modules to convert lists and hashtables from/to sequences

sequence.ml

@@ -49,3 +49,20 @@ let drop n seq =
   let seq_fun k = seq.seq_fun
     (fun x -> if !count >= n then k x else incr count)
   in { seq_fun; }
+
+module List =
+  struct
+    let of_seq seq = List.rev (fold (fun y x -> x::y) [] seq)
+    let to_seq l = from_iter (fun k -> List.iter k l)
+  end
+
+module Hashtbl =
+  struct
+    let of_seq seq =
+      let h = Hashtbl.create 3 in
+      iter (fun (k,v) -> Hashtbl.replace h k v) seq;
+      h
+    let to_seq h =
+      from_iter (fun k -> Hashtbl.iter (fun a b -> k (a, b)) h)
+  end
+

sequence.mli

@@ -31,3 +31,17 @@ val take : int -> 'a sequence -> 'a sequence
 
 val drop : int -> 'a sequence -> 'a sequence
   (** Drop the [n] first elements of the sequence *)
+
+(** {2 Basic data structures converters} *)
+
+module List :
+  sig
+    val of_seq : 'a sequence -> 'a list
+    val to_seq : 'a list -> 'a sequence
+  end
+
+module Hashtbl :
+  sig
+    val of_seq : ('a * 'b) sequence -> ('a, 'b) Hashtbl.t
+    val to_seq : ('a, 'b) Hashtbl.t -> ('a * 'b) sequence
+  end

tests.ml

@@ -1,18 +1,6 @@
 
 (** {2 Test sequences} *)
 
-let seq_of_list l = Sequence.from_iter (fun k -> List.iter k l)
-
-let list_of_seq seq = List.rev (Sequence.fold (fun y x -> x::y) [] seq)
-
-let seq_of_hashtbl h =
-  Sequence.from_iter (fun k -> Hashtbl.iter (fun a b -> k (a, b)) h)
-
-let hashtbl_from_seq seq =
-  let h = Hashtbl.create 3 in
-  Sequence.iter (fun (k,v) -> Hashtbl.replace h k v) seq;
-  h
-
 (** print a list of items using the printing function *)
 let rec pp_list ?(sep=", ") pp_item formatter = function
   | x::y::xs -> Format.fprintf formatter "%a%s@,%a"
@@ -22,8 +10,10 @@ let rec pp_list ?(sep=", ") pp_item formatter = function
 
 let _ =
   let l = [0;1;2;3;4;5;6] in
-  let l' = list_of_seq (Sequence.filter (fun x -> x mod 2 = 0) (seq_of_list l)) in
+  let l' = Sequence.List.of_seq
-  let l'' = list_of_seq (Sequence.take 3 (Sequence.drop 1 (seq_of_list l))) in
+    (Sequence.filter (fun x -> x mod 2 = 0) (Sequence.List.to_seq l)) in
+  let l'' = Sequence.List.of_seq
+    (Sequence.take 3 (Sequence.drop 1 (Sequence.List.to_seq l))) in
   Format.printf "l=@[<h>[%a]@]@." (pp_list Format.pp_print_int) l;
   Format.printf "l'=@[<h>[%a]@]@." (pp_list Format.pp_print_int) l';
   Format.printf "l''=@[<h>[%a]@]@." (pp_list Format.pp_print_int) l'';