diff --git a/CHANGELOG.adoc b/CHANGELOG.adoc
index 0afdf806..677e85ba 100644
--- a/CHANGELOG.adoc
+++ b/CHANGELOG.adoc
@@ -1,8 +1,19 @@
 = Changelog
 
+== 0.18
+
+- update implem of `CCVector.equal`
+- add `CCOpt.get_or` with label, deprecates `get`
+- add `CCArray.get_safe` (close #70)
+- add `CCGraph.is_dag`
+- add aliases to deprecated  functions from `String`, add `Fun.opaque_identity`
+- add `CCLazy_list.take`
+- add `Lazy_list.filter`
+- add CCList.range_by
+
 == 0.17
 
-=== potentially breaking 
+=== potentially breaking
 
 - change the semantics of `CCString.find_all` (allow overlaps)
 
diff --git a/HOWTO.adoc b/HOWTO.adoc
index 528d72e8..de85e04c 100644
--- a/HOWTO.adoc
+++ b/HOWTO.adoc
@@ -16,7 +16,8 @@ can be removed.
 8. `git merge master`
 9. `oasis setup; make test doc`
 10. tag, and push both to github
-11. new opam package
+11. `opam pin https://github.com/c-cube/ocaml-containers#<release>`
+12. new opam package: `opam publish prepare; opam publish submit`
 
 == List Authors
 
diff --git a/README.adoc b/README.adoc
index 8787436d..b0180351 100644
--- a/README.adoc
+++ b/README.adoc
@@ -2,10 +2,11 @@
 :toc: macro
 :source-highlighter: pygments
 
-image::media/logo.png[logo]
-
 What is _containers_? (take a look at the link:TUTORIAL.adoc[tutorial]!
 or the http://cedeela.fr/~simon/software/containers[documentation])
+In `containers` and `containers.data`, all modules abide by
+_pay for what you use_: only modules that are used are linked (there are no
+cross-module dependencies).
 
 - A usable, reasonably well-designed library that extends OCaml's standard
   library (in 'src/core/', packaged under `containers` in ocamlfind. Modules
@@ -42,6 +43,8 @@ image:https://ci.cedeela.fr/buildStatus/icon?job=containers[alt="Build Status",
 
 toc::[]
 
+image::media/logo.png[logo]
+
 == Change Log
 
 See link:CHANGELOG.adoc[this file].
@@ -268,3 +271,6 @@ A few guidelines:
 
 Powered by image:http://oasis.forge.ocamlcore.org/oasis-badge.png[alt="OASIS", style="border: none;", link="http://oasis.forge.ocamlcore.org/"]
 
+== Documentation by version
+
+- http://c-cube.github.io/ocaml-containers/0.17/[0.17]
diff --git a/_oasis b/_oasis
index 230391b9..b8d14103 100644
--- a/_oasis
+++ b/_oasis
@@ -1,6 +1,6 @@
 OASISFormat: 0.4
 Name:        containers
-Version:     0.17
+Version:     0.18
 Homepage:    https://github.com/c-cube/ocaml-containers
 Authors:     Simon Cruanes
 License:     BSD-2-clause
@@ -40,7 +40,7 @@ Flag "bigarray"
   Default:      true
 
 Flag "advanced"
-  Description:  Build advanced combinators, including CCLinq (requires "sequence")
+  Description:  Build advanced combinators (requires "sequence")
   Default:      true
 
 Library "containers"
diff --git a/doc/intro.txt b/doc/intro.txt
index 6e69309d..b4b2bd73 100644
--- a/doc/intro.txt
+++ b/doc/intro.txt
@@ -22,6 +22,8 @@ by ocamlfind).
 
 {4 Core Modules (extension of the standard library)}
 
+{b findlib name}: containers
+
 {!modules:
 CCArray
 CCBool
@@ -63,6 +65,8 @@ such as:
 
 {4 Containers.data}
 
+{b findlib name}: containers.data
+
 Various data structures.
 
 {!modules:
@@ -123,6 +127,8 @@ CCLazy_list}
 
 {4 String}
 
+{b findlib name}: containers.string
+
 {!modules:
 CCApp_parse
 CCKMP
@@ -139,6 +145,8 @@ Use bigarrays to hold large strings and map files directly into memory.
 
 {4 Advanced}
 
+{b findlib name}: containers.advanced
+
 This module is qualified with [Containers_advanced]. It
 requires {{:https://github.com/c-cube/sequence} Sequence}.
 
@@ -152,7 +160,11 @@ Moved to its own repository.
 
 Moved to its own repository
 
-{4 Others}
+{4 Thread Helpers}
+
+{b findlib name}: containers.thread
+
+Modules related to the use of [Thread].
 
 {!modules:
 CCBlockingQueue
diff --git a/myocamlbuild.ml b/myocamlbuild.ml
index f6541c4b..88d76fbe 100644
--- a/myocamlbuild.ml
+++ b/myocamlbuild.ml
@@ -1,5 +1,5 @@
 (* OASIS_START *)
-(* DO NOT EDIT (digest: b119194f5742ac2f3cdceac9a223dda7) *)
+(* DO NOT EDIT (digest: 9ba607f1a3e839f1c1e8ea449ddfab16) *)
 module OASISGettext = struct
 (* # 22 "src/oasis/OASISGettext.ml" *)
 
@@ -29,6 +29,166 @@ module OASISGettext = struct
 
 end
 
+module OASISString = struct
+(* # 22 "src/oasis/OASISString.ml" *)
+
+
+  (** Various string utilities.
+
+      Mostly inspired by extlib and batteries ExtString and BatString libraries.
+
+      @author Sylvain Le Gall
+    *)
+
+
+  let nsplitf str f =
+    if str = "" then
+      []
+    else
+      let buf = Buffer.create 13 in
+      let lst = ref [] in
+      let push () =
+        lst := Buffer.contents buf :: !lst;
+        Buffer.clear buf
+      in
+      let str_len = String.length str in
+        for i = 0 to str_len - 1 do
+          if f str.[i] then
+            push ()
+          else
+            Buffer.add_char buf str.[i]
+        done;
+        push ();
+        List.rev !lst
+
+
+  (** [nsplit c s] Split the string [s] at char [c]. It doesn't include the
+      separator.
+    *)
+  let nsplit str c =
+    nsplitf str ((=) c)
+
+
+  let find ~what ?(offset=0) str =
+    let what_idx = ref 0 in
+    let str_idx = ref offset in
+      while !str_idx < String.length str &&
+            !what_idx < String.length what do
+        if str.[!str_idx] = what.[!what_idx] then
+          incr what_idx
+        else
+          what_idx := 0;
+        incr str_idx
+      done;
+      if !what_idx <> String.length what then
+        raise Not_found
+      else
+        !str_idx - !what_idx
+
+
+  let sub_start str len =
+    let str_len = String.length str in
+    if len >= str_len then
+      ""
+    else
+      String.sub str len (str_len - len)
+
+
+  let sub_end ?(offset=0) str len =
+    let str_len = String.length str in
+    if len >= str_len then
+      ""
+    else
+      String.sub str 0 (str_len - len)
+
+
+  let starts_with ~what ?(offset=0) str =
+    let what_idx = ref 0 in
+    let str_idx = ref offset in
+    let ok = ref true in
+      while !ok &&
+            !str_idx < String.length str &&
+            !what_idx < String.length what do
+        if str.[!str_idx] = what.[!what_idx] then
+          incr what_idx
+        else
+          ok := false;
+        incr str_idx
+      done;
+      if !what_idx = String.length what then
+        true
+      else
+        false
+
+
+  let strip_starts_with ~what str =
+    if starts_with ~what str then
+      sub_start str (String.length what)
+    else
+      raise Not_found
+
+
+  let ends_with ~what ?(offset=0) str =
+    let what_idx = ref ((String.length what) - 1) in
+    let str_idx = ref ((String.length str) - 1) in
+    let ok = ref true in
+      while !ok &&
+            offset <= !str_idx &&
+            0 <= !what_idx do
+        if str.[!str_idx] = what.[!what_idx] then
+          decr what_idx
+        else
+          ok := false;
+        decr str_idx
+      done;
+      if !what_idx = -1 then
+        true
+      else
+        false
+
+
+  let strip_ends_with ~what str =
+    if ends_with ~what str then
+      sub_end str (String.length what)
+    else
+      raise Not_found
+
+
+  let replace_chars f s =
+    let buf = Buffer.create (String.length s) in
+    String.iter (fun c -> Buffer.add_char buf (f c)) s;
+    Buffer.contents buf
+
+  let lowercase_ascii =
+    replace_chars
+      (fun c ->
+         if (c >= 'A' && c <= 'Z') then
+           Char.chr (Char.code c + 32)
+         else
+           c)
+
+  let uncapitalize_ascii s =
+    if s <> "" then
+      (lowercase_ascii (String.sub s 0 1)) ^ (String.sub s 1 ((String.length s) - 1))
+    else
+      s
+
+  let uppercase_ascii =
+    replace_chars
+      (fun c ->
+         if (c >= 'a' && c <= 'z') then
+           Char.chr (Char.code c - 32)
+         else
+           c)
+
+  let capitalize_ascii s =
+    if s <> "" then
+      (uppercase_ascii (String.sub s 0 1)) ^ (String.sub s 1 ((String.length s) - 1))
+    else
+      s
+
+end
+
 module OASISExpr = struct
 (* # 22 "src/oasis/OASISExpr.ml" *)
 
@@ -129,7 +289,7 @@ module OASISExpr = struct
 end
 
 
-# 132 "myocamlbuild.ml"
+# 292 "myocamlbuild.ml"
 module BaseEnvLight = struct
 (* # 22 "src/base/BaseEnvLight.ml" *)
 
@@ -234,7 +394,7 @@ module BaseEnvLight = struct
 end
 
 
-# 237 "myocamlbuild.ml"
+# 397 "myocamlbuild.ml"
 module MyOCamlbuildFindlib = struct
 (* # 22 "src/plugins/ocamlbuild/MyOCamlbuildFindlib.ml" *)
 
@@ -516,7 +676,7 @@ module MyOCamlbuildBase = struct
                  | nm, [], intf_modules ->
                      ocaml_lib nm;
                      let cmis =
-                       List.map (fun m -> (String.uncapitalize m) ^ ".cmi")
+                       List.map (fun m -> (OASISString.uncapitalize_ascii m) ^ ".cmi")
                                 intf_modules in
                      dep ["ocaml"; "link"; "library"; "file:"^nm^".cma"] cmis
                  | nm, dir :: tl, intf_modules ->
@@ -529,7 +689,7 @@ module MyOCamlbuildBase = struct
                             ["compile"; "infer_interface"; "doc"])
                        tl;
                      let cmis =
-                       List.map (fun m -> dir^"/"^(String.uncapitalize m)^".cmi")
+                       List.map (fun m -> dir^"/"^(OASISString.uncapitalize_ascii m)^".cmi")
                                 intf_modules in
                      dep ["ocaml"; "link"; "library"; "file:"^dir^"/"^nm^".cma"]
                          cmis)
@@ -603,7 +763,7 @@ module MyOCamlbuildBase = struct
 end
 
 
-# 606 "myocamlbuild.ml"
+# 766 "myocamlbuild.ml"
 open Ocamlbuild_plugin;;
 let package_default =
   {
@@ -669,7 +829,7 @@ let conf = {MyOCamlbuildFindlib.no_automatic_syntax = false}
 
 let dispatch_default = MyOCamlbuildBase.dispatch_default conf package_default;;
 
-# 673 "myocamlbuild.ml"
+# 833 "myocamlbuild.ml"
 (* OASIS_STOP *)
 let doc_intro = "doc/intro.txt" ;;
 
diff --git a/opam b/opam
index 679e5df9..1185f504 100644
--- a/opam
+++ b/opam
@@ -26,6 +26,7 @@ remove: [
 ]
 depends: [
     "ocamlfind" {build}
+    "oasis" {build}
     "base-bytes"
     "result"
     "cppo" {build}
diff --git a/setup.ml b/setup.ml
index 46f2f0f3..f9920ad2 100644
--- a/setup.ml
+++ b/setup.ml
@@ -1,9 +1,9 @@
 (* setup.ml generated for the first time by OASIS v0.4.4 *)
 
 (* OASIS_START *)
-(* DO NOT EDIT (digest: 93504d34b391fe80e66c77fd2e99f4e0) *)
+(* DO NOT EDIT (digest: 935c9eb827a9a1a9b4de988f1afb58dd) *)
 (*
-   Regenerated by OASIS v0.4.5
+   Regenerated by OASIS v0.4.6
    Visit http://oasis.forge.ocamlcore.org for more information and
    documentation about functions used in this file.
 *)
@@ -246,6 +246,33 @@ module OASISString = struct
     String.iter (fun c -> Buffer.add_char buf (f c)) s;
     Buffer.contents buf
 
+  let lowercase_ascii =
+    replace_chars
+      (fun c ->
+         if (c >= 'A' && c <= 'Z') then
+           Char.chr (Char.code c + 32)
+         else
+           c)
+
+  let uncapitalize_ascii s =
+    if s <> "" then
+      (lowercase_ascii (String.sub s 0 1)) ^ (String.sub s 1 ((String.length s) - 1))
+    else
+      s
+
+  let uppercase_ascii =
+    replace_chars
+      (fun c ->
+         if (c >= 'a' && c <= 'z') then
+           Char.chr (Char.code c - 32)
+         else
+           c)
+
+  let capitalize_ascii s =
+    if s <> "" then
+      (uppercase_ascii (String.sub s 0 1)) ^ (String.sub s 1 ((String.length s) - 1))
+    else
+      s
 
 end
 
@@ -315,19 +342,15 @@ module OASISUtils = struct
 
 
   let compare_csl s1 s2 =
-    String.compare (String.lowercase s1) (String.lowercase s2)
+    String.compare (OASISString.lowercase_ascii s1) (OASISString.lowercase_ascii s2)
 
 
   module HashStringCsl =
     Hashtbl.Make
       (struct
          type t = string
-
-         let equal s1 s2 =
-             (String.lowercase s1) = (String.lowercase s2)
-
-         let hash s =
-           Hashtbl.hash (String.lowercase s)
+         let equal s1 s2 = (compare_csl s1 s2) = 0
+         let hash s = Hashtbl.hash (OASISString.lowercase_ascii s)
        end)
 
   module SetStringCsl =
@@ -365,7 +388,7 @@ module OASISUtils = struct
           else
             buf
         in
-          String.lowercase buf
+          OASISString.lowercase_ascii buf
       end
 
 
@@ -471,7 +494,7 @@ module PropList = struct
         order     = Queue.create ();
         name_norm =
           (if case_insensitive then
-             String.lowercase
+             OASISString.lowercase_ascii
            else
              fun s -> s);
       }
@@ -1822,13 +1845,13 @@ module OASISUnixPath = struct
   let capitalize_file f =
     let dir = dirname f in
     let base = basename f in
-    concat dir (String.capitalize base)
+    concat dir (OASISString.capitalize_ascii base)
 
 
   let uncapitalize_file f =
     let dir = dirname f in
     let base = basename f in
-    concat dir (String.uncapitalize base)
+    concat dir (OASISString.uncapitalize_ascii base)
 
 
 end
@@ -2890,7 +2913,7 @@ module OASISFileUtil = struct
 end
 
 
-# 2893 "setup.ml"
+# 2916 "setup.ml"
 module BaseEnvLight = struct
 (* # 22 "src/base/BaseEnvLight.ml" *)
 
@@ -2995,7 +3018,7 @@ module BaseEnvLight = struct
 end
 
 
-# 2998 "setup.ml"
+# 3021 "setup.ml"
 module BaseContext = struct
 (* # 22 "src/base/BaseContext.ml" *)
 
@@ -5406,7 +5429,7 @@ module BaseSetup = struct
 end
 
 
-# 5409 "setup.ml"
+# 5432 "setup.ml"
 module InternalConfigurePlugin = struct
 (* # 22 "src/plugins/internal/InternalConfigurePlugin.ml" *)
 
@@ -5845,8 +5868,8 @@ module InternalInstallPlugin = struct
     let make_fnames modul sufx =
       List.fold_right
         begin fun sufx accu ->
-          (String.capitalize modul ^ sufx) ::
-          (String.uncapitalize modul ^ sufx) ::
+          (OASISString.capitalize_ascii modul ^ sufx) ::
+          (OASISString.uncapitalize_ascii modul ^ sufx) ::
           accu
         end
         sufx
@@ -6270,7 +6293,7 @@ module InternalInstallPlugin = struct
 end
 
 
-# 6273 "setup.ml"
+# 6296 "setup.ml"
 module OCamlbuildCommon = struct
 (* # 22 "src/plugins/ocamlbuild/OCamlbuildCommon.ml" *)
 
@@ -6648,7 +6671,7 @@ module OCamlbuildDocPlugin = struct
 end
 
 
-# 6651 "setup.ml"
+# 6674 "setup.ml"
 module CustomPlugin = struct
 (* # 22 "src/plugins/custom/CustomPlugin.ml" *)
 
@@ -6796,7 +6819,7 @@ module CustomPlugin = struct
 end
 
 
-# 6799 "setup.ml"
+# 6822 "setup.ml"
 open OASISTypes;;
 
 let setup_t =
@@ -6875,7 +6898,7 @@ let setup_t =
           alpha_features = ["ocamlbuild_more_args"];
           beta_features = [];
           name = "containers";
-          version = "0.17";
+          version = "0.18";
           license =
             OASISLicense.DEP5License
               (OASISLicense.DEP5Unit
@@ -6987,7 +7010,7 @@ let setup_t =
                    {
                       flag_description =
                         Some
-                          "Build advanced combinators, including CCLinq (requires \"sequence\")";
+                          "Build advanced combinators (requires \"sequence\")";
                       flag_default = [(OASISExpr.EBool true, true)]
                    });
                Library
@@ -7721,8 +7744,9 @@ let setup_t =
           plugin_data = []
        };
      oasis_fn = Some "_oasis";
-     oasis_version = "0.4.5";
-     oasis_digest = Some "\168\138o\130\169\030i2!\170\1730n\148\174\208";
+     oasis_version = "0.4.6";
+     oasis_digest =
+       Some "\006\139\194\135\189\021\197\018\208\031.\187\212'\016\192";
      oasis_exec = None;
      oasis_setup_args = [];
      setup_update = false
@@ -7730,6 +7754,6 @@ let setup_t =
 
 let setup () = BaseSetup.setup setup_t;;
 
-# 7734 "setup.ml"
+# 7758 "setup.ml"
 (* OASIS_STOP *)
 let () = setup ();;
diff --git a/src/advanced/CCLinq.mli b/src/advanced/CCLinq.mli
index 898eea54..02136979 100644
--- a/src/advanced/CCLinq.mli
+++ b/src/advanced/CCLinq.mli
@@ -33,7 +33,7 @@ Functions and operations are assumed to be referentially transparent, i.e.
 they should not rely on external side effects, they should not rely on
 the order of execution.
 
-@deprecated use {{: https://github.com/c-cube/olinq} OLinq} (once released)
+@deprecated use {{: https://github.com/c-cube/olinq} OLinq}
 
 {[
 
diff --git a/src/core/CCArray.ml b/src/core/CCArray.ml
index 848952a6..a7230a77 100644
--- a/src/core/CCArray.ml
+++ b/src/core/CCArray.ml
@@ -22,6 +22,10 @@ module type S = sig
 
   val get : 'a t -> int -> 'a
 
+  val get_safe : 'a t -> int -> 'a option
+  (** [get_safe a i] returns [Some a.(i)] if [i] is a valid index
+      @since 0.18 *)
+
   val set : 'a t -> int -> 'a -> unit
 
   val length : _ t -> int
@@ -291,6 +295,21 @@ let length = Array.length
 
 let get = Array.get
 
+let get_safe a i =
+  if i>=0 && i<Array.length a
+  then Some (Array.unsafe_get a i)
+  else None
+
+(*$=
+  (Some 1) (get_safe [|1;2;3|] 0)
+  (Some 2) (get_safe [|1;2;3|] 1)
+  (Some 3) (get_safe [|1;2;3|] 2)
+  None (get_safe [|1;2;3|] 4)
+  None (get_safe [|1;2;3|] max_int)
+  None (get_safe [|1;2;3|] ~-1)
+  None (get_safe [|1;2;3|] ~-42)
+*)
+
 let set = Array.set
 
 let fold = Array.fold_left
@@ -568,6 +587,24 @@ module Sub = struct
     if i<0 || j>=a.j then invalid_arg "Array.Sub.get";
     a.arr.(j)
 
+  let get_safe a i =
+    try Some (get a i)
+    with Invalid_argument _ -> None
+
+  (*$inject
+    let sub_a = Sub.make [|1;2;3;4;5|] 1 ~len:3
+  *)
+
+  (*$=
+    (Some 2) (Sub.get_safe sub_a 0)
+    (Some 3) (Sub.get_safe sub_a 1)
+    (Some 4) (Sub.get_safe sub_a 2)
+    None (Sub.get_safe sub_a 4)
+    None (Sub.get_safe sub_a max_int)
+    None (Sub.get_safe sub_a ~-1)
+    None (Sub.get_safe sub_a ~-42)
+  *)
+
   let set a i x =
     let j = a.i + i in
     if i<0 || j>=a.j then invalid_arg "Array.Sub.set";
diff --git a/src/core/CCArray.mli b/src/core/CCArray.mli
index 29157eb7..eb6b9d29 100644
--- a/src/core/CCArray.mli
+++ b/src/core/CCArray.mli
@@ -24,6 +24,10 @@ module type S = sig
 
   val get : 'a t -> int -> 'a
 
+  val get_safe : 'a t -> int -> 'a option
+  (** [get_safe a i] returns [Some a.(i)] if [i] is a valid index
+      @since 0.18 *)
+
   val set : 'a t -> int -> 'a -> unit
 
   val length : _ t -> int
diff --git a/src/core/CCFormat.mli b/src/core/CCFormat.mli
index 45d4aafb..7d2fd22b 100644
--- a/src/core/CCFormat.mli
+++ b/src/core/CCFormat.mli
@@ -37,6 +37,9 @@ val arrayi : ?start:string -> ?stop:string -> ?sep:string ->
 val seq : ?start:string -> ?stop:string -> ?sep:string -> 'a printer -> 'a sequence printer
 
 val opt : 'a printer -> 'a option printer
+(** [opt pp] prints options as follows:
+    [Some x] will become "some foo" if [pp x ---> "foo"]
+    [None] will become "none" *)
 
 (** In the tuple printers, the [sep] argument is only available
     @since 0.17 *)
diff --git a/src/core/CCFun.cppo.ml b/src/core/CCFun.cppo.ml
index c14cdb84..b8927c81 100644
--- a/src/core/CCFun.cppo.ml
+++ b/src/core/CCFun.cppo.ml
@@ -15,6 +15,16 @@ let (@@) f x = f x
 
 #endif
 
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 3
+
+let opaque_identity = Sys.opaque_identity
+
+#else
+
+let opaque_identity x = x
+
+#endif
+
 let compose f g x = g (f x)
 
 let compose_binop f g x y = g (f x) (f y)
diff --git a/src/core/CCFun.mli b/src/core/CCFun.mli
index 7d731708..8ff1f20d 100644
--- a/src/core/CCFun.mli
+++ b/src/core/CCFun.mli
@@ -65,6 +65,12 @@ val finally2 : h:(unit -> _) -> ('a -> 'b -> 'c) -> 'a -> 'b -> 'c
     [h ()] is called whether [f x y] rose an exception or not.
     @since 0.16 *)
 
+val opaque_identity : 'a -> 'a
+(** [opaque_identity x] is like [x], but prevents Flambda from using [x]'s
+    definition for optimizing it (flambda is an optimization/inlining pass
+    in OCaml >= 4.03).
+    @since 0.18 *)
+
 (** {2 Monad}
 
 Functions with a fixed domain are monads in their codomain *)
diff --git a/src/core/CCList.ml b/src/core/CCList.ml
index 857512ce..92c2747d 100644
--- a/src/core/CCList.ml
+++ b/src/core/CCList.ml
@@ -792,6 +792,38 @@ module Idx = struct
   *)
 end
 
+let range_by ~step i j =
+  let rec range i j acc =
+    if i=j then i::acc else range i (j-step) (j::acc)
+  in
+  if step = 0 then
+    raise (Invalid_argument "CCList.range_by")
+  else if (if step > 0 then i>j else i<j) then
+    []
+  else
+    range i ((j-i)/step*step + i)  []
+
+(* note: the last test checks that no error occurs due to overflows. *)
+(*$T
+  range_by ~step:1   0 0 = [0]
+  range_by ~step:1   5 0 = []
+  range_by ~step:2   1 0 = []
+  range_by ~step:2   0 4 = [0;2;4]
+  range_by ~step:2   0 5 = [0;2;4]
+  range_by ~step:~-1 0 0 = [0]
+  range_by ~step:~-1 0 5 = []
+  range_by ~step:~-2 0 1 = []
+  range_by ~step:~-2 5 1 = [5;3;1]
+  range_by ~step:~-2 5 0 = [5;3;1]
+  range_by ~step:max_int 0 2 = [0]
+*)
+
+(*$Q
+  Q.(pair small_int small_int) (fun (i,j) -> \
+    let i = min i j and j = max i j in \
+    range_by ~step:1 i j = range i j)
+*)
+
 let range i j =
   let rec up i j acc =
     if i=j then i::acc else up i (j-1) (j::acc)
diff --git a/src/core/CCList.mli b/src/core/CCList.mli
index 41f4e5d0..a3a35b26 100644
--- a/src/core/CCList.mli
+++ b/src/core/CCList.mli
@@ -275,6 +275,13 @@ end
 
 (** {2 Other Constructors} *)
 
+val range_by : step:int -> int -> int -> int t
+(** [range_by ~step i j] iterates on integers from [i] to [j] included,
+    where the difference between successive elements is [step].
+    use a negative [step] for a decreasing list.
+    @raise Invalid_argument if [step=0]
+    @since 0.18 *)
+
 val range : int -> int -> int t
 (** [range i j] iterates on integers from [i] to [j] included . It works
     both for decreasing and increasing ranges *)
diff --git a/src/core/CCOpt.ml b/src/core/CCOpt.ml
index b15d93d2..3413e18d 100644
--- a/src/core/CCOpt.ml
+++ b/src/core/CCOpt.ml
@@ -93,6 +93,10 @@ let get default x = match x with
   | None -> default
   | Some y -> y
 
+let get_or ~default x = match x with
+  | None -> default
+  | Some y -> y
+
 let get_exn = function
   | Some x -> x
   | None -> invalid_arg "CCOpt.get_exn"
diff --git a/src/core/CCOpt.mli b/src/core/CCOpt.mli
index feca2f3b..cb2242ba 100644
--- a/src/core/CCOpt.mli
+++ b/src/core/CCOpt.mli
@@ -27,7 +27,7 @@ val compare : ('a -> 'a -> int) -> 'a t -> 'a t -> int
 val equal : ('a -> 'a -> bool) -> 'a t -> 'a t -> bool
 
 val return : 'a -> 'a t
-(** Monadic return *)
+(** Monadic return, that is [return x = Some x] *)
 
 val (>|=) : 'a t -> ('a -> 'b) -> 'b t
 (** Infix version of {!map} *)
@@ -62,7 +62,13 @@ val for_all : ('a -> bool) -> 'a t -> bool
 
 val get : 'a -> 'a t -> 'a
 (** [get default x] unwraps [x], but if [x = None] it returns [default] instead.
-    @since 0.4.1 *)
+    @since 0.4.1
+    @deprecated use {!get_or} @since 0.18 *)
+
+val get_or : default:'a -> 'a t -> 'a
+(** [get_or ~default o] extracts the value from [o], or
+    returns [default] if [o = None].
+    @since 0.18 *)
 
 val get_exn : 'a t -> 'a
 (** Open the option, possibly failing if it is [None]
@@ -103,6 +109,7 @@ val (<+>) : 'a t -> 'a t -> 'a t
 
 val choice : 'a t list -> 'a t
 (** [choice] returns the first non-[None] element of the list, or [None] *)
+
 (** {2 Infix Operators}
     @since 0.16 *)
 
diff --git a/src/core/CCString.cppo.ml b/src/core/CCString.cppo.ml
index b476f92f..8a510d4e 100644
--- a/src/core/CCString.cppo.ml
+++ b/src/core/CCString.cppo.ml
@@ -639,6 +639,26 @@ let exists2 p s1 s2 =
   try iter2 (fun c1 c2 -> if p c1 c2 then raise MyExit) s1 s2; false
   with MyExit -> true
 
+(** {2 Ascii functions} *)
+
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 3
+
+let capitalize_ascii = String.capitalize_ascii
+let uncapitalize_ascii = String.uncapitalize_ascii
+let uppercase_ascii = String.uppercase_ascii
+let lowercase_ascii = String.lowercase_ascii
+
+#else
+
+let capitalize_ascii = String.capitalize
+let uncapitalize_ascii = String.uncapitalize
+let uppercase_ascii = String.uppercase
+let lowercase_ascii = String.lowercase
+
+#endif
+
+
+
 let pp buf s =
   Buffer.add_char buf '"';
   Buffer.add_string buf s;
diff --git a/src/core/CCString.mli b/src/core/CCString.mli
index a61d52fd..4d292fd1 100644
--- a/src/core/CCString.mli
+++ b/src/core/CCString.mli
@@ -378,6 +378,24 @@ val exists2 : (char -> char -> bool) -> string -> string -> bool
     @raise Invalid_argument if the strings have not the same length
     @since 0.12 *)
 
+(** {2 Ascii functions}
+
+    Those functions are deprecated in {!String} since 4.03, so we provide
+    a stable alias for them even in older versions *)
+
+val capitalize_ascii : string -> string
+(** See {!String}. @since 0.18 *)
+
+val uncapitalize_ascii : string -> string
+(** See {!String}. @since 0.18 *)
+
+val uppercase_ascii : string -> string
+(** See {!String}. @since 0.18 *)
+
+val lowercase_ascii : string -> string
+(** See {!String}. @since 0.18 *)
+
+
 (** {2 Splitting} *)
 
 module Split : sig
diff --git a/src/core/CCVector.ml b/src/core/CCVector.ml
index d1290cf5..40296609 100644
--- a/src/core/CCVector.ml
+++ b/src/core/CCVector.ml
@@ -243,12 +243,25 @@ let append_list a b = match b with
 *)
 
 let equal eq v1 v2 =
-  let n = min v1.size v2.size in
+  v1.size = v2.size
+  &&
+  let n = v1.size in
   let rec check i =
-    if i = n
-      then v1.size = v2.size
-      else eq (get v1 i) (get v2 i) && check (i+1)
-  in check 0
+    i = n || (eq (get v1 i) (get v2 i) && check (i+1))
+  in
+  check 0
+
+(*$T
+  equal (=) (create ()) (create ())
+  equal (=) (return 42) (return 42)
+  not (equal (=) (create ()) (return 42))
+  not (equal (=) (return 42) (create ()))
+*)
+
+(*$Q
+  Q.(let g = list_of_size Gen.(0--10) small_int in pair g g) (fun (l1,l2) -> \
+    equal (=) (of_list l1) (of_list l2) = (l1=l2))
+*)
 
 let compare cmp v1 v2 =
   let n = min v1.size v2.size in
diff --git a/src/core/META b/src/core/META
index 9f2ec31f..c5b3582c 100644
--- a/src/core/META
+++ b/src/core/META
@@ -1,6 +1,6 @@
 # OASIS_START
-# DO NOT EDIT (digest: 775c1a5da08322de06b23069a43379ed)
-version = "0.17"
+# DO NOT EDIT (digest: 048ee564ec86589b85b55f903119ad20)
+version = "0.18"
 description = "A modular standard library focused on data structures."
 requires = "bytes result"
 archive(byte) = "containers.cma"
@@ -9,7 +9,7 @@ archive(native) = "containers.cmxa"
 archive(native, plugin) = "containers.cmxs"
 exists_if = "containers.cma"
 package "unix" (
- version = "0.17"
+ version = "0.18"
  description = "A modular standard library focused on data structures."
  requires = "bytes unix"
  archive(byte) = "containers_unix.cma"
@@ -20,7 +20,7 @@ package "unix" (
 )
 
 package "top" (
- version = "0.17"
+ version = "0.18"
  description = "A modular standard library focused on data structures."
  requires =
  "compiler-libs.common containers containers.data containers.bigarray containers.string containers.unix containers.sexp containers.iter"
@@ -32,7 +32,7 @@ package "top" (
 )
 
 package "thread" (
- version = "0.17"
+ version = "0.18"
  description = "A modular standard library focused on data structures."
  requires = "containers threads"
  archive(byte) = "containers_thread.cma"
@@ -43,7 +43,7 @@ package "thread" (
 )
 
 package "string" (
- version = "0.17"
+ version = "0.18"
  description = "A modular standard library focused on data structures."
  requires = "bytes"
  archive(byte) = "containers_string.cma"
@@ -54,7 +54,7 @@ package "string" (
 )
 
 package "sexp" (
- version = "0.17"
+ version = "0.18"
  description = "A modular standard library focused on data structures."
  requires = "bytes"
  archive(byte) = "containers_sexp.cma"
@@ -65,7 +65,7 @@ package "sexp" (
 )
 
 package "iter" (
- version = "0.17"
+ version = "0.18"
  description = "A modular standard library focused on data structures."
  archive(byte) = "containers_iter.cma"
  archive(byte, plugin) = "containers_iter.cma"
@@ -75,7 +75,7 @@ package "iter" (
 )
 
 package "io" (
- version = "0.17"
+ version = "0.18"
  description = "A modular standard library focused on data structures."
  requires = "bytes"
  archive(byte) = "containers_io.cma"
@@ -86,7 +86,7 @@ package "io" (
 )
 
 package "data" (
- version = "0.17"
+ version = "0.18"
  description = "A modular standard library focused on data structures."
  requires = "bytes"
  archive(byte) = "containers_data.cma"
@@ -97,7 +97,7 @@ package "data" (
 )
 
 package "bigarray" (
- version = "0.17"
+ version = "0.18"
  description = "A modular standard library focused on data structures."
  requires = "containers bigarray bytes"
  archive(byte) = "containers_bigarray.cma"
@@ -108,7 +108,7 @@ package "bigarray" (
 )
 
 package "advanced" (
- version = "0.17"
+ version = "0.18"
  description = "A modular standard library focused on data structures."
  requires = "containers sequence"
  archive(byte) = "containers_advanced.cma"
diff --git a/src/data/CCGraph.ml b/src/data/CCGraph.ml
index 37a9da15..2155f089 100644
--- a/src/data/CCGraph.ml
+++ b/src/data/CCGraph.ml
@@ -43,6 +43,10 @@ module Seq = struct
     a (fun x -> acc := f !acc x);
     !acc
   let to_list seq = fold (fun acc x->x::acc) [] seq |> List.rev
+  exception Exit_
+  let exists_ f seq =
+    try seq (fun x -> if f x then raise Exit_); false
+    with Exit_ -> true
 end
 
 (** {2 Interfaces for graphs} *)
@@ -315,6 +319,15 @@ module Traverse = struct
   end
 end
 
+(** {2 Cycles} *)
+
+let is_dag ?(tbl=mk_table 128) ~graph vs =
+  Traverse.Event.dfs ~tbl ~graph vs
+  |> Seq.exists_
+    (function
+      | `Edge (_, `Back) -> true
+      | _ -> false)
+
 (** {2 Topological Sort} *)
 
 exception Has_cycle
diff --git a/src/data/CCGraph.mli b/src/data/CCGraph.mli
index 22bc1233..5ccb00f2 100644
--- a/src/data/CCGraph.mli
+++ b/src/data/CCGraph.mli
@@ -224,6 +224,17 @@ module Traverse : sig
   end
 end
 
+(** {2 Cycles} *)
+
+val is_dag :
+  ?tbl:'v set ->
+  graph:('v, _) t ->
+  'v sequence ->
+  bool
+(** [is_dag ~graph vs] returns [true] if the subset of [graph] reachable
+    from [vs] is acyclic.
+    @since 0.18 *)
+
 (** {2 Topological Sort} *)
 
 exception Has_cycle
diff --git a/src/data/CCTrie.ml b/src/data/CCTrie.ml
index 7af7a165..569b6bdc 100644
--- a/src/data/CCTrie.ml
+++ b/src/data/CCTrie.ml
@@ -368,7 +368,7 @@ module Make(W : WORD)
   *)
 
   (*$Q
-    Q.(pair (list (pair printable_string int)) printable_string) (fun (l,s) -> \
+    Q.(pair (list (pair (printable_string_of_size Gen.(0 -- 30)) int)) printable_string) (fun (l,s) -> \
       let m = String.of_list l in \
       let s' = String.longest_prefix s m in \
       CCString.prefix ~pre:s' s)
diff --git a/src/iter/CCLazy_list.ml b/src/iter/CCLazy_list.ml
index ffaf76ce..a258f372 100644
--- a/src/iter/CCLazy_list.ml
+++ b/src/iter/CCLazy_list.ml
@@ -40,6 +40,27 @@ let rec map ~f l =
     | lazy (Cons (x,tl)) -> Cons (f x, map ~f tl)
   )
 
+let filter ~f l =
+  let rec aux f l = match l with
+    | lazy Nil -> Nil
+    | lazy (Cons (x,tl)) when f x -> Cons (x, lazy (aux f tl))
+    | lazy (Cons (_, tl)) ->  aux f tl
+  in
+  lazy (aux f l)
+
+(*$=
+  [2;4;6] (of_list [1;2;3;4;5;6;7] |> filter ~f:(fun x -> x mod 2=0) |> to_list)
+  [2;4;6] (of_gen Gen.(1 -- max_int) |> filter ~f:(fun x -> x mod 2=0) |> take 3 |> to_list)
+*)
+
+let rec take n l =
+  lazy (
+    match l with
+      | _ when n=0 -> Nil
+      | lazy Nil -> Nil
+      | lazy (Cons (x,tl)) -> Cons (x, take (n-1) tl)
+  )
+
 let rec append a b =
   lazy (
     match a with
diff --git a/src/iter/CCLazy_list.mli b/src/iter/CCLazy_list.mli
index 6a51cd3b..3f046fb2 100644
--- a/src/iter/CCLazy_list.mli
+++ b/src/iter/CCLazy_list.mli
@@ -31,6 +31,14 @@ val head : 'a t -> ('a * 'a t) option
 val map : f:('a -> 'b) -> 'a t -> 'b t
 (** Lazy map *)
 
+val filter : f:('a -> bool) -> 'a t -> 'a t
+(** Filter values.
+    @since 0.18 *)
+
+val take : int -> 'a t -> 'a t
+(** Take at most n values.
+    @since 0.18 *)
+
 val append : 'a t -> 'a t -> 'a t
 (** Lazy concatenation *)