offer two different functions for combining Map and Seq. Both build

an extended version of Map, with additional conversion functions relative to Sequence.
One can Adapt an already existing Map module, or Make an extended Map directly

sequence.ml

@@ -228,25 +228,39 @@ let to_set (type s) (type v) m seq =
     (fun set x -> S.add x set)
     S.empty seq
 
-(** Iterate on maps. The functor must be instantiated with a map type *)
-module Map(M : Map.S) =
-  struct
-    type 'a map = 'a M.t
-    type key = M.key
-    
-    let to_seq m =
-      from_iter (fun k -> M.iter (fun key value -> k (key, value)) m)
-
-    let keys m =
-      from_iter (fun k -> M.iter (fun key _ -> k key) m)
-
-    let values m =
-      from_iter (fun k -> M.iter (fun _ value -> k value) m)
-
-    let of_seq seq =
-      fold (fun m (key,value) -> M.add key value m) M.empty seq
+(** Conversion between maps and sequences. *)
+module Map = struct
+  module type S = sig
+    type +'a map
+    include Map.S with type 'a t := 'a map
+    val to_seq : 'a map -> (key * 'a) t
+    val of_seq : (key * 'a) t -> 'a map
+    val keys : 'a map -> key t
+    val values : 'a map -> 'a t
   end
 
+  (** Adapt a pre-existing Map module to make it sequence-aware *)
+  module Adapt(M : Map.S) : S with type key = M.key and type 'a map = 'a M.t = struct
+    type 'a map = 'a M.t
+
+    let to_seq m = from_iter (fun k -> M.iter (fun x y -> k (x,y)) m)
+
+    let of_seq seq = fold (fun m (k,v) -> M.add k v m) M.empty seq
+
+    let keys m = from_iter (fun k -> M.iter (fun x _ -> k x) m)
+
+    let values m = from_iter (fun k -> M.iter (fun _ y -> k y) m)
+
+    include M
+  end
+
+  (** Create an enriched Map module, with sequence-aware functions *)
+  module Make(V : Map.OrderedType) : S with type key = V.t = struct
+    module M = Map.Make(V)
+    include Adapt(M)
+  end
+end
+
 (** {2 Pretty printing of sequences} *)
 
 (** Pretty print a sequence of ['a], using the given pretty printer

sequence.mli

@@ -151,21 +151,24 @@ 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 *)
 
-(** Iterate on maps. The functor must be instantiated with a map type *)
-module Map(M : Map.S) :
-  sig
-    type 'a map = 'a M.t
-    type key = M.key
-    
+(** Conversion between maps and sequences. *)
+module Map : sig
+  module type S = sig
+    type +'a map
+    include Map.S with type 'a t := 'a map
     val to_seq : 'a map -> (key * 'a) t
-
-    val keys : 'a map -> key t
-
-    val values : 'a map -> 'a t
-
     val of_seq : (key * 'a) t -> 'a map
+    val keys : 'a map -> key t
+    val values : 'a map -> 'a t
   end
 
+  (** Adapt a pre-existing Map module to make it sequence-aware *)
+  module Adapt(M : Map.S) : S with type key = M.key and type 'a map = 'a M.t
+
+  (** Create an enriched Map module, with sequence-aware functions *)
+  module Make(V : Map.OrderedType) : S with type key = V.t
+end
+
 (** {2 Pretty printing of sequences} *)
 
 val pp_seq : ?sep:string -> (Format.formatter -> 'a -> unit) ->

tests.ml

@@ -9,9 +9,15 @@ let pp_list ?(sep=", ") pp_item formatter l =
 module ISet = Set.Make(struct type t = int let compare = compare end)
 let iset = (module ISet : Set.S with type elt = int and type t = ISet.t)
 
+module OrderedString = struct type t = string let compare = compare end
+module SMap = Sequence.Map.Make(OrderedString)
+
+let my_map = SMap.of_seq (Sequence.of_list ["1", 1; "2", 2; "3", 3; "answer", 42])
+
 let sexpr = "(foo bar (bazz quux hello 42) world (zoo foo bar (1 2 (3 4))))"
 
 let _ =
+  (* lists *)
   let l = [0;1;2;3;4;5;6] in
   let l' = Sequence.to_list
     (Sequence.filter (fun x -> x mod 2 = 0) (Sequence.of_list l)) in
@@ -39,11 +45,21 @@ let _ =
     (Sequence.of_array
       (Sequence.to_array (Sequence.append
         (Sequence.take 5 (Sequence.of_list l3)) (Sequence.of_list l4))));
+  (* maps *)
+  Format.printf "@[<h>map: %a@]@."
+    (Sequence.pp_seq (fun formatter (k,v) -> Format.fprintf formatter "\"%s\" -> %d" k v))
+    (SMap.to_seq my_map);
+  let module MyMapSeq = Sequence.Map.Adapt(Map.Make(OrderedString)) in
+  let my_map' = MyMapSeq.of_seq (Sequence.of_list ["1", 1; "2", 2; "3", 3; "answer", 42]) in
+  Format.printf "@[<h>map: %a@]@."
+    (Sequence.pp_seq (fun formatter (k,v) -> Format.fprintf formatter "\"%s\" -> %d" k v))
+    (MyMapSeq.to_seq my_map');
   (* sum *)
   let n = 100000000 in
   let sum = Sequence.fold (+) 0 (Sequence.take n (Sequence.repeat 1)) in
   Format.printf "%dx1 = %d@." n sum;
   assert (n=sum);
+  (* sexpr *)
   let s = Sexpr.of_seq (Sexpr.lex (Sequence.of_str sexpr)) in
   let s = Sexpr.of_seq (Sequence.map
     (function | `Atom s -> `Atom (String.capitalize s) | tok -> tok)