diff --git a/core/CCLinq.ml b/core/CCLinq.ml
index 489740ee..4d916d9b 100644
--- a/core/CCLinq.ml
+++ b/core/CCLinq.ml
@@ -35,7 +35,13 @@ type 'a hash = 'a -> int
 
 let _id x = x
 
-module Map = struct
+type 'a collection =
+  | Seq : 'a sequence -> 'a collection
+  | List : 'a list -> 'a collection
+  | Set : (module CCSequence.Set.S
+           with type elt = 'a and type t = 'b) * 'b -> 'a collection
+
+module PMap = struct
   type ('a, 'b) t = {
     is_empty : unit -> bool;
     size : unit -> int; (** Number of keys *)
@@ -49,6 +55,7 @@ module Map = struct
     | None -> false
     | Some _ -> true
   let to_seq m = m.to_seq
+  let fold f acc m = m.fold f acc
   let size m = m.size ()
 
   type ('a, 'b) build = {
@@ -144,7 +151,39 @@ module Map = struct
     | None -> raise Not_found
     | Some x -> x
 
+  (* map values *)
+  let map f m = {
+    is_empty = m.is_empty;
+    size = m.size;
+    get = (fun k -> match m.get k with
+      | None -> None
+      | Some v -> Some (f v)
+    );
+    to_seq = CCSequence.map (fun (x,y) -> x, f y) m.to_seq;
+    fold = (fun f' acc ->
+      m.fold (fun acc x y -> f' acc x (f y)) acc
+    );
+  }
+
   let to_list m = m.to_seq |> CCSequence.to_rev_list
+
+  let to_coll m = Seq m.to_seq
+
+  let reverse ~build m =
+    let build = make ~build () in
+    to_seq m
+      |> CCSequence.map (fun (x,y) -> y,x)
+      |> multimap_of_seq ~build
+
+  let reverse_multimap ~build m =
+    let build = make ~build () in
+    to_seq m
+      |> CCSequence.flatMap
+        (fun (x,l) -> 
+          CCSequence.of_list l
+          |> CCSequence.map (fun y -> y,x)
+        )
+      |> multimap_of_seq ~build
 end
 
 type 'a search_result =
@@ -155,21 +194,15 @@ type ('a,'b,'key,'c) join_descr = {
   join_key1 : 'a -> 'key;
   join_key2 : 'b -> 'key;
   join_merge : 'key -> 'a -> 'b -> 'c option;
-  join_build : 'key Map.build_method;
+  join_build : 'key PMap.build_method;
 }
 
 type ('a,'b) group_join_descr = {
   gjoin_proj : 'b -> 'a;
-  gjoin_build : 'a Map.build_method;
+  gjoin_build : 'a PMap.build_method;
 }
 
 module Coll = struct
-  type 'a t =
-    | Seq : 'a sequence -> 'a t
-    | List : 'a list -> 'a t
-    | Set : (module CCSequence.Set.S
-             with type elt = 'a and type t = 'b) * 'b -> 'a t
-
   let of_seq s = Seq s
   let of_list l = List l
   let of_array a = Seq (CCSequence.of_array a)
@@ -299,12 +332,12 @@ module Coll = struct
     let build1 =
       to_seq c1
       |> CCSequence.map (fun x -> join.join_key1 x, x)
-      |> Map.multimap_of_seq ~build:(Map.make ~build:join.join_build ())
+      |> PMap.multimap_of_seq ~build:(PMap.make ~build:join.join_build ())
     in
     let l = CCSequence.fold
       (fun acc y ->
         let key = join.join_key2 y in
-        match Map.get build1 key with
+        match PMap.get build1 key with
         | None -> acc
         | Some l1 ->
             List.fold_left
@@ -317,29 +350,29 @@ module Coll = struct
     of_list l
 
   let do_group_join ~gjoin c1 c2 =
-    let build = Map.make ~build:gjoin.gjoin_build () in
-    to_seq c1 (fun x -> Map.add build x []);
+    let build = PMap.make ~build:gjoin.gjoin_build () in
+    to_seq c1 (fun x -> PMap.add build x []);
     to_seq c2
       (fun y ->
         (* project [y] into some element of [c1] *)
         let x = gjoin.gjoin_proj y in
-        Map.update build x
+        PMap.update build x
           (function
             | None -> None   (* [x] not present, ignore! *)
             | Some l -> Some (y::l)
           )
       );
-    Map.build_get build
+    PMap.build_get build
 
   let do_product c1 c2 =
     let s1 = to_seq c1 and s2 = to_seq c2 in
     of_seq (CCSequence.product s1 s2)
 
   let do_union ~build c1 c2 =
-    let build = Map.make ~build () in
-    to_seq c1 (fun x -> Map.add build x ());
-    to_seq c2 (fun x -> Map.add build x ());
-    Map.to_seq (Map.build_get build)
+    let build = PMap.make ~build () in
+    to_seq c1 (fun x -> PMap.add build x ());
+    to_seq c2 (fun x -> PMap.add build x ());
+    PMap.to_seq (PMap.build_get build)
       |> CCSequence.map fst
       |> of_seq
 
@@ -348,11 +381,11 @@ module Coll = struct
     | InterDone  (* already output *)
 
   let do_inter ~build c1 c2 =
-    let build = Map.make ~build () in
+    let build = PMap.make ~build () in
     let l = ref [] in
-    to_seq c1 (fun x -> Map.add build x InterLeft);
+    to_seq c1 (fun x -> PMap.add build x InterLeft);
     to_seq c2 (fun x ->
-      Map.update build x
+      PMap.update build x
         (function
            | None -> Some InterDone
            | Some InterDone as foo -> foo
@@ -364,17 +397,15 @@ module Coll = struct
     of_list !l
 
   let do_diff ~build c1 c2 =
-    let build = Map.make ~build () in
-    to_seq c2 (fun x -> Map.add build x ());
-    let map = Map.build_get build in
+    let build = PMap.make ~build () in
+    to_seq c2 (fun x -> PMap.add build x ());
+    let map = PMap.build_get build in
     (* output elements of [c1] not in [map] *)
     to_seq c1
-      |> CCSequence.filter (fun x -> not (Map.mem map x))
+      |> CCSequence.filter (fun x -> not (PMap.mem map x))
       |> of_seq
 end
 
-type 'a collection = 'a Coll.t
-
 (** {2 Query operators} *)
 
 type (_,_) safety =
@@ -382,10 +413,12 @@ type (_,_) safety =
   | Unsafe : ('a, 'a) safety
 
 type (_, _) unary =
-  | Map : ('a -> 'b) -> ('a collection, 'b collection) unary
+  | PMap : ('a -> 'b) -> ('a collection, 'b collection) unary
   | GeneralMap : ('a -> 'b) -> ('a, 'b) unary
   | Filter : ('a -> bool) -> ('a collection, 'a collection) unary
   | Fold : ('b -> 'a -> 'b) * 'b -> ('a collection, 'b) unary
+  | FoldMap : ('acc -> 'a -> 'b -> 'acc) * 'acc
+    -> (('a,'b) PMap.t, 'acc) unary
   | Reduce : ('c, 'd) safety * ('a -> 'b) * ('a -> 'b -> 'b) * ('b -> 'c)
     -> ('a collection, 'd) unary
   | Size : ('a collection, int) unary
@@ -401,10 +434,11 @@ type (_, _) unary =
       failure : 'b;
     > -> ('a collection, 'b) unary
   | Contains : 'a equal * 'a -> ('a collection, bool) unary
-  | Get : ('b,'c) safety * 'a -> (('a,'b) Map.t, 'c) unary
-  | GroupBy : 'b Map.build_method * ('a -> 'b)
-    -> ('a collection, ('b,'a list) Map.t) unary
-  | Count : 'a Map.build_method -> ('a collection, ('a, int) Map.t) unary
+  | Get : ('b,'c) safety * 'a -> (('a,'b) PMap.t, 'c) unary
+  | GroupBy : 'b PMap.build_method * ('a -> 'b)
+    -> ('a collection, ('b,'a list) PMap.t) unary
+  | Count : 'a PMap.build_method -> ('a collection, ('a, int) PMap.t) unary
+  | Lazy : ('a lazy_t, 'a) unary
 
 type set_op =
   | Union
@@ -415,10 +449,10 @@ type (_, _, _) binary =
   | Join : ('a, 'b, 'key, 'c) join_descr
     -> ('a collection, 'b collection, 'c collection) binary
   | GroupJoin : ('a, 'b) group_join_descr
-    -> ('a collection, 'b collection, ('a, 'b list) Map.t) binary
+    -> ('a collection, 'b collection, ('a, 'b list) PMap.t) binary
   | Product : ('a collection, 'b collection, ('a*'b) collection) binary
   | Append : ('a collection, 'a collection, 'a collection) binary
-  | SetOp : set_op * 'a Map.build_method
+  | SetOp : set_op * 'a PMap.build_method
     -> ('a collection, 'a collection, 'a collection) binary
 
 (* type of queries that return a 'a *)
@@ -431,18 +465,30 @@ and 'a t =
 
 let start x = Start x
 
-let start_list l =
+let of_list l =
   Start (Coll.of_list l)
 
-let start_array a =
+let of_array a =
   Start (Coll.of_array a)
 
-let start_hashtbl h =
+let of_array_i a =
+  Start (CCSequence.of_array_i a |> Coll.of_seq)
+
+let of_hashtbl h =
   Start (Coll.of_seq (CCSequence.of_hashtbl h))
 
-let start_seq seq =
+let of_seq seq =
   Start (Coll.of_seq seq)
 
+let of_queue q =
+  Start (CCSequence.of_queue q |> Coll.of_seq)
+
+let of_stack s =
+  Start (CCSequence.of_stack s |> Coll.of_seq)
+
+let of_string s =
+  Start (CCSequence.of_str s |> Coll.of_seq)
+
 (** {6 Execution} *)
 
 let rec _optimize : type a. a t -> a t
@@ -456,32 +502,32 @@ let rec _optimize : type a. a t -> a t
     | Bind _ -> q  (* cannot optimize before execution *)
 and _optimize_unary : type a b. (a,b) unary -> a t -> b t
   = fun u q -> match u, q with
-    | Map f, Unary (Map g, q') ->
-        _optimize_unary (Map (fun x -> f (g x))) q'
-    | Filter p, Unary (Map f, cont) ->
+    | PMap f, Unary (PMap g, q') ->
+        _optimize_unary (PMap (fun x -> f (g x))) q'
+    | Filter p, Unary (PMap f, cont) ->
         _optimize_unary
           (FilterMap (fun x -> let y = f x in if p y then Some y else None))
           cont
-    | Map f, Unary (Filter p, cont) ->
+    | PMap f, Unary (Filter p, cont) ->
         _optimize_unary
           (FilterMap (fun x -> if p x then Some (f x) else None))
           cont
-    | Map f, Binary (Append, q1, q2) ->
+    | PMap f, Binary (Append, q1, q2) ->
         _optimize_binary Append (Unary (u, q1)) (Unary (u, q2))
     | Filter p, Binary (Append, q1, q2) ->
         _optimize_binary Append (Unary (u, q1)) (Unary (u, q2))
-    | Fold (f,acc), Unary (Map f', cont) ->
+    | Fold (f,acc), Unary (PMap f', cont) ->
         _optimize_unary
           (Fold ((fun acc x -> f acc (f' x)), acc))
           cont
-    | Reduce (safety, start, mix, stop), Unary (Map f, cont) ->
+    | Reduce (safety, start, mix, stop), Unary (PMap f, cont) ->
         _optimize_unary
           (Reduce (safety,
             (fun x -> start (f x)),
             (fun x acc -> mix (f x) acc),
             stop))
           cont
-    | Size, Unary (Map _, cont) ->
+    | Size, Unary (PMap _, cont) ->
         _optimize_unary Size cont  (* ignore the map! *)
     | Size, Unary (Sort _, cont) ->
         _optimize_unary Size cont
@@ -494,10 +540,11 @@ and _optimize_binary : type a b c. (a,b,c) binary -> a t -> b t -> c t
 (* apply a unary operator on a collection *)
 let _do_unary : type a b. (a,b) unary -> a -> b
 = fun u c -> match u with
-  | Map f -> Coll.map f c
+  | PMap f -> Coll.map f c
   | GeneralMap f -> f c
   | Filter p -> Coll.filter p c
   | Fold (f, acc) -> Coll.fold f acc c
+  | FoldMap (f, acc) -> PMap.fold f acc c
   | Reduce (safety, start, mix, stop) ->
       let acc = Coll.to_seq c
         |> CCSequence.fold
@@ -526,16 +573,17 @@ let _do_unary : type a b. (a,b) unary -> a -> b
   | Sort cmp -> Coll.sort cmp c
   | Distinct cmp -> Coll.distinct ~cmp c
   | Search obj -> Coll.search obj c
-  | Get (Safe, k) -> Map.get c k
-  | Get (Unsafe, k) -> Map.get_exn c k
+  | Get (Safe, k) -> PMap.get c k
+  | Get (Unsafe, k) -> PMap.get_exn c k
   | GroupBy (build,f) ->
       Coll.to_seq c
       |> CCSequence.map (fun x -> f x, x)
-      |> Map.multimap_of_seq ~build:(Map.make ~build ())
+      |> PMap.multimap_of_seq ~build:(PMap.make ~build ())
   | Contains (eq, x) -> Coll.contains ~eq x c
   | Count build ->
       Coll.to_seq c
-      |> Map.count_of_seq ~build:(Map.make ~build ())
+      |> PMap.count_of_seq ~build:(PMap.make ~build ())
+  | Lazy -> Lazy.force c
 
 let _do_binary : type a b c. (a, b, c) binary -> a -> b -> c
 = fun b c1 c2 -> match b with
@@ -565,7 +613,7 @@ let run_no_opt q = _run ~opt:false q
 
 (** {6 Basics on Collections} *)
 
-let map f q = Unary (Map f, q)
+let map f q = Unary (PMap f, q)
 
 let filter p q = Unary (Filter p, q)
 
@@ -581,10 +629,14 @@ let flat_map_seq f q =
   let f' x = Coll.of_seq (f x) in
   Unary (FlatMap f', q)
 
-let flat_map_list f q =
+let flat_map_l f q =
   let f' x = Coll.of_list (f x) in
   Unary (FlatMap f', q)
 
+let flatten q = Unary (FlatMap (fun x->x), q)
+
+let flatten_l q = Unary (FlatMap Coll.of_list, q)
+
 let take n q = Unary (Take n, q)
 
 let take_while p q = Unary (TakeWhile p, q)
@@ -594,26 +646,6 @@ let sort ?(cmp=Pervasives.compare) () q = Unary (Sort cmp, q)
 let distinct ?(cmp=Pervasives.compare) () q =
   Unary (Distinct cmp, q)
 
-let get key q =
-  Unary (Get (Safe, key), q)
-
-let get_exn key q =
-  Unary (Get (Unsafe, key), q)
-
-let map_iter q =
-  Unary (GeneralMap (fun m -> Coll.of_seq m.Map.to_seq), q)
-
-let map_iter_flatten q =
-  let f m = m.Map.to_seq
-      |> CCSequence.flatMap
-        (fun (k,v) -> Coll.to_seq v |> CCSequence.map (fun v' -> k,v'))
-      |> Coll.of_seq
-  in
-  Unary (GeneralMap f, q)
-
-let map_to_list q =
-  Unary (GeneralMap Map.to_list, q)
-
 (* choose a build method from the optional arguments *)
 let _make_build ?cmp ?eq ?hash () =
   let _maybe default o = match o with
@@ -623,23 +655,75 @@ let _make_build ?cmp ?eq ?hash () =
   match eq, hash with
   | Some _, _
   | _, Some _ ->
-      Map.FromHash ( _maybe (=) eq, _maybe Hashtbl.hash hash)
+      PMap.FromHash ( _maybe (=) eq, _maybe Hashtbl.hash hash)
   | _ ->
       match cmp with
-      | Some f -> Map.FromCmp f
-      | _ -> Map.Default
+      | Some f -> PMap.FromCmp f
+      | _ -> PMap.Default
+
+(** {6 Queries on PMaps} *)
+
+module M = struct
+  let get key q =
+    Unary (Get (Safe, key), q)
+
+  let get_exn key q =
+    Unary (Get (Unsafe, key), q)
+
+  let iter q =
+    Unary (GeneralMap (fun m -> Coll.of_seq m.PMap.to_seq), q)
+
+  let flatten q =
+    let f m = m.PMap.to_seq
+        |> CCSequence.flatMap
+          (fun (k,v) -> Coll.to_seq v |> CCSequence.map (fun v' -> k,v'))
+        |> Coll.of_seq
+    in
+    Unary (GeneralMap f, q)
+
+  let flatten' q =
+    let f m = m.PMap.to_seq
+        |> CCSequence.flatMap
+          (fun (k,v) -> CCSequence.of_list v |> CCSequence.map (fun v' -> k,v'))
+        |> Coll.of_seq
+    in
+    Unary (GeneralMap f, q)
+
+  let map f q =
+    Unary (GeneralMap (PMap.map f), q)
+
+  let to_list q =
+    Unary (GeneralMap PMap.to_list, q)
+
+  let reverse ?cmp ?eq ?hash () q =
+    let build = _make_build ?cmp ?eq ?hash () in
+    Unary (GeneralMap (PMap.reverse ~build), q)
+
+  let reverse_multimap  ?cmp ?eq ?hash () q =
+    let build = _make_build ?cmp ?eq ?hash () in
+    Unary (GeneralMap (PMap.reverse_multimap ~build), q)
+
+  let fold f acc q =
+    Unary (FoldMap (f, acc), q)
+
+  let fold_multimap f acc q =
+    let f' acc x l =
+      List.fold_left (fun acc y -> f acc x y) acc l
+    in
+    Unary (FoldMap (f', acc), q)
+end
 
 let group_by ?cmp ?eq ?hash f q =
   Unary (GroupBy (_make_build ?cmp ?eq ?hash (),f), q)
 
 let group_by' ?cmp ?eq ?hash f q =
-  map_iter (group_by ?cmp f q)
+  M.iter (group_by ?cmp f q)
 
 let count ?cmp ?eq ?hash () q =
   Unary (Count (_make_build ?cmp ?eq ?hash ()), q)
 
 let count' ?cmp () q =
-  map_iter (count ?cmp () q)
+  M.iter (count ?cmp () q)
 
 let fold f acc q =
   Unary (Fold (f, acc), q)
@@ -764,6 +848,10 @@ let (>>=) x f = Bind (f, x)
 
 let query_map f q = QueryMap (f, q)
 
+(** {6 Misc} *)
+
+let lazy_ q = Unary (Lazy, q)
+
 (** {6 Output containers} *)
 
 let to_list q =
@@ -787,3 +875,88 @@ let to_stack q =
 (** {6 Misc} *)
 
 let run_list q = run (q |> to_list)
+
+(** {6 Adapters} *)
+
+module AdaptSet(S : Set.S) = struct
+  let of_set set =
+    return (Coll.of_seq (fun k -> S.iter k set))
+
+  let to_set q =
+    let f c =
+      Coll.to_seq c |> CCSequence.fold (fun set x -> S.add x set) S.empty
+    in
+    query_map f q
+
+  let run q = run (q |> to_set)
+end
+
+module AdaptMap(M : Map.S) = struct
+  let _to_seq m k = M.iter (fun x y -> k (x,y)) m
+
+  let of_map map =
+    return (Coll.of_seq (_to_seq map))
+
+  let to_pmap m = {
+    PMap.get = (fun x -> try Some (M.find x m) with Not_found -> None);
+    PMap.size = (fun () -> M.cardinal m);
+    PMap.is_empty = (fun () -> M.is_empty m);
+    PMap.fold = (fun f acc -> M.fold (fun x y acc -> f acc x y) m acc);
+    PMap.to_seq = _to_seq m;
+  }
+
+  let to_map q =
+    let f c =
+      Coll.to_seq c
+      |> CCSequence.fold (fun m (x,y) -> M.add x y m) M.empty
+    in
+    query_map f q
+
+  let run q = run (q |> to_map)
+end
+
+module IO = struct
+  let slurp ic =
+    let l = lazy (
+      let buf_size = 256 in
+      let content = Buffer.create 120
+      and buf = String.make buf_size 'a' in
+      let rec next () =
+        let num = input ic buf 0 buf_size in
+        if num = 0
+          then Buffer.contents content (* EOF *)
+          else (Buffer.add_substring content buf 0 num; next ())
+      in next ()
+    ) in
+    lazy_ (return l)
+
+  (* find [c] in [s], starting at offset [i] *)
+  let rec _find s c i =
+    if i >= String.length s then None
+    else if s.[i] = c then Some i
+    else _find s c (i+1)
+
+  let rec _lines s i k = match _find s '\n' i with
+    | None -> ()
+    | Some j ->
+        let s' = String.sub s i (j-i) in
+        k s';
+        _lines s (j+1) k
+
+  let lines q =
+    (* sequence of lines *)
+    let f s = _lines s 0 |> Coll.of_seq in
+    query_map f q
+      
+  let lines' q =
+    let f s = lazy (_lines s 0 |> CCSequence.to_list) in
+    lazy_ (query_map f q)
+
+  let out oc q =
+    run q |> output_string oc
+
+  let out_lines oc q =
+    run q
+    |> Coll.to_seq
+    |> CCSequence.iter (fun l -> output_string oc l; output_char oc '\n')
+end
diff --git a/core/CCLinq.mli b/core/CCLinq.mli
index 347f5051..04e5266a 100644
--- a/core/CCLinq.mli
+++ b/core/CCLinq.mli
@@ -38,10 +38,10 @@ the order of execution.
 
 CCLinq.(
   start_list [1;2;3]
-  |> flat_map_list (fun x -> CCList.(x -- (x+10)))
+  |> flat_map_l (fun x -> CCList.(x -- (x+10)))
   |> sort ()
   |> count ()
-  |> map_to_list |> run
+  |> M.to_list |> run
 );;
 - : (int * int) list = [(13, 1); (12, 2); (11, 3); (10, 3); (9, 3);
     (8, 3); (7, 3); (6, 3); (5, 3); (4, 3); (3, 3); (2, 2); (1, 1)]
@@ -59,8 +59,8 @@ type 'a collection
     be used directly, they are to be processed using a query (type {!'a t})
     and converted to some list/sequence/array *)
 
-(** {2 A polymorphic map} *)
-module Map : sig
+(** {2 Polymorphic Maps} *)
+module PMap : sig
   type ('a, 'b) t
 
   val get : ('a,'b) t -> 'a -> 'b option
@@ -74,6 +74,8 @@ module Map : sig
   val to_seq : ('a, 'b) t -> ('a * 'b) sequence
 
   val to_list : ('a, 'b) t -> ('a * 'b) list
+
+  val to_coll : ('a, 'b) t -> ('a * 'b) collection
 end
 
 (** {2 Query operators} *)
@@ -86,16 +88,24 @@ type 'a t
 val start : 'a -> 'a t
 (** Start with a single value *)
 
-val start_list : 'a list -> 'a collection t
+val of_list : 'a list -> 'a collection t
 (** Query that just returns the elements of the list *)
 
-val start_array : 'a array -> 'a collection t
+val of_array : 'a array -> 'a collection t
+val of_array_i : 'a array -> (int * 'a) collection t
 
-val start_hashtbl : ('a,'b) Hashtbl.t -> ('a * 'b) collection t
+val of_hashtbl : ('a,'b) Hashtbl.t -> ('a * 'b) collection t
 
-val start_seq : 'a sequence -> 'a collection t
+val of_seq : 'a sequence -> 'a collection t
 (** Query that returns the elements of the given sequence. *)
 
+val of_queue : 'a Queue.t -> 'a collection t
+
+val of_stack : 'a Stack.t -> 'a collection t
+
+val of_string : string -> char collection t
+(** Traverse the characters of the string *)
+
 (** {6 Execution} *)
 
 val run : 'a t -> 'a
@@ -132,7 +142,11 @@ val flat_map : ('a -> 'b collection) -> 'a collection t -> 'b collection t
 val flat_map_seq : ('a -> 'b sequence) -> 'a collection t -> 'b collection t
 (** Same as {!flat_map} but using sequences *)
 
-val flat_map_list : ('a -> 'b list) -> 'a collection t -> 'b collection t
+val flat_map_l : ('a -> 'b list) -> 'a collection t -> 'b collection t
+
+val flatten : 'a collection collection t -> 'a collection t
+
+val flatten_l : 'a list collection t -> 'a collection t
 
 val take : int -> 'a collection t -> 'a collection t
 (** take at most [n] elements *)
@@ -147,27 +161,50 @@ val distinct : ?cmp:'a ord -> unit -> 'a collection t -> 'a collection t
 (** Remove duplicate elements from the input collection.
     All elements in the result are distinct. *)
 
-(** {6 Maps} *)
+(** {6 Queries on Maps} *)
 
-val get : 'a -> ('a, 'b) Map.t t -> 'b option t
-(** Select a key from a map *)
+module M : sig
+  val get : 'a -> ('a, 'b) PMap.t t -> 'b option t
+  (** Select a key from a map *)
 
-val get_exn : 'a -> ('a, 'b) Map.t t -> 'b t
-(** Unsafe version of {!get}.
-    @raise Not_found if the key is not present. *)
+  val get_exn : 'a -> ('a, 'b) PMap.t t -> 'b t
+  (** Unsafe version of {!get}.
+      @raise Not_found if the key is not present. *)
 
-val map_iter : ('a,'b) Map.t t -> ('a*'b) collection t
-(** View a multimap as a proper collection *)
+  val iter : ('a,'b) PMap.t t -> ('a*'b) collection t
+  (** View a multimap as a proper collection *)
 
-val map_iter_flatten : ('a,'b collection) Map.t t -> ('a*'b) collection t
-(** View a multimap as a collection of individual key/value pairs *)
+  val flatten : ('a,'b collection) PMap.t t -> ('a*'b) collection t
+  (** View a multimap as a collection of individual key/value pairs *)
 
-val map_to_list : ('a,'b) Map.t t -> ('a*'b) list t
+  val flatten' : ('a,'b list) PMap.t t -> ('a*'b) collection t
+  (** View a multimap as a collection of individual key/value pairs *)
+
+  val map : ('b -> 'c) -> ('a, 'b) PMap.t t -> ('a, 'c) PMap.t t
+  (** Transform values *)
+
+  val to_list : ('a,'b) PMap.t t -> ('a*'b) list t
+
+  val reverse : ?cmp:'b ord -> ?eq:'b equal -> ?hash:'b hash -> unit ->
+                ('a,'b) PMap.t t -> ('b,'a list) PMap.t t
+  (** Reverse relation of the map, as a multimap *)
+
+  val reverse_multimap : ?cmp:'b ord -> ?eq:'b equal -> ?hash:'b hash -> unit ->
+                          ('a,'b list) PMap.t t -> ('b,'a list) PMap.t t
+  (** Reverse relation of the multimap *)
+
+  val fold : ('acc -> 'a -> 'b -> 'acc) -> 'acc -> ('a,'b) PMap.t t -> 'acc t
+  (** Fold on the items of the map *)
+
+  val fold_multimap : ('acc -> 'a -> 'b -> 'acc) -> 'acc ->
+                      ('a,'b list) PMap.t t -> 'acc t
+  (** Fold on the items of the multimap *)
+end
 
 (** {6 Aggregation} *)
 
 val group_by : ?cmp:'b ord -> ?eq:'b equal -> ?hash:'b hash ->
-               ('a -> 'b) -> 'a collection t -> ('b,'a list) Map.t t
+               ('a -> 'b) -> 'a collection t -> ('b,'a list) PMap.t t
 (** [group_by f] takes a collection [c] as input, and returns
     a multimap [m] such that for each [x] in [c],
     [x] occurs in [m] under the key [f x]. In other words, [f] is used
@@ -177,7 +214,7 @@ val group_by' : ?cmp:'b ord -> ?eq:'b equal -> ?hash:'b hash ->
                 ('a -> 'b) -> 'a collection t -> ('b * 'a list) collection t
 
 val count : ?cmp:'a ord -> ?eq:'a equal -> ?hash:'a hash ->
-             unit -> 'a collection t -> ('a, int) Map.t t
+             unit -> 'a collection t -> ('a, int) PMap.t t
 (** [count c] returns a map from elements of [c] to the number
     of time those elements occur. *)
 
@@ -189,7 +226,8 @@ val fold : ('b -> 'a -> 'b) -> 'b -> 'a collection t -> 'b t
 val size : _ collection t -> int t
 (** Count how many elements the collection contains *)
 
-val reduce : ('a -> 'b) -> ('a -> 'b -> 'b) -> ('b -> 'c) -> 'a collection t -> 'c option t
+val reduce : ('a -> 'b) -> ('a -> 'b -> 'b) -> ('b -> 'c) ->
+             'a collection t -> 'c option t
 (** [reduce start mix stop q] uses [start] on the first element of [q],
     and combine the result with following elements using [mix]. The final
     value is transformed using [stop]. This returns [None] if the collection
@@ -234,7 +272,7 @@ val join : ?cmp:'key ord -> ?eq:'key equal -> ?hash:'key hash ->
 
 val group_join : ?cmp:'a ord -> ?eq:'a equal -> ?hash:'a hash ->
                   ('b -> 'a) -> 'a collection t -> 'b collection t ->
-                  ('a, 'b list) Map.t t
+                  ('a, 'b list) PMap.t t
 (** [group_join key2] associates to every element [x] of
     the first collection, all the elements [y] of the second
     collection such that [eq x (key y)] *)
@@ -293,7 +331,11 @@ val return : 'a -> 'a t
 (** Synonym to {!start} *)
 
 val query_map : ('a -> 'b) -> 'a t -> 'b t
-(** Map results directly, rather than collections of elements *)
+(** PMap results directly, rather than collections of elements *)
+
+(** {6 Misc} *)
+
+val lazy_ : 'a lazy_t t -> 'a t
 
 (** {6 Output Containers} *)
 
@@ -313,3 +355,33 @@ val to_hashtbl : ('a * 'b) collection t -> ('a, 'b) Hashtbl.t t
 val to_queue : 'a collection t -> ('a Queue.t -> unit) t
 
 val to_stack : 'a collection t -> ('a Stack.t -> unit) t
+
+(** {6 Adapters} *)
+
+module AdaptSet(S : Set.S) : sig
+  val of_set : S.t -> S.elt collection t
+  val to_set : S.elt collection t -> S.t t
+  val run : S.elt collection t -> S.t
+end
+
+module AdaptMap(M : Map.S) : sig
+  val of_map : 'a M.t -> (M.key * 'a) collection t
+  val to_pmap : 'a M.t -> (M.key, 'a) PMap.t
+  val to_map : (M.key * 'a) collection t -> 'a M.t t
+  val run : (M.key * 'a) collection t -> 'a M.t
+end
+
+module IO : sig
+  val slurp : in_channel -> string t
+  (** Slurp the whole channel in (blocking), returning the corresponding string *)
+
+  val lines : string t -> string collection t
+  (** Convert a string into a collection of lines *)
+
+  val lines' : string t -> string list t
+  (** Convert a string into a list of lines *)
+
+  val out : out_channel -> string t -> unit
+  val out_lines : out_channel -> string collection t -> unit
+  (** Evaluate the query and print it line by line on the output *)
+end