fmap function

sequence.ml

@@ -129,6 +129,13 @@ let flatMap f seq =
   from_iter
     (fun k -> seq (fun x -> (f x) k))
 
+let fmap f seq =
+  from_iter
+    (fun k ->
+      seq (fun x -> match f x with
+          | None -> ()
+          | Some y -> k y))
+
 (** Insert the given element between every element of the sequence *)
 let intersperse elem seq =
   fun k ->

sequence.mli

@@ -125,6 +125,9 @@ val flatMap : ('a -> 'b t) -> 'a t -> 'b t
   (** Monadic bind. It applies the function to every element of the
       initial sequence, and calls [concat]. *)
 
+val fmap : ('a -> 'b option) -> 'a t -> 'b t
+  (** Specialized version of {!flatMap} for options.  *)
+
 val intersperse : 'a -> 'a t -> 'a t
   (** Insert the second element between every element of the sequence *)