creation of the empty sequence

sequence.ml

@@ -31,6 +31,8 @@ type 'a t = ('a -> unit) -> unit
 (** Build a sequence from a iter function *)
 let from_iter f = f
 
+let empty = fun k -> ()
+
 let singleton x = fun k -> k x
 
 (** Infinite sequence of the same element *)

sequence.mli

@@ -36,6 +36,9 @@ type +'a t
 val from_iter : (('a -> unit) -> unit) -> 'a t
   (** Build a sequence from a iter function *)
 
+val empty : 'a t
+  (** Empty sequence *)
+
 val singleton : 'a -> 'a t
   (** Singleton sequence *)