diff --git a/enum.ml b/enum.ml
index 58e94068..8a72da94 100644
--- a/enum.ml
+++ b/enum.ml
@@ -289,7 +289,7 @@ let zipIndex enum =
 (** {2 Complex combinators} *)
 
 (** Pick elements fairly in each sub-enum *)
-let round_robin enum =
+let merge enum =
   (* list of sub-enums *)
   let l = fold (fun acc x -> x::acc) [] enum in
   let l = List.rev l in
@@ -309,6 +309,11 @@ let round_robin enum =
             x
     in next
 
+(** Assuming subsequences are sorted in increasing order, merge them
+    into an increasing sequence *)
+let merge_sorted ?(cmp=compare) enum =
+  failwith "not implemented"
+
 (** {3 Mutable double-linked list, similar to {! Deque.t} *)
 module MList = struct
   type 'a t = 'a node option ref
@@ -362,7 +367,7 @@ let persistent gen =
   (* done recursing through the generator *)
   MList.to_enum l
 
-let tee ?(n=2) enum =
+let round_robin ?(n=2) enum =
   fun () ->
     (* array of queues, together with their index *)
     let qs = Array.init n (fun i -> Queue.create ()) in
@@ -399,7 +404,7 @@ let tee ?(n=2) enum =
 (** Duplicate the enum into [n] generators (default 2). The generators
     share the same underlying instance of the enum, so the optimal case is
     when they are consumed evenly *)
-let dup ?(n=2) enum =
+let tee ?(n=2) enum =
   fun () ->
     (* array of queues, together with their index *)
     let qs = Array.init n (fun i -> Queue.create ()) in
diff --git a/enum.mli b/enum.mli
index 66ff9bb9..db87070e 100644
--- a/enum.mli
+++ b/enum.mli
@@ -139,20 +139,24 @@ val zipIndex : 'a t -> (int * 'a) t
 
 (** {2 Complex combinators} *)
 
-val round_robin : 'a t t -> 'a t
+val merge : 'a t t -> 'a t
   (** Pick elements fairly in each sub-enum. The given enum
       must be finite (not its elements, though). *)
 
+val merge_sorted : ?cmp:('a -> 'a -> int) -> 'a t t -> 'a t
+  (** Assuming subsequences are sorted in increasing order, merge them
+      into an increasing sequence *)
+
 val persistent : 'a generator -> 'a t
   (** Store content of the generator in memory, to be able to iterate on it
       several times later *)
 
-val tee : ?n:int -> 'a t -> 'a generator t
+val round_robin : ?n:int -> 'a t -> 'a generator t
   (** Split the enum into [n] generators in a fair way. Elements with
       [index = k mod n] with go to the k-th enum. [n] defaults value
       is 2. *)
 
-val dup : ?n:int -> 'a t -> 'a generator t
+val tee : ?n:int -> 'a t -> 'a generator t
   (** Duplicate the enum into [n] generators (default 2). The generators
       share the same underlying instance of the enum, so the optimal case is
       when they are consumed evenly *)
diff --git a/tests/test_enum.ml b/tests/test_enum.ml
index cdedd461..064359f1 100644
--- a/tests/test_enum.ml
+++ b/tests/test_enum.ml
@@ -51,9 +51,9 @@ let test_filterMap () =
   OUnit.assert_equal ["2"; "4"; "6"; "8"; "10"] (Enum.to_list e);
   ()
 
-let test_round_robin () =
+let test_merge () =
   let e = Enum.of_list [1--3; 4--6; 7--9] in
-  let e' = Enum.round_robin e in
+  let e' = Enum.merge e in
   OUnit.assert_equal [1;4;7;2;5;8;3;6;9] (Enum.to_list e');
   ()
 
@@ -69,8 +69,8 @@ let test_persistent () =
   OUnit.assert_equal [0;1;2;3;4;5] (Enum.to_list e);
   ()
 
-let test_tee () =
-  let e = Enum.tee ~n:2 (1--10) in
+let test_round_robin () =
+  let e = Enum.round_robin ~n:2 (1--10) in
   let e = Enum.map Enum.persistent e in
   let l = Enum.to_list e in
   match l with
@@ -79,8 +79,8 @@ let test_tee () =
     OUnit.assert_equal [2;4;6;8;10] (Enum.to_list b)
   | _ -> OUnit.assert_failure "wrong list lenght"
 
-let test_strong_tee () =
-  let e = Enum.tee ~n:3 (1 -- 999) in
+let test_big_rr () =
+  let e = Enum.round_robin ~n:3 (1 -- 999) in
   let l = Enum.to_list e in
   let l' = List.map Enum.Gen.length l in
   OUnit.assert_equal [333;333;333] l';
@@ -113,10 +113,10 @@ let suite =
       "test_flatMap" >:: test_flatMap;
       "test_zip" >:: test_zip;
       "test_filterMap" >:: test_filterMap;
-      "test_round_robin" >:: test_round_robin;
+      "test_merge" >:: test_merge;
       "test_persistent" >:: test_persistent;
-      "test_tee" >:: test_tee;
-      "test_strong_tee" >:: test_strong_tee;
+      "test_round_robin" >:: test_round_robin;
+      "test_big_rr" >:: test_big_rr;
       "test_interleave" >:: test_interleave;
       "test_intersperse" >:: test_intersperse;
       "test_product" >:: test_product;