From 113ea6d395289c8b5ad8d4f443836125e8ccbb8d Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Sat, 17 May 2014 01:00:00 +0200
Subject: [PATCH] updated and fixed things in core/: fixed warnings, updated
 Sequence/Gen with tests and more recent interface; added printers

---
 core/CCGen.ml           | 466 ++++++++++++++++++++++++++++++++--------
 core/CCGen.mli          |  17 +-
 core/CCList.ml          |  17 +-
 core/CCList.mli         |   4 +
 core/CCSequence.ml      | 276 +++++++++++-------------
 core/CCSequence.mli     |  88 ++++----
 core/CCVector.ml        |   3 -
 core/CCVector.mli       |  68 +++---
 misc/lazyGraph.ml       |   6 +-
 misc/persistentGraph.ml |   6 +-
 tests/benchs.ml         |   2 +-
 11 files changed, 613 insertions(+), 340 deletions(-)

diff --git a/core/CCGen.ml b/core/CCGen.ml
index fa5e5378..a2db99d7 100644
--- a/core/CCGen.ml
+++ b/core/CCGen.ml
@@ -67,10 +67,6 @@ module type S = sig
   val fold : ('b -> 'a -> 'b) -> 'b -> 'a t -> 'b
     (** Fold on the generator, tail-recursively *)
 
-  val fold2 : ('c -> 'a -> 'b -> 'c) -> 'c -> 'a t -> 'b t -> 'c
-    (** Fold on the two enums in parallel. Stops once one of the enums
-        is exhausted. *)
-
   val reduce : ('a -> 'a -> 'a) -> 'a t -> 'a
     (** Fold on non-empty sequences (otherwise raise Invalid_argument) *)
 
@@ -83,9 +79,6 @@ module type S = sig
   val iteri : (int -> 'a -> unit) -> 'a t -> unit
     (** Iterate on elements with their index in the enum, from 0 *)
 
-  val iter2 : ('a -> 'b -> unit) -> 'a t -> 'b t -> unit
-    (** Iterate on the two sequences. Stops once one of them is exhausted.*)
-
   val length : _ t -> int
     (** Length of an enum (linear time) *)
 
@@ -100,7 +93,7 @@ module type S = sig
   val flatten : 'a gen t -> 'a t
     (** Flatten the enumeration of generators *)
 
-  val flatMap : ('a -> 'b gen) -> 'a t -> 'b t
+  val flat_map : ('a -> 'b gen) -> 'a t -> 'b t
     (** Monadic bind; each element is transformed to a sub-enum
         which is then iterated on, before the next element is processed,
         and so on. *)
@@ -118,19 +111,24 @@ module type S = sig
     (** n-th element, or Not_found
         @raise Not_found if the generator contains less than [n] arguments *)
 
+  val take_nth : int -> 'a t -> 'a t
+    (** [take_nth n g] returns every element of [g] whose index
+        is a multiple of [n]. For instance [take_nth 2 (1--10) |> to_list]
+        will return [1;3;5;7;9] *)
+
   val filter : ('a -> bool) -> 'a t -> 'a t
     (** Filter out elements that do not satisfy the predicate.  *)
 
-  val takeWhile : ('a -> bool) -> 'a t -> 'a t
+  val take_while : ('a -> bool) -> 'a t -> 'a t
     (** Take elements while they satisfy the predicate *)
 
-  val dropWhile : ('a -> bool) -> 'a t -> 'a t
+  val drop_while : ('a -> bool) -> 'a t -> 'a t
     (** Drop elements while they satisfy the predicate *)
 
-  val filterMap : ('a -> 'b option) -> 'a t -> 'b t
-    (** Maps some elements to 'b, drop the other ones *)
+  val filter_map : ('a -> 'b option) -> 'a t -> 'b t
+    (** _maps some elements to 'b, drop the other ones *)
 
-  val zipIndex : 'a t -> (int * 'a) t
+  val zip_index : 'a t -> (int * 'a) t
     (** Zip elements with their index in the enum *)
 
   val unzip : ('a * 'b) t -> 'a t * 'b t
@@ -174,10 +172,13 @@ module type S = sig
   (** {2 Multiple iterators} *)
 
   val map2 : ('a -> 'b -> 'c) -> 'a t -> 'b t -> 'c t
+    (** map on the two sequences. Stops once one of them is exhausted.*)
 
   val iter2 : ('a -> 'b -> unit) -> 'a t -> 'b t -> unit
+    (** Iterate on the two sequences. Stops once one of them is exhausted.*)
 
   val fold2 : ('acc -> 'a -> 'b -> 'acc) -> 'acc -> 'a t -> 'b t -> 'acc
+    (** Fold the common prefix of the two iterators *)
 
   val for_all2 : ('a -> 'b -> bool) -> 'a t -> 'b t -> bool
     (** Succeeds if all pairs of elements satisfy the predicate.
@@ -187,7 +188,7 @@ module type S = sig
     (** Succeeds if some pair of elements satisfy the predicate.
         Ignores elements of an iterator if the other runs dry. *)
 
-  val zipWith : ('a -> 'b -> 'c) -> 'a t -> 'b t -> 'c t
+  val zip_with : ('a -> 'b -> 'c) -> 'a t -> 'b t -> 'c t
     (** Combine common part of the enums (stops when one is exhausted) *)
 
   val zip : 'a t -> 'b t -> ('a * 'b) t
@@ -312,15 +313,33 @@ end
 
 let empty () = None
 
+(*$T empty
+  empty |> to_list = []
+*)
+
 let singleton x =
   let first = ref true in
   fun () ->
     if !first then (first := false; Some x) else None
 
-let rec repeat x () = Some x
+(*T singleton
+  singleton 1 |> to_list = [1]
+  singleton "foo" |> to_list = ["foo"]
+*)
+
+let repeat x () = Some x
+
+(*$T repeat
+  repeat 42 |> take 3 |> to_list = [42; 42; 42]
+*)
 
 let repeatedly f () = Some (f ())
 
+(*$T repeatedly
+  repeatedly (let r = ref 0 in fun () -> incr r; !r) \
+    |> take 5 |> to_list = [1;2;3;4;5]
+*)
+
 let iterate x f =
   let cur = ref x in
   fun () ->
@@ -328,6 +347,10 @@ let iterate x f =
     cur := f !cur;
     Some x
 
+(*$T iterate
+  iterate 0 ((+)1) |> take 5 |> to_list = [0;1;2;3;4]
+*)
+
 let next gen = gen ()
 
 let get gen = gen ()
@@ -337,6 +360,14 @@ let get_exn gen =
   | Some x -> x
   | None -> raise (Invalid_argument "Gen.get_exn")
 
+(*$R get_exn
+  let g = of_list [1;2;3] in
+  assert_equal 1 (get_exn g);
+  assert_equal 2 (get_exn g);
+  assert_equal 3 (get_exn g);
+  assert_raises (Invalid_argument "Gen.get_exn") (fun () -> get_exn g)
+*)
+
 let junk gen = ignore (gen ())
 
 let rec fold f acc gen =
@@ -344,6 +375,11 @@ let rec fold f acc gen =
   | None -> acc
   | Some x -> fold f (f acc x) gen
 
+(*$Q
+  (Q.list Q.small_int) (fun l -> \
+    of_list l |> fold (fun l x->x::l) [] = List.rev l)
+*)
+
 let reduce f g =
   let acc = match g () with
     | None -> raise (Invalid_argument "reduce")
@@ -361,6 +397,11 @@ let unfold f acc =
       acc := acc';
       Some x
 
+(*$T unfold
+  unfold (fun (prev,cur) -> Some (prev, (cur,prev+cur))) (0,1) \
+    |> take 7 |> to_list = [0; 1; 1; 2; 3; 5; 8]
+*)
+
 let init ?(limit=max_int) f =
   let r = ref 0 in
   fun () ->
@@ -371,6 +412,10 @@ let init ?(limit=max_int) f =
       let _ = incr r in
       Some x
 
+(*$T init
+  init ~limit:5 (fun i->i) |> to_list = [0;1;2;3;4]
+*)
+
 let rec iter f gen =
   match gen() with
   | None -> ()
@@ -387,9 +432,19 @@ let is_empty gen = match gen () with
   | None -> true
   | Some _ -> false
 
+(*$T
+  is_empty empty
+  not (is_empty (singleton 2))
+*)
+
 let length gen =
   fold (fun acc _ -> acc + 1) 0 gen
 
+(*$Q
+  (Q.list Q.small_int) (fun l -> \
+    of_list l |> length = List.length l)
+*)
+
 (* useful state *)
 type 'a run_state =
   | Init
@@ -412,10 +467,10 @@ let scan f acc g =
             state := Run acc';
             Some acc'
 
-let rec iter2 f gen1 gen2 =
-  match gen1(), gen2() with
-  | Some x, Some y -> f x y; iter2 f gen1 gen2
-  | _ -> ()
+(*$T scan
+  scan (fun acc x -> x+1::acc) [] (1--5) |> to_list \
+    = [[]; [2]; [3;2]; [4;3;2]; [5;4;3;2]; [6;5;4;3;2]]
+*)
 
 (** {3 Lazy} *)
 
@@ -427,6 +482,12 @@ let map f gen =
     | None -> stop:= true; None
     | Some x -> Some (f x)
 
+(*$Q map
+  (Q.list Q.small_int) (fun l -> \
+    let f x = x*2 in \
+    of_list l |> map f |> to_list = List.map f l)
+*)
+
 let append gen1 gen2 =
   let first = ref true in
   let rec next() =
@@ -437,6 +498,11 @@ let append gen1 gen2 =
     else gen2()
   in next
 
+(*$Q
+  (Q.pair (Q.list Q.small_int)(Q.list Q.small_int)) (fun (l1,l2) -> \
+    append (of_list l1) (of_list l2) |> to_list = l1 @ l2)
+*)
+
 let flatten next_gen =
   let state = ref Init in
   (* get next element *)
@@ -455,7 +521,7 @@ let flatten next_gen =
   in
   next
 
-let flatMap f next_elem =
+let flat_map f next_elem =
   let state = ref Init in
   let rec next() =
     match !state with
@@ -474,6 +540,12 @@ let flatMap f next_elem =
   in
   next
 
+(*$Q flat_map
+  (Q.list Q.small_int) (fun l -> \
+    let f x = of_list [x;x*2] in \
+    eq (map f (of_list l) |> flatten) (flat_map f (of_list l)))
+*)
+
 let mem ?(eq=(=)) x gen =
   let rec mem eq x gen =
     match gen() with
@@ -491,6 +563,11 @@ let take n gen =
       | None -> count := ~-1; None   (* indicate stop *)
       | (Some _) as x -> incr count; x
 
+(*$Q
+  (Q.pair Q.small_int (Q.list Q.small_int)) (fun (n,l) -> \
+    of_list l |> take n |> length = Pervasives.min n (List.length l))
+*)
+
 (* call [gen] at most [n] times, and stop *)
 let rec __drop n gen =
   if n = 0 then ()
@@ -511,6 +588,12 @@ let drop n gen =
         gen()
       end
 
+(*$Q
+  (Q.pair Q.small_int (Q.list Q.small_int)) (fun (n,l) -> \
+    let g1,g2 = take n (of_list l), drop n (of_list l) in \
+    append g1 g2 |> to_list = l)
+*)
+
 let nth n gen =
   assert (n>=0);
   __drop n gen;
@@ -518,6 +601,25 @@ let nth n gen =
   | None -> raise Not_found
   | Some x -> x
 
+(*$= nth & ~printer:string_of_int
+  4 (nth 4 (0--10))
+  8 (nth 8 (0--10))
+*)
+
+(*$T
+  (try ignore (nth 11 (1--10)); false with Not_found -> true)
+*)
+
+let take_nth n gen =
+  assert (n>=1);
+  let i = ref n in
+  let rec next() =
+    match gen() with
+    | None -> None
+    | (Some _) as res when !i = n -> i:=1; res
+    | Some _ -> incr i; next()
+  in next
+
 let filter p gen =
   let rec next () =
     (* wrap exception into option, for next to be tailrec *)
@@ -529,16 +631,23 @@ let filter p gen =
         else next ()  (* discard element *)
   in next
 
-let takeWhile p gen =
+(*$T
+  filter (fun x ->x mod 2 = 0) (1--10) |> to_list = [2;4;6;8;10]
+*)
+
+let take_while p gen =
   let stop = ref false in
-  let rec next () =
+  fun () ->
     if !stop
     then None
     else match gen() with
     | (Some x) as res ->
         if p x then res else (stop := true; None)
     | None -> stop:=true; None
-  in next
+
+(*$T
+  take_while (fun x ->x<10) (1--1000) |> eq (1--9)
+*)
 
 module DropWhileState = struct
   type t =
@@ -547,9 +656,9 @@ module DropWhileState = struct
     | Yield
 end
 
-let dropWhile p gen =
+let drop_while p gen =
   let open DropWhileState in
-  let state = ref Stop in
+  let state = ref Drop in
   let rec next () =
     match !state with
     | Stop -> None
@@ -566,7 +675,11 @@ let dropWhile p gen =
         end
   in next
 
-let filterMap f gen =
+(*$T
+  drop_while (fun x-> x<10) (1--20) |> eq (10--20)
+*)
+
+let filter_map f gen =
   (* tailrec *)
   let rec next () =
     match gen() with
@@ -577,7 +690,12 @@ let filterMap f gen =
         | (Some _) as res -> res
   in next
 
-let zipIndex gen =
+(*$T
+  filter_map (fun x-> if x mod 2 = 0 then Some (string_of_int x) else None) (1--10) \
+    |> to_list = List.map string_of_int [2;4;6;8;10]
+*)
+
+let zip_index gen =
   let r = ref ~-1 in
   fun () ->
     match gen() with
@@ -586,6 +704,10 @@ let zipIndex gen =
         incr r;
         Some (!r, x)
 
+(*$T
+  zip_index (1--5) |> to_list = [0,1; 1,2; 2,3; 3,4; 4,5]
+*)
+
 let unzip gen =
   let stop = ref false in
   let q1 = Queue.create () in
@@ -612,6 +734,17 @@ let unzip gen =
   in
   next_left, next_right
 
+(*$T
+  unzip (of_list [1,2;3,4]) |> (fun (x,y)-> to_list x, to_list y) \
+    = ([1;3], [2;4])
+*)
+
+(*$Q
+  (Q.list (Q.pair Q.small_int Q.small_int)) (fun l -> \
+    of_list l |> unzip |> (fun (x,y) -> to_list x,to_list y) = \
+    List.split l)
+*)
+
 (* [partition p l] returns the elements that satisfy [p],
    and the elements that do not satisfy [p] *)
 let partition p gen =
@@ -637,6 +770,11 @@ let partition p gen =
   in
   nexttrue, nextfalse
 
+(*$T
+  partition (fun x -> x mod 2 = 0) (1--10) |> \
+    (fun (x,y)->to_list x, to_list y) = ([2;4;6;8;10], [1;3;5;7;9])
+*)
+
 let rec for_all p gen =
   match gen() with
   | None -> true
@@ -654,6 +792,11 @@ let min ?(lt=fun x y -> x < y) gen =
   in
   fold (fun min x -> if lt x min then x else min) first gen
 
+(*$T
+  min (of_list [1;4;6;0;11; -2]) = ~-2
+  (try ignore (min empty); false with Invalid_argument _ -> true)
+*)
+
 let max ?(lt=fun x y -> x < y) gen =
   let first = match gen () with
     | Some x -> x
@@ -661,6 +804,11 @@ let max ?(lt=fun x y -> x < y) gen =
   in
   fold (fun max x -> if lt max x then x else max) first gen
 
+(*$T
+  max (of_list [1;4;6;0;11; -2]) = 11
+  (try ignore (max empty); false with Invalid_argument _ -> true)
+*)
+
 let eq ?(eq=(=)) gen1 gen2 =
   let rec check () =
     match gen1(), gen2() with
@@ -670,6 +818,11 @@ let eq ?(eq=(=)) gen1 gen2 =
   in
   check ()
 
+(*$Q
+  (Q.pair (Q.list Q.small_int)(Q.list Q.small_int)) (fun (l1,l2) -> \
+    eq (of_list l1)(of_list l2) = (l1 = l2))
+*)
+
 let lexico ?(cmp=Pervasives.compare) gen1 gen2 =
   let rec lexico () =
     match gen1(), gen2() with
@@ -683,17 +836,32 @@ let lexico ?(cmp=Pervasives.compare) gen1 gen2 =
 
 let compare ?cmp gen1 gen2 = lexico ?cmp gen1 gen2
 
+(*$Q
+  (Q.pair (Q.list Q.small_int)(Q.list Q.small_int)) (fun (l1,l2) -> \
+    let sign x = if x < 0 then -1 else if x=0 then 0 else 1 in \
+    sign (compare (of_list l1)(of_list l2)) = sign (Pervasives.compare l1 l2))
+*)
+
 let rec find p e = match e () with
   | None -> None
   | Some x when p x -> Some x
   | Some _ -> find p e
 
+(*$T
+   find (fun x -> x>=5) (1--10) = Some 5
+   find (fun x -> x>5) (1--4) = None
+*)
+
 let sum e =
   let rec sum acc = match e() with
   | None -> acc
   | Some x -> sum (x+acc)
   in sum 0
 
+(*$T
+  sum (1--10) = 55
+*)
+
 (** {2 Multiple Iterators} *)
 
 let map2 f e1 e2 =
@@ -701,11 +869,20 @@ let map2 f e1 e2 =
   | Some x, Some y -> Some (f x y)
   | _ -> None
 
+(*$T
+  map2 (+) (1--5) (1--4) |> eq (of_list [2;4;6;8])
+  map2 (+) (1--5) (repeat 0) |> eq (1--5)
+*)
+
 let rec iter2 f e1 e2 =
   match e1(), e2() with
   | Some x, Some y -> f x y; iter2 f e1 e2
   | _ -> ()
 
+(*$T iter2
+  let r = ref 0 in iter2 (fun _ _ -> incr r) (1--10) (4--6); !r = 3
+*)
+
 let rec fold2 f acc e1 e2 =
   match e1(), e2() with
   | Some x, Some y -> fold2 f (f acc x y) e1 e2
@@ -721,7 +898,7 @@ let rec exists2 p e1 e2 =
   | Some x, Some y -> p x y || exists2 p e1 e2
   | _ -> false
 
-let zipWith f a b =
+let zip_with f a b =
   let stop = ref false in
   fun () ->
     if !stop then None
@@ -729,7 +906,13 @@ let zipWith f a b =
     | Some xa, Some xb -> Some (f xa xb)
     | _ -> stop:=true; None
 
-let zip a b = zipWith (fun x y -> x,y) a b
+let zip a b = zip_with (fun x y -> x,y) a b
+
+(*$Q
+  (Q.list Q.small_int) (fun l -> \
+    zip_with (fun x y->x,y) (of_list l) (of_list l) \
+      |> unzip |> fst |> to_list = l)
+*)
 
 (** {3 Complex combinators} *)
 
@@ -746,7 +929,6 @@ module MergeState = struct
     | Stop
 end
 
-(* TODO tests *)
 (* state machine:
     (NewGen -> YieldAndNew)* // then no more generators in next_gen, so
     -> Yield* -> Stop *)
@@ -792,6 +974,11 @@ let merge next_gen =
           end
   in next
 
+(*$T
+  merge (of_list [of_list [1;3;5]; of_list [2;4;6]; of_list [7;8;9]]) \
+    |> to_list |> List.sort Pervasives.compare = [1;2;3;4;5;6;7;8;9]
+*)
+
 let intersection ?(cmp=Pervasives.compare) gen1 gen2 =
   let x1 = ref (gen1 ()) in
   let x2 = ref (gen2 ()) in
@@ -808,6 +995,11 @@ let intersection ?(cmp=Pervasives.compare) gen1 gen2 =
     | _ -> None
   in next
 
+(*$T
+  intersection (of_list [1;1;2;3;4;8]) (of_list [1;2;4;5;6;7;8;9]) \
+    |> to_list = [1;2;4;8]
+*)
+
 let sorted_merge ?(cmp=Pervasives.compare) gen1 gen2 =
   let x1 = ref (gen1 ()) in
   let x2 = ref (gen2 ()) in
@@ -825,6 +1017,11 @@ let sorted_merge ?(cmp=Pervasives.compare) gen1 gen2 =
       x2 := gen2 ();
       r
 
+(*$T
+  sorted_merge (of_list [1;2;2;3;5;10;100]) (of_list [2;4;5;6;11]) \
+    |> to_list = [1;2;2;2;3;4;5;5;6;10;11;100]
+*)
+
 (** {4 Mutable heap (taken from heap.ml to avoid dependencies)} *)
 module Heap = struct
   type 'a t = {
@@ -884,6 +1081,11 @@ let sorted_merge_n ?(cmp=Pervasives.compare) l =
       | None -> Some x (* gen empty, drop it *)
     end
 
+(*$T
+  sorted_merge_n [of_list [1;2;2;3;5;10;100]; of_list [2;4;5;6;11]; (6--10)] \
+    |> to_list = [1;2;2;2;3;4;5;5;6;6;7;8;9;10;10;11;100]
+*)
+
 let round_robin ?(n=2) gen =
   (* array of queues, together with their index *)
   let qs = Array.init n (fun i -> Queue.create ()) in
@@ -916,6 +1118,11 @@ let round_robin ?(n=2) gen =
   let l = Array.mapi (fun i _ -> (fun () -> next i)) qs in
   Array.to_list l
 
+(*$T
+  round_robin ~n:3 (1--12) |> List.map to_list = \
+    [[1;4;7;10]; [2;5;8;11]; [3;6;9;12]]
+*)
+
 (* Duplicate the enum into [n] generators (default 2). The generators
    share the same underlying instance of the enum, so the optimal case is
    when they are consumed evenly *)
@@ -943,6 +1150,12 @@ let tee ?(n=2) gen =
   let l = Array.mapi (fun i _ -> (fun () -> next i)) qs in
   Array.to_list l
 
+(*$T
+  tee ~n:3 (1--12) |> List.map to_list = \
+    [to_list (1--12); to_list (1--12); to_list (1--12)]
+*)
+
+
 module InterleaveState = struct
   type 'a t =
     | Only of 'a gen 
@@ -971,6 +1184,11 @@ let interleave gen_a gen_b =
           res
   in next
 
+(*$T
+  interleave (repeat 0) (1--5) |> take 10 |> to_list = \
+    [0;1;0;2;0;3;0;4;0;5]
+*)
+
 module IntersperseState = struct
   type 'a t =
     | Start
@@ -1000,6 +1218,10 @@ let intersperse x gen =
         | Some _ as res -> state := YieldElem res; next()
   in next
 
+(*$T
+  intersperse 0 (1--5) |> to_list = [1;0;2;0;3;0;4;0;5]
+*)
+
 (* Cartesian product *)
 let product gena genb =
   let all_a = ref [] in
@@ -1040,6 +1262,12 @@ let product gena genb =
   in
   next
 
+(*$T
+  product (1--3) (of_list ["a"; "b"]) |> to_list \
+    |> List.sort Pervasives.compare = \
+      [1, "a"; 1, "b"; 2, "a"; 2, "b"; 3, "a"; 3, "b"]
+*)
+
 (* Group equal consecutive elements together. *)
 let group ?(eq=(=)) gen =
   match gen() with
@@ -1062,6 +1290,11 @@ let group ?(eq=(=)) gen =
         Some l
     in next
 
+(*$T
+  group (of_list [0;0;0;1;0;2;2;3;4;5;5;5;5;10]) |> to_list = \
+    [[0;0;0];[1];[0];[2;2];[3];[4];[5;5;5;5];[10]]
+*)
+
 let uniq ?(eq=(=)) gen =
   let state = ref Init in
   let rec next() = match !state with
@@ -1081,6 +1314,11 @@ let uniq ?(eq=(=)) gen =
         end
   in next
 
+(*$T
+  uniq (of_list [0;0;0;1;0;2;2;3;4;5;5;5;5;10]) |> to_list = \
+    [0;1;0;2;3;4;5;10]
+*)
+
 let sort ?(cmp=Pervasives.compare) gen =
   (* build heap *)
   let h = Heap.empty ~cmp in
@@ -1089,22 +1327,32 @@ let sort ?(cmp=Pervasives.compare) gen =
     if Heap.is_empty h
       then None
       else Some (Heap.pop h)
+(*$T
+  sort (of_list [0;0;0;1;0;2;2;3;4;5;5;5;-42;5;10]) |> to_list = \
+    [-42;0;0;0;0;1;2;2;3;4;5;5;5;5;10]
+*)
+
 
 (* NOTE: using a set is not really possible, because once we have built the
   set there is no simple way to iterate on it *)
 let sort_uniq ?(cmp=Pervasives.compare) gen =
   uniq ~eq:(fun x y -> cmp x y = 0) (sort ~cmp gen)
 
+(*$T
+  sort_uniq (of_list [0;0;0;1;0;2;2;3;4;5;42;5;5;42;5;10]) |> to_list = \
+    [0;1;2;3;4;5;10;42]
+*)
+
 let chunks n e =
   let rec next () =
     match e() with
     | None -> None
     | Some x ->
         let a = Array.make n x in
-        fill a (n-1)
+        fill a 1
 
   and fill a i =
-    (* fill the array. [i] elements remain to fill *)
+    (* fill the array. [i]: current index to fill *)
     if i = n
     then Some a
     else match e() with
@@ -1115,6 +1363,11 @@ let chunks n e =
   in
   next
 
+(*$T
+  chunks 25 (0--100) |> map Array.to_list |> to_list = \
+    List.map to_list [(0--24); (25--49);(50--74);(75--99);(100--100)]
+*)
+
 (*
 let permutations enum =
   failwith "not implemented" (* TODO *)
@@ -1139,19 +1392,27 @@ let of_list l =
 let to_rev_list gen =
   fold (fun acc x -> x :: acc) [] gen
 
+(*$Q
+  (Q.list Q.small_int) (fun l -> \
+    to_rev_list (of_list l) = List.rev l)
+*)
+
 let to_list gen = List.rev (to_rev_list gen)
 
 let to_array gen =
   let l = to_rev_list gen in
-  let a = Array.of_list l in
-  let n = Array.length a in
-  (* reverse array *)
-  for i = 0 to (n-1) / 2 do
-    let tmp = a.(i) in
-    a.(i) <- a.(n-i-1);
-    a.(n-i-1) <- tmp
-  done;
-  a
+  match l with
+  | [] -> [| |]
+  | _ ->
+    let a = Array.of_list l in
+    let n = Array.length a in
+    (* reverse array *)
+    for i = 0 to (n-1) / 2 do
+      let tmp = a.(i) in
+      a.(i) <- a.(n-i-1);
+      a.(n-i-1) <- tmp
+    done;
+    a
 
 let of_array ?(start=0) ?len a =
   let len = match len with
@@ -1163,6 +1424,11 @@ let of_array ?(start=0) ?len a =
       then None
       else (let x = a.(!i) in incr i; Some x)
 
+(*$Q
+  (Q.array Q.small_int) (fun a -> \
+    of_array a |> to_array = a)
+*)
+
 let rand_int i =
   repeatedly (fun () -> Random.int i)
 
@@ -1200,7 +1466,7 @@ let pp ?(start="") ?(stop="") ?(sep=",") ?(horizontal=false) pp_elem formatter g
 module Infix = struct
   let (--) = int_range
 
-  let (>>=) x f = flatMap f x
+  let (>>=) x f = flat_map f x
 end
 
 include Infix
@@ -1221,8 +1487,6 @@ module Restart = struct
 
   let repeat x () = repeat x
 
-  let repeatedly f () = repeatedly f
-
   let unfold f acc () = unfold f acc 
 
   let init ?limit f () = init ?limit f
@@ -1257,7 +1521,7 @@ module Restart = struct
 
   let flatten e () = flatten (e ())
 
-  let flatMap f e () = flatMap f (e ())
+  let flat_map f e () = flat_map f (e ())
 
   let mem ?eq x e = mem ?eq x (e ())
 
@@ -1267,19 +1531,21 @@ module Restart = struct
 
   let nth n e = nth n (e ())
 
+  let take_nth n e () = take_nth n (e ())
+
   let filter p e () = filter p (e ())
 
-  let takeWhile p e () = takeWhile p (e ())
+  let take_while p e () = take_while p (e ())
 
-  let dropWhile p e () = dropWhile p (e ())
+  let drop_while p e () = drop_while p (e ())
 
-  let filterMap f e () = filterMap f (e ())
+  let filter_map f e () = filter_map f (e ())
 
-  let zipWith f e1 e2 () = zipWith f (e1 ()) (e2 ())
+  let zip_with f e1 e2 () = zip_with f (e1 ()) (e2 ())
 
   let zip e1 e2 () = zip (e1 ()) (e2 ())
 
-  let zipIndex e () = zipIndex (e ())
+  let zip_index e () = zip_index (e ())
 
   let unzip e = map fst e, map snd e
 
@@ -1373,7 +1639,7 @@ module Restart = struct
   module Infix = struct
     let (--) = int_range
 
-    let (>>=) x f = flatMap f x
+    let (>>=) x f = flat_map f x
   end
 
   include Infix
@@ -1386,53 +1652,65 @@ end
 
 let start g = g ()
 
-(** {4 Mutable double-linked list, similar to {! Deque.t} *)
+(** {6 Unrolled mutable list} *)
 module MList = struct
-  type 'a t = 'a node option ref
-  and 'a node = {
-    content : 'a;
-    mutable prev : 'a node;
-    mutable next : 'a node;
-  }
+  type 'a node =
+    | Nil
+    | Cons of 'a array * int ref * 'a node ref
 
-  let create () = ref None
+  let of_gen gen =
+    let start = ref Nil in
+    let chunk_size = ref 8 in
+    (* fill the list. prev: tail-reference from previous node,
+     * cur: current list node *)
+    let rec fill prev cur =
+      match cur, gen() with
+      | _, None -> prev := cur; ()  (* done *)
+      | Nil, Some x ->
+          let n = !chunk_size in
+          if n < 4096 then chunk_size := 2 * !chunk_size;
+          fill prev (Cons (Array.make n x, ref 1, ref Nil))
+      | Cons (a, n, next), Some x ->
+          assert (!n < Array.length a);
+          a.(!n) <- x;
+          incr n;
+          if !n = Array.length a
+          then begin
+            prev := cur;
+            fill next Nil
+          end else fill prev cur 
+    in
+    fill start !start ;
+    !start
 
-  let is_empty d =
-    match !d with
-    | None -> true
-    | Some _ -> false
-
-  let push_back d x =
-    match !d with
-    | None ->
-      let rec elt = {
-        content = x; prev = elt; next = elt; } in
-      d := Some elt
-    | Some first ->
-      let elt = { content = x; next=first; prev=first.prev; } in
-      first.prev.next <- elt;
-      first.prev <- elt
-
-  (* conversion to enum *)
-  let to_enum d =
-    fun () ->
-      match !d with
-      | None -> (fun () -> None)
-      | Some first ->
-        let cur = ref first in (* current element of the list *)
-        let stop = ref false in (* are we done yet? *)
-        fun () ->
-          if !stop then None
-          else begin
-            let x = (!cur).content in
-            cur := (!cur).next;
-            (if !cur == first then stop := true); (* EOG, we made a full cycle *)
-            Some x
-          end
+  let to_gen l () =
+    let cur = ref l in
+    let i = ref 0 in
+    let rec next() = match !cur with
+    | Nil -> None
+    | Cons (a,n,l') ->
+        if !i = !n
+        then begin
+          cur := !l';
+          i := 0;
+          next()
+        end else begin
+          let y = a.(!i) in
+          incr i;
+          Some y
+        end
+    in
+    next
 end
 
 (** Store content of the generator in an enum *)
 let persistent gen =
-  let l = MList.create () in
-  iter (MList.push_back l) gen;
-  MList.to_enum l
+  let l = MList.of_gen gen in
+  MList.to_gen l
+
+(*$T
+  let g = 1--10 in let g' = persistent g in \
+    Restart.to_list g' = Restart.to_list g'
+  let g = 1--10 in let g' = persistent g in \
+    Restart.to_list g' = [1;2;3;4;5;6;7;8;9;10]
+*)
diff --git a/core/CCGen.mli b/core/CCGen.mli
index 18ddf1ec..c61670f6 100644
--- a/core/CCGen.mli
+++ b/core/CCGen.mli
@@ -109,7 +109,7 @@ module type S = sig
   val flatten : 'a gen t -> 'a t
     (** Flatten the enumeration of generators *)
 
-  val flatMap : ('a -> 'b gen) -> 'a t -> 'b t
+  val flat_map : ('a -> 'b gen) -> 'a t -> 'b t
     (** Monadic bind; each element is transformed to a sub-enum
         which is then iterated on, before the next element is processed,
         and so on. *)
@@ -127,19 +127,24 @@ module type S = sig
     (** n-th element, or Not_found
         @raise Not_found if the generator contains less than [n] arguments *)
 
+  val take_nth : int -> 'a t -> 'a t
+    (** [take_nth n g] returns every element of [g] whose index
+        is a multiple of [n]. For instance [take_nth 2 (1--10) |> to_list]
+        will return [1;3;5;7;9] *)
+
   val filter : ('a -> bool) -> 'a t -> 'a t
     (** Filter out elements that do not satisfy the predicate.  *)
 
-  val takeWhile : ('a -> bool) -> 'a t -> 'a t
+  val take_while : ('a -> bool) -> 'a t -> 'a t
     (** Take elements while they satisfy the predicate *)
 
-  val dropWhile : ('a -> bool) -> 'a t -> 'a t
+  val drop_while : ('a -> bool) -> 'a t -> 'a t
     (** Drop elements while they satisfy the predicate *)
 
-  val filterMap : ('a -> 'b option) -> 'a t -> 'b t
+  val filter_map : ('a -> 'b option) -> 'a t -> 'b t
     (** Maps some elements to 'b, drop the other ones *)
 
-  val zipIndex : 'a t -> (int * 'a) t
+  val zip_index : 'a t -> (int * 'a) t
     (** Zip elements with their index in the enum *)
 
   val unzip : ('a * 'b) t -> 'a t * 'b t
@@ -199,7 +204,7 @@ module type S = sig
     (** Succeeds if some pair of elements satisfy the predicate.
         Ignores elements of an iterator if the other runs dry. *)
 
-  val zipWith : ('a -> 'b -> 'c) -> 'a t -> 'b t -> 'c t
+  val zip_with : ('a -> 'b -> 'c) -> 'a t -> 'b t -> 'c t
     (** Combine common part of the enums (stops when one is exhausted) *)
 
   val zip : 'a t -> 'b t -> ('a * 'b) t
diff --git a/core/CCList.ml b/core/CCList.ml
index 14325802..cad0c945 100644
--- a/core/CCList.ml
+++ b/core/CCList.ml
@@ -74,9 +74,6 @@ let rec equal f l1 l2 = match l1, l2 with
   | [], _ | _, [] -> false
   | x1::l1', x2::l2' -> f x1 x2 && equal f l1' l2'
 
-(* difference list *)
-type 'a dlist = 'a list -> 'a list
-
 (* append difference lists *)
 let _d_append f1 f2 =
   fun l -> f1 (f2 l)
@@ -290,7 +287,7 @@ module Idx = struct
     Idx.insert [1;2;3] 1 10 = [1;10;2;3]
    *)
 
-  let rec remove l0 i =
+  let remove l0 i =
     let rec aux l acc i = match l with
       | [] -> l0
       | _::l' when i=0 -> List.rev_append acc l'
@@ -383,6 +380,7 @@ end
 type 'a sequence = ('a -> unit) -> unit
 type 'a gen = unit -> 'a option
 type 'a printer = Buffer.t -> 'a -> unit
+type 'a formatter = Format.formatter -> 'a -> unit
 
 let to_seq l k = List.iter k l
 let of_seq seq =
@@ -425,3 +423,14 @@ let pp ?(start="[") ?(stop="]") ?(sep=", ") pp_item buf l =
 (*$T
   CCPrint.to_string (pp CCPrint.int) [1;2;3] = "[1, 2, 3]"
   *)
+
+let print ?(start="[") ?(stop="]") ?(sep=", ") pp_item fmt l =
+  let rec print fmt l = match l with
+    | x::((y::xs) as l) ->
+      pp_item fmt x;
+      Format.pp_print_string fmt sep;
+      print fmt l
+    | x::[] -> pp_item fmt x
+    | [] -> ()
+  in
+  Format.fprintf fmt "@[%s%a%s@]" start print l stop
diff --git a/core/CCList.mli b/core/CCList.mli
index ecfa2388..0d84aac2 100644
--- a/core/CCList.mli
+++ b/core/CCList.mli
@@ -172,6 +172,7 @@ end
 type 'a sequence = ('a -> unit) -> unit
 type 'a gen = unit -> 'a option
 type 'a printer = Buffer.t -> 'a -> unit
+type 'a formatter = Format.formatter -> 'a -> unit
 
 val to_seq : 'a t -> 'a sequence
 val of_seq : 'a sequence -> 'a t
@@ -183,3 +184,6 @@ val of_gen : 'a gen -> 'a t
 
 val pp : ?start:string -> ?stop:string -> ?sep:string ->
          'a printer -> 'a t printer
+
+val print : ?start:string -> ?stop:string -> ?sep:string ->
+            'a formatter -> 'a t formatter
diff --git a/core/CCSequence.ml b/core/CCSequence.ml
index e5ddf09d..b2e15ded 100644
--- a/core/CCSequence.ml
+++ b/core/CCSequence.ml
@@ -91,7 +91,7 @@ let foldi f init seq =
     r := f !r !i elt;
     incr i);
   !r
-    
+
 (** Map objects of the sequence into other elements, lazily *)
 let map f seq =
   let seq_fun' k = seq (fun x -> k (f x)) in
@@ -144,97 +144,94 @@ let intersperse elem seq =
 
 (** Mutable unrolled list to serve as intermediate storage *)
 module MList = struct
-  type 'a t = {
-    content : 'a array;   (* elements of the node *)
-    mutable len : int;    (* number of elements in content *)
-    mutable tl : 'a t;    (* tail *)
-  } (** A list that contains some elements, and may point to another list *)
+  type 'a node =
+    | Nil
+    | Cons of 'a array * int ref * 'a node ref
 
-  let _empty () : 'a t = Obj.magic 0
-    (** Empty list, for the tl field *)
+  let of_seq seq =
+    let start = ref Nil in
+    let chunk_size = ref 8 in
+    (* fill the list. prev: tail-reference from previous node *)
+    let prev, cur = ref start, ref Nil in
+    seq
+      (fun x -> match !cur with
+        | Nil ->
+          let n = !chunk_size in
+          if n < 4096 then chunk_size := 2 * !chunk_size;
+          cur := Cons (Array.make n x, ref 1, ref Nil)
+        | Cons (a,n,next) ->
+          assert (!n < Array.length a);
+          a.(!n) <- x;
+          incr n;
+          if !n = Array.length a then begin
+            !prev := !cur;
+            prev := next;
+            cur := Nil
+          end
+      );
+    !prev := !cur;
+    !start
 
-  let make n =
-    assert (n > 0);
-    { content = Array.make n (Obj.magic 0);
-      len = 0;
-      tl = _empty ();
-    }
-
-  let rec is_empty l =
-    l.len = 0 && (l.tl == _empty () || is_empty l.tl)
-
-  let rec iter f l =
-    for i = 0 to l.len - 1 do f l.content.(i); done;
-    if l.tl != _empty () then iter f l.tl
+  let rec iter f l = match l with
+    | Nil -> ()
+    | Cons (a, n, tl) ->
+        for i=0 to !n - 1 do f a.(i) done;
+        iter f !tl
 
   let iteri f l =
-    let rec iteri i f l =
-      for j = 0 to l.len - 1 do f (i+j) l.content.(j); done;
-      if l.tl != _empty () then iteri (i+l.len) f l.tl
+    let rec iteri i f l = match l with
+    | Nil -> ()
+    | Cons (a, n, tl) ->
+        for j=0 to !n - 1 do f (i+j) a.(j) done;
+        iteri (i+ !n) f !tl
     in iteri 0 f l
 
-  let rec iter_rev f l =
-    (if l.tl != _empty () then iter_rev f l.tl);
-    for i = l.len - 1 downto 0 do f l.content.(i); done
+  let rec iter_rev f l = match l with
+    | Nil -> ()
+    | Cons (a, n, tl) ->
+        iter_rev f !tl;
+        for i = !n-1 downto 0 do f a.(i) done
 
   let length l =
-    let rec len acc l =
-      if l.tl == _empty () then acc+l.len else len (acc+l.len) l.tl
+    let rec len acc l = match l with
+      | Nil -> acc
+      | Cons (_, n, tl) -> len (acc+ !n) !tl
     in len 0 l
 
   (** Get element by index *)
-  let rec get l i =
-    if i < l.len then l.content.(i)
-    else if i >= l.len && l.tl == _empty () then raise (Invalid_argument "MList.get")
-    else get l.tl (i - l.len)
+  let rec get l i = match l with
+    | Nil -> raise (Invalid_argument "MList.get")
+    | Cons (a, n, _) when i < !n -> a.(i)
+    | Cons (_, n, tl) -> get !tl (i- !n)
 
-  (** Push [x] at the end of the list. It returns the block in which the
-      element is inserted. *)
-  let rec push x l =
-    if l.len = Array.length l.content
-      then begin (* insert in the next block *)
-        (if l.tl == _empty () then
-          let n = Array.length l.content in
-          l.tl <- make (n + n lsr 1));
-        push x l.tl
-      end else begin  (* insert in l *)
-        l.content.(l.len) <- x;
-        l.len <- l.len + 1;
-        l
-      end
+  let to_seq l k = iter k l
 
-  (** Reverse list (in place), and returns the new head *)
-  let rev l =
-    let rec rev prev l =
-      (* reverse array *)
-      for i = 0 to (l.len-1) / 2 do
-        let x = l.content.(i) in
-        l.content.(i) <- l.content.(l.len - i - 1);
-        l.content.(l.len - i - 1) <- x;
-      done;
-      (* reverse next block *)
-      let l' = l.tl in
-      l.tl <- prev;
-      if l' == _empty () then l else rev l l'
-    in
-    rev (_empty ()) l
+  let _to_next arg l =
+    let cur = ref l in
+    let i = ref 0 in (* offset in cons *)
+    let rec get_next _ = match !cur with
+      | Nil -> None
+      | Cons (_, n, tl) when !i = !n ->
+          cur := !tl;
+          i := 0;
+          get_next arg
+      | Cons (a, n, _) ->
+          let x = a.(!i) in
+          incr i;
+          Some x
+    in get_next
 
-  (** Build a MList of elements of the Seq. The optional argument indicates
-      the size of the blocks *)
-  let of_seq ?(size=8) seq =
-    (* read sequence into a MList.t *)
-    let start = make size in
-    let l = ref start in
-    seq (fun x -> l := push x !l);
-    start
+  let to_gen l = _to_next () l
+
+  let to_stream l =
+    Stream.from (_to_next 42 l)  (* 42=magic cookiiiiiie *)
 end
 
 (** Iterate on the sequence, storing elements in a data structure.
     The resulting sequence can be iterated on as many times as needed. *)
-let persistent ?(blocksize=64) seq =
-  if blocksize < 2 then failwith "Sequence.persistent: blocksize too small";
-  let l = MList.of_seq ~size:blocksize seq in
-  from_iter (fun k -> MList.iter k l)
+let persistent seq =
+  let l = MList.of_seq seq in
+  MList.to_seq l
 
 (** Sort the sequence. Eager, O(n) ram and O(n ln(n)) time. *)
 let sort ?(cmp=Pervasives.compare) seq =
@@ -316,14 +313,19 @@ let scan f acc seq =
       let acc = ref acc in
       seq (fun elt -> let acc' = f !acc elt in k acc'; acc := acc'))
 
-(** Max element of the sequence, using the given comparison
-    function. A default element has to be provided. *)
-let max ?(lt=fun x y -> x < y) seq m =
-  fold (fun m x -> if lt m x then x else m) m seq
+let max ?(lt=fun x y -> x < y) seq =
+  let ret = ref None in
+  seq (fun x -> match !ret with
+    | None -> ret := Some x
+    | Some y -> if lt y x then ret := Some x);
+  !ret
 
-(** Min element of the sequence, using the given comparison function *)
-let min ?(lt=fun x y -> x < y) seq m =
-  fold (fun m x -> if lt x m then x else m) m seq
+let min ?(lt=fun x y -> x < y) seq =
+  let ret = ref None in
+  seq (fun x -> match !ret with
+    | None -> ret := Some x
+    | Some y -> if lt x y then ret := Some x);
+  !ret
 
 exception ExitSequence
 
@@ -337,7 +339,7 @@ let take n seq =
           incr count;
           k x;
           if !count = n then raise ExitSequence)
-    with ExitSequence -> ()
+      with ExitSequence -> ()
 
 (** Drop the [n] first elements of the sequence *)
 let drop n seq =
@@ -470,14 +472,8 @@ let of_stream s =
 
 (** Convert to a stream. The sequence is made persistent. *)
 let to_stream seq =
-  let l = ref (MList.of_seq seq) in
-  let i = ref 0 in
-  let rec get_next () =
-    if !l == MList._empty () then None
-    else if (!l).MList.len = !i then (l := (!l).MList.tl; i := 0; get_next ())
-    else let x = (!l).MList.content.(!i) in (incr i; Some x)
-  in
-  Stream.from (fun _ -> get_next ())
+  let l = MList.of_seq seq in
+  MList.to_stream l
 
 (** Push elements of the sequence on the stack *)
 let to_stack s seq = iter (fun x -> Stack.push x s) seq
@@ -520,7 +516,7 @@ let hashtbl_values h =
   from_iter (fun k -> Hashtbl.iter (fun a b -> k b) h)
 
 let of_str s = from_iter (fun k -> String.iter k s)
-    
+
 let to_str seq =
   let b = Buffer.create 64 in
   iter (fun c -> Buffer.add_char b c) seq;
@@ -541,6 +537,10 @@ let int_range ~start ~stop =
   fun k ->
     for i = start to stop do k i done
 
+let int_range_dec ~start ~stop =
+  fun k ->
+    for i = start downto stop do k i done
+
 (** Convert the given set to a sequence. The set module must be provided. *)
 let of_set (type s) (type v) m set =
   let module S = (val m : Set.S with type t = s and type elt = v) in
@@ -554,6 +554,21 @@ let to_set (type s) (type v) m seq =
     (fun set x -> S.add x set)
     S.empty seq
 
+type 'a gen = unit -> 'a option
+
+let of_gen g =
+  (* consume the generator to build a MList *)
+  let rec iter1 k = match g () with
+    | None -> ()
+    | Some x -> k x; iter1 k
+  in
+  let l = MList.of_seq iter1 in
+  MList.to_seq l
+
+let to_gen seq =
+  let l = MList.of_seq seq in
+  MList.to_gen l
+
 (** {2 Functorial conversions between sets and sequences} *)
 
 module Set = struct
@@ -571,7 +586,7 @@ module Set = struct
 
     include X
   end
-    
+
   (** Functor to build an extended Set module from an ordered type *)
   module Make(X : Set.OrderedType) = struct
     module MySet = Set.Make(X)
@@ -630,70 +645,23 @@ let random_array a =
 
 let random_list l = random_array (Array.of_list l)
 
-(** {2 Type-classes} *)
-
-module TypeClass = struct
-  (** {3 Classes} *)
-  type ('a,'b) sequenceable = {
-    to_seq : 'b -> 'a t;
-    of_seq : 'a t -> 'b;
-  }
-
-  type ('a,'b) addable = {
-    empty : 'b;
-    add : 'b -> 'a -> 'b;
-  }
-
-  type 'a monoid = ('a,'a) addable
-
-  type ('a,'b) iterable = {
-    iter : ('a -> unit) -> 'b -> unit;
-  }
-
-  (** {3 Instances} *)
-
-  let (sequenceable : ('a,'a t) sequenceable) = {
-    to_seq = (fun seq -> seq);
-    of_seq = (fun seq -> seq);
-  }
-
-  let (iterable : ('a, 'a t) iterable) = {
-    iter = (fun f seq -> iter f seq);
-  }
-
-  let (monoid : 'a t monoid) = {
-    empty = empty;
-    add = (fun s1 s2 -> append s1 s2);
-  }
-
-  (** {3 Conversions} *)
-
-  let of_iterable iterable x =
-    from_iter (fun k -> iterable.iter k x)
-
-
-  let to_addable addable seq =
-    fold addable.add addable.empty seq
-end
-
 (** {2 Infix functions} *)
 
 module Infix = struct
   let (--) i j = int_range ~start:i ~stop:j
 
-  let (|>) x f = f x
-
-  let (@@) a b = append a b
-
-  let (>>=) x f = flatMap f x
+  let (--^) i j = int_range_dec ~start:i ~stop:j
 end
 
+include Infix
+
 (** {2 Pretty printing of sequences} *)
 
 (** Pretty print a sequence of ['a], using the given pretty printer
     to print each elements. An optional separator string can be provided. *)
-let pp_seq ?(sep=", ") pp_elt formatter seq =
+let print ?(start="") ?(stop="") ?(sep=", ") pp_elt formatter seq =
   let first = ref true in
+  Format.pp_print_string formatter start;
   iter
     (fun x -> 
       (if !first then first := false
@@ -702,4 +670,22 @@ let pp_seq ?(sep=", ") pp_elt formatter seq =
           Format.pp_print_cut formatter ();
         end);
       pp_elt formatter x)
-    seq
+    seq;
+  Format.pp_print_string formatter stop;
+  ()
+
+let pp ?(start="") ?(stop="") ?(sep=", ") pp_elt buf seq =
+  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_elt buf x)
+    seq;
+  Buffer.add_string buf stop;
+  ()
+
+let to_string ?start ?stop ?sep pp_elt seq =
+  let buf = Buffer.create 25 in
+  pp ?start ?stop ?sep pp_elt buf seq;
+  Buffer.contents buf
diff --git a/core/CCSequence.mli b/core/CCSequence.mli
index 86b6ba34..9ac6c616 100644
--- a/core/CCSequence.mli
+++ b/core/CCSequence.mli
@@ -151,15 +151,11 @@ val fmap : ('a -> 'b option) -> 'a t -> 'b t
 val intersperse : 'a -> 'a t -> 'a t
   (** Insert the single element between every element of the sequence *)
 
-val persistent : ?blocksize:int -> 'a t -> 'a t
+val persistent : 'a t -> 'a t
   (** Iterate on the sequence, storing elements in a data structure.
       The resulting sequence can be iterated on as many times as needed.
       {b Note}: calling persistent on an already persistent sequence
-      will still make a new copy of the sequence!
-      
-      @param blocksize the size of chunks in the unrolled list
-        used to store elements. Use bigger values for bigger sequences.
-        Default: 64 *)
+      will still make a new copy of the sequence! *)
 
 val sort : ?cmp:('a -> 'a -> int) -> 'a t -> 'a t
   (** Sort the sequence. Eager, O(n) ram and O(n ln(n)) time.
@@ -195,12 +191,14 @@ val unfoldr : ('b -> ('a * 'b) option) -> 'b -> 'a t
 val scan : ('b -> 'a -> 'b) -> 'b -> 'a t -> 'b t
   (** Sequence of intermediate results *)
 
-val max : ?lt:('a -> 'a -> bool) -> 'a t -> 'a -> 'a
-  (** Max element of the sequence, using the given comparison
-      function. A default element has to be provided. *)
+val max : ?lt:('a -> 'a -> bool) -> 'a t -> 'a option
+  (** Max element of the sequence, using the given comparison function.
+      @return None if the sequence is empty, Some [m] where [m] is the maximal
+      element otherwise *)
 
-val min : ?lt:('a -> 'a -> bool) -> 'a t -> 'a -> 'a
-  (** Min element of the sequence, using the given comparison function *)
+val min : ?lt:('a -> 'a -> bool) -> 'a t -> 'a option
+  (** Min element of the sequence, using the given comparison function.
+      see {!max} for more details. *)
 
 val take : int -> 'a t -> 'a t
   (** Take at most [n] elements from the sequence. Works on infinite
@@ -243,7 +241,7 @@ val map2_2 : ('a -> 'b -> 'c) -> ('a -> 'b -> 'd) -> ('a, 'b) t2 -> ('c, 'd) t2
 val to_list : 'a t -> 'a list
 
 val to_rev_list : 'a t -> 'a list
-  (** Get the list of the reversed sequence (more efficient) *)
+  (** Get the list of the reversed sequence (more efficient than {!to_list}) *)
 
 val of_list : 'a list -> 'a t
 
@@ -315,7 +313,12 @@ val to_buffer : char t -> Buffer.t -> unit
   (** Copy content of the sequence into the buffer *)
 
 val int_range : start:int -> stop:int -> int t
-  (** Iterator on integers in [start...stop] by steps 1 *)
+  (** Iterator on integers in [start...stop] by steps 1. Also see
+      {!(--)} for an infix version. *)
+
+val int_range_dec : start:int -> stop:int -> int t
+  (** Iterator on decreasing integers in [stop...start] by steps -1.
+      See {!(--^)} for an infix version *)
 
 val of_set : (module Set.S with type elt = 'a and type t = 'b) -> 'b -> 'a t
   (** Convert the given set to a sequence. The set module must be provided. *)
@@ -323,6 +326,14 @@ val of_set : (module Set.S with type elt = 'a and type t = 'b) -> 'b -> 'a t
 val to_set : (module Set.S with type elt = 'a and type t = 'b) -> 'a t -> 'b
   (** Convert the sequence to a set, given the proper set module *)
 
+type 'a gen = unit -> 'a option
+
+val of_gen : 'a gen -> 'a t
+  (** Traverse eagerly the generator and build a sequence from it *)
+
+val to_gen : 'a t -> 'a gen
+  (** Make the sequence persistent (O(n)) and then iterate on it. Eager. *)
+
 (** {2 Functorial conversions between sets and sequences} *)
 
 module Set : sig
@@ -375,51 +386,30 @@ val random_list : 'a list -> 'a t
   (** Infinite sequence of random elements of the list. Basically the
       same as {!random_array}. *)
 
-(** {2 Type-classes} *)
-
-module TypeClass : sig
-  (** {3 Classes} *)
-  type ('a,'b) sequenceable = {
-    to_seq : 'b -> 'a t;
-    of_seq : 'a t -> 'b;
-  }
-
-  type ('a,'b) addable = {
-    empty : 'b;
-    add : 'b -> 'a -> 'b;
-  }
-
-  type 'a monoid = ('a,'a) addable
-
-  type ('a,'b) iterable = {
-    iter : ('a -> unit) -> 'b -> unit;
-  }
-
-  (** {3 Instances} *)
-
-  val sequenceable : ('a,'a t) sequenceable
-  val iterable : ('a,'a t) iterable
-  val monoid : 'a t monoid
-
-  (** {3 Conversions} *)
-
-  val of_iterable : ('a,'b) iterable -> 'b -> 'a t
-  val to_addable : ('a,'b) addable -> 'a t -> 'b
-end
-
 (** {2 Infix functions} *)
 
 module Infix : sig
   val (--) : int -> int -> int t
 
-  val (|>) : 'a -> ('a -> 'b) -> 'b
-
-  val (@@) : 'a t -> 'a t -> 'a t
+  val (--^) : int -> int -> int t
+    (** [a --^ b] is the range of integers from [b] to [a], both included,
+        in decreasing order (starts from [a]).
+        It will therefore be empty if [a < b]. *)
 end
 
+include module type of Infix
+
 (** {2 Pretty printing of sequences} *)
 
-val pp_seq : ?sep:string -> (Format.formatter -> 'a -> unit) ->
+val print : ?start:string -> ?stop:string -> ?sep:string ->
+            (Format.formatter -> 'a -> unit) ->
              Format.formatter -> 'a t -> unit
   (** Pretty print a sequence of ['a], using the given pretty printer
       to print each elements. An optional separator string can be provided. *)
+
+val pp : ?start:string -> ?stop:string -> ?sep:string ->
+         (Buffer.t -> 'a -> unit) ->
+          Buffer.t -> 'a t -> unit
+
+val to_string : ?start:string -> ?stop:string -> ?sep:string ->
+                (Buffer.t -> 'a -> unit) -> 'a t -> string
diff --git a/core/CCVector.ml b/core/CCVector.ml
index 283f293a..0ea564e7 100644
--- a/core/CCVector.ml
+++ b/core/CCVector.ml
@@ -37,8 +37,6 @@ let create i =
     vec = Array.create i (Obj.magic None);
   }
 
-(** resize the underlying array so that it can contains the
-    given number of elements *)
 let resize v newcapacity =
   assert (newcapacity >= v.size);
   let new_vec = Array.create newcapacity (Obj.magic None) in
@@ -46,7 +44,6 @@ let resize v newcapacity =
   v.vec <- new_vec;
   ()
 
-(** Be sure that [v] can contain [size] elements, resize it if needed. *)
 let ensure v size =
   if v.size < size
     then
diff --git a/core/CCVector.mli b/core/CCVector.mli
index 6e973da7..697c601e 100644
--- a/core/CCVector.mli
+++ b/core/CCVector.mli
@@ -26,100 +26,104 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 (** {1 Growable, mutable vector} *)
 
 type 'a t
-  (** the type of a vector of 'a *)
+(** the type of a vector of 'a *)
 
 type 'a sequence = ('a -> unit) -> unit
 
 val create : int -> 'a t
-  (** create a vector of given initial capacity *)
+(** create a vector of given initial capacity *)
 
 val clear : 'a t -> unit
-  (** clear the content of the vector *)
+(** clear the content of the vector *)
+
+val ensure : 'a t -> int -> unit
+(** Ensure that the vector can contain that much elements, resizing it
+    if required *)
 
 val is_empty : 'a t -> bool
-  (** is the vector empty? *)
+(** is the vector empty? *)
 
 val push : 'a t -> 'a -> unit
-  (** add an element at the end of the vector *)
+(** add an element at the end of the vector *)
 
 val append : 'a t -> 'a t -> unit
-  (** [append a b] adds all elements of b to a *)
+(** [append a b] adds all elements of b to a *)
 
 val append_array : 'a t -> 'a array -> unit
-  (** same as append, with an array *)
+(** same as append, with an array *)
 
 val append_seq : 'a t -> 'a sequence -> unit
-  (** Append content of sequence *)
+(** Append content of sequence *)
 
 val pop : 'a t -> 'a
-  (** remove last element, or raise a Failure if empty *)
+(** remove last element, or raise a Failure if empty *)
 
 val copy : 'a t -> 'a t
-  (** shallow copy *)
+(** shallow copy *)
 
 val shrink : 'a t -> int -> unit
-  (** shrink to the given size (remove elements above this size) *)
+(** shrink to the given size (remove elements above this size) *)
 
 val member : ?eq:('a -> 'a -> bool) -> 'a t -> 'a -> bool
-  (** is the element a member of the vector? *)
+(** is the element a member of the vector? *)
 
 val sort : ?cmp:('a -> 'a -> int) -> 'a t -> unit
-  (** sort the array in place*)
+(** sort the array in place*)
 
 val uniq_sort : ?cmp:('a -> 'a -> int) -> 'a t -> unit
-  (** sort the array and remove duplicates in place*)
+(** sort the array and remove duplicates in place*)
 
 val iter : 'a t -> ('a -> unit) -> unit
-  (** iterate on the vector *)
+(** iterate on the vector *)
 
 val iteri : 'a t -> (int -> 'a -> unit) -> unit
-  (** iterate on the vector with indexes *)
+(** iterate on the vector with indexes *)
 
 val map : 'a t -> ('a -> 'b) -> 'b t
-  (** map elements of the vector *)
+(** map elements of the vector *)
 
 val filter : 'a t -> ('a -> bool) -> 'a t
-  (** filter elements from vector *)
+(** filter elements from vector *)
 
 val fold : 'a t -> 'b -> ('b -> 'a -> 'b) -> 'b
-  (** fold on elements of the vector *)
+(** fold on elements of the vector *)
 
 val exists : 'a t -> ('a -> bool) -> bool
-  (** existential test *)
+(** existential test *)
 
 val for_all : 'a t -> ('a -> bool) -> bool
-  (** universal test *)
+(** universal test *)
 
 val find : 'a t -> ('a -> bool) -> 'a
-  (** find an element that satisfies the predicate, or Not_found *)
+(** find an element that satisfies the predicate, or Not_found *)
 
 val get : 'a t -> int -> 'a
-  (** access element, or Failure if bad index *)
+(** access element, or Failure if bad index *)
 
 val set : 'a t -> int -> 'a -> unit
-  (** access element, or Failure if bad index *)
+(** access element, or Failure if bad index *)
 
 val rev : 'a t -> unit
-  (** Reverse array in place *)
+(** Reverse array in place *)
 
 val size : 'a t -> int
-  (** number of elements in vector *)
+(** number of elements in vector *)
 
 val length : _ t -> int
-  (** Synonym for {! size} *)
+(** Synonym for {! size} *)
 
 val unsafe_get_array : 'a t -> 'a array
-  (** Access the underlying *shared* array (do not modify!).
-      [unsafe_get_array v] is longer than [size v], but elements at higher
-      index than [size v] are undefined (do not access!). *)
+(** Access the underlying *shared* array (do not modify!).
+    [unsafe_get_array v] is longer than [size v], but elements at higher
+    index than [size v] are undefined (do not access!). *)
 
 val of_seq : ?init:'a t -> 'a sequence -> 'a t
 
 val to_seq : 'a t -> 'a sequence
 
 val slice : 'a t -> int -> int -> 'a sequence
-  (** [slice v start len] is the sequence of elements from [v.(start)]
-      to [v.(start+len)] included. *)
+(** [slice v start len] is the sequence of elements from [v.(start)]
+    to [v.(start+len)] included. *)
 
 val from_array : 'a array -> 'a t
 val from_list : 'a list -> 'a t
diff --git a/misc/lazyGraph.ml b/misc/lazyGraph.ml
index 02201ad4..82a664d8 100644
--- a/misc/lazyGraph.ml
+++ b/misc/lazyGraph.ml
@@ -578,13 +578,13 @@ module Dot = struct
       (function
         | Full.EnterVertex (v, attrs, _, _) ->
           Format.fprintf formatter "  @[<h>%a [%a];@]@." pp_vertex v
-            (CCSequence.pp_seq ~sep:"," print_attribute) (CCSequence.of_list attrs)
+            (CCList.print ~sep:"," print_attribute) attrs
         | Full.ExitVertex _ -> ()
         | Full.MeetEdge (v2, attrs, v1, _) ->
           Format.fprintf formatter "  @[<h>%a -> %a [%a];@]@."
             pp_vertex v1 pp_vertex v2
-            (CCSequence.pp_seq ~sep:"," print_attribute)
-            (CCSequence.of_list attrs))
+            (CCList.print ~sep:"," print_attribute)
+            attrs)
       events;
     (* close *)
     Format.fprintf formatter "}@]@;@?";
diff --git a/misc/persistentGraph.ml b/misc/persistentGraph.ml
index cd23cab1..1928e6f5 100644
--- a/misc/persistentGraph.ml
+++ b/misc/persistentGraph.ml
@@ -346,15 +346,15 @@ let pp ~name ?vertices
       let attributes = print_edge v1 e v2 in
       Format.fprintf formatter "  @[<h>%a -> %a [%a];@]@."
         pp_vertex v1 pp_vertex v2
-        (CCSequence.pp_seq ~sep:"," print_attribute)
-        (CCSequence.of_list attributes))
+        (CCList.print ~sep:"," print_attribute)
+        attributes)
     (to_seq graph);
   (* print vertices *)
   PHashtbl.iter
     (fun v _ ->
       let attributes = print_vertex v in
       Format.fprintf formatter "  @[<h>%a [%a];@]@." pp_vertex v
-        (CCSequence.pp_seq ~sep:"," print_attribute) (CCSequence.of_list attributes))
+        (CCList.print ~sep:"," print_attribute) attributes)
     vertices;
   (* close *)
   Format.fprintf formatter "}@]@;";
diff --git a/tests/benchs.ml b/tests/benchs.ml
index 51f96ccf..bce6dd0c 100644
--- a/tests/benchs.ml
+++ b/tests/benchs.ml
@@ -306,7 +306,7 @@ let bench_enum () =
   let enum () =
     let open CCGen in
     let seq = int_range 0 n in
-    let seq = flatMap (fun x -> int_range x (x+10)) seq in
+    let seq = flat_map (fun x -> int_range x (x+10)) seq in
     fold (+) 0 seq in
   Bench.bench
     [ "sequence.flatMap", seq;