diff --git a/core/CCPair.ml b/core/CCPair.ml
index 136bc567..fa15d4c9 100644
--- a/core/CCPair.ml
+++ b/core/CCPair.ml
@@ -36,6 +36,11 @@ let map f g (x,y) = f x, g y
 
 let map_same f (x,y) = f x, f y
 
+let map_fst f (x,_) = f x
+let map_snd f (_,x) = f x
+
+let iter f (x,y) = f x y
+
 let swap (x,y) = y, x
 
 let (<<<) = map1
@@ -47,6 +52,10 @@ let ( *** ) = map
 let ( &&& ) f g x = f x, g x
 
 let merge f (x,y) = f x y
+let fold = merge
+
+let dup x = x,x
+let dup_map f x = x, f x
 
 let equal f g (x1,y1) (x2,y2) = f x1 x2 && g y1 y2
 
diff --git a/core/CCPair.mli b/core/CCPair.mli
index 45748dab..ba532242 100644
--- a/core/CCPair.mli
+++ b/core/CCPair.mli
@@ -36,6 +36,16 @@ val map : ('a -> 'c) -> ('b -> 'd) -> ('a * 'b) -> ('c * 'd)
 
 val map_same : ('a -> 'b) -> ('a*'a) -> ('b*'b)
 
+val map_fst : ('a -> 'b) -> ('a * _) -> 'b
+(** Compose the given function with [fst].
+    @since NEXT_RELEASE *)
+
+val map_snd : ('a -> 'b) -> (_ * 'a) -> 'b
+(** Compose the given function with [snd].
+    @since NEXT_RELEASE *)
+
+val iter : ('a -> 'b -> unit) -> ('a * 'b) -> unit
+
 val swap : ('a * 'b) -> ('b * 'a)
 (** Swap the components of the tuple *)
 
@@ -55,6 +65,19 @@ val ( &&& ) : ('a -> 'b) -> ('a -> 'c) -> 'a -> ('b * 'c)
 val merge : ('a -> 'b -> 'c) -> ('a * 'b) -> 'c
 (** Uncurrying (merges the two components of a tuple) *)
 
+val fold : ('a -> 'b -> 'c) -> ('a * 'b) -> 'c
+(** Synonym to {!merge}
+    @since NEXT_RELEASE *)
+
+val dup : 'a -> ('a * 'a)
+(** [dup x = (x,x)] (duplicate the value)
+    @since NEXT_RELEASE *)
+
+val dup_map : ('a -> 'b) -> 'a -> ('a * 'b)
+(** [dup_map f x = (x, f x)]. Duplicates the value and applies the function
+    to the second copy.
+    @since NEXT_RELEASE *)
+
 val equal : ('a -> 'a -> bool) -> ('b -> 'b -> bool) -> ('a * 'b) -> ('a * 'b) -> bool
 
 val compare : ('a -> 'a -> int) -> ('b -> 'b -> int) -> ('a * 'b) -> ('a * 'b) -> int