+  let n = String.length s in
+  let prev = ref 0 in
+  let stop = ref false in
+  let rec search i =
+    if !stop then None
+    else if i >= n
+      then (
+        stop := true;
+        Some (String.sub s !prev (n- !prev))  (* done *)
+      )
+    else if is_prefix i 0
+      then (
+        let p = !prev in
+        prev := i+len_by;
+        Some (String.sub s p (i-p))
+      )
+    else search (i+1)
+  and is_prefix i j =
+    if j = len_by
+      then true
+    else if i = n
+      then false
+    else s.[i] = by.[j] && is_prefix (i+1) (j+1)
+  in
+  fun () ->
+    search !prev
+
+let split_seq ~by s k =
+  let rec aux g = match g () with
+    | None -> ()
+    | Some x -> k x; aux g
+  in aux (split_gen ~by s)
+
+let split ~by s =
+  let rec aux g acc = match g () with
+    | None -> List.rev acc
+    | Some x -> aux g (x::acc)
+  in aux (split_gen ~by s) []
+
+(*$T
+  split ~by:"," "aa,bb,cc" = ["aa"; "bb"; "cc"]
+  split ~by:"--" "a--b----c--" = ["a"; "b"; ""; "c"; ""]
+*)
+
+(* note: inefficient *)
+let find ?(start=0) ~sub s =
+  let n = String.length sub in
+  let i = ref start in
+  try
+    while !i + n < String.length s do
+      if is_sub ~sub 0 s !i then raise Exit;
+      incr i
+    done;
+    -1
+  with Exit ->
+    !i
+
+let repeat s n =
+  assert (n>=0);
+  let len = String.length s in
+  assert(len > 0);
+  let buf = String.create (len * n) in
+  for i = 0 to n-1 do
+    String.blit s 0 buf (i * len) len;
+  done;
+  buf
+
+let prefix ~pre s =
+  String.length pre <= String.length s &&
+  (let i = ref 0 in
+    while !i < String.length pre && s.[!i] = pre.[!i] do incr i done;
+    !i = String.length pre)
+
+
+let to_gen s =
+  let i = ref 0 in
+  fun () ->
+    if !i = String.length s then None
+    else (
+      let c = String.unsafe_get s !i in
+      incr i;
+      Some c
+    )
+
+let of_gen g =
+  let b = Buffer.create 32 in
+  let rec aux () = match g () with
+    | None -> Buffer.contents b
+    | Some c -> Buffer.add_char b c; aux ()
+  in aux ()
+
+let to_seq s k = String.iter k s
+
+let of_seq seq =
+  let b= Buffer.create 32 in
+  seq (Buffer.add_char b);
+  Buffer.contents b
+
+let pp = Buffer.add_string
diff --git a/string/CCString.mli b/string/CCString.mli
new file mode 100644
index 00000000..a3938e1b
--- /dev/null
+++ b/string/CCString.mli
@@ -0,0 +1,64 @@
+
+(*
+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 Basic String Utils}
+Consider using KMP instead. *)
+
+type t = string
+
+type 'a gen = unit -> 'a option
+type 'a sequence = ('a -> unit) -> unit
+
+val is_sub : sub:t -> int -> t -> int -> bool
+(** [is_sub ~sub i s j] returns [true] iff [sub] is a substring of [s] starting
+    at position [j] *)
+
+val split : by:t -> t -> t list
+(** split the given string along the given separator [by]. Should only
+    be used with very small separators, otherwise use {!KMP}.
+    @raise Failure if [by = ""] *)
+
+val split_gen : by:t -> t -> t gen
+
+val split_seq : by:t -> t -> t sequence
+
+val find : ?start:int -> sub:t -> t -> int
+(** Find [sub] in the string, returns its first index or -1.
+    Should only be used with very small [sub] *)
+
+val repeat : t -> int -> t
+(** The same string, repeated n times *)
+
+val prefix : pre:t -> t -> bool
+(** [str_prefix ~pre s] returns [true] iff [pre] is a prefix of [s] *)
+
+val to_gen : t -> char gen
+val of_gen : char gen -> t
+
+val to_seq : t -> char sequence
+val of_seq : char sequence -> t
+
+val pp : Buffer.t -> t -> unit
diff --git a/string/KMP.ml b/string/KMP.ml
index a49ce282..092528bb 100644
--- a/string/KMP.ml
+++ b/string/KMP.ml
@@ -167,7 +167,7 @@ module Make(Str : STRING) = struct
     seq ~pattern:(compile pattern) s 0
 end
 
-module Default = Make(struct
+include  Make(struct
   type char_ = char
   type char = char_
   type t = string
diff --git a/string/KMP.mli b/string/KMP.mli
index f431137a..49ba791c 100644
--- a/string/KMP.mli
+++ b/string/KMP.mli
@@ -72,4 +72,4 @@ end
 
 module Make(Str : STRING) : S with type string = Str.t
 
-module Default : S with type string = string
+include S with type string = string
diff --git a/misc/levenshtein.ml b/string/levenshtein.ml
similarity index 100%
rename from misc/levenshtein.ml
rename to string/levenshtein.ml
diff --git a/misc/levenshtein.mli b/string/levenshtein.mli
similarity index 100%
rename from misc/levenshtein.mli
rename to string/levenshtein.mli