Canonically renaming fold_map into fold_left_map in library Option.

Also adding fold_right_map by consistency.

2 files changed, 16 insertions, 3 deletions

diff --git a/lib/option.ml b/lib/option.ml
index 7cedffef0..98b168035 100644
--- a/lib/option.ml
+++ b/lib/option.ml
@@ -121,12 +121,19 @@ let fold_right f x a =
   | Some y -> f y a
   | _ -> a
 
-(** [fold_map f a x] is [a, f y] if [x] is [Some y], and [a] otherwise. *)
-let fold_map f a x =
+(** [fold_left_map f a x] is [a, f y] if [x] is [Some y], and [a] otherwise. *)
+let fold_left_map f a x =
   match x with
   | Some y -> let a, z = f a y in a, Some z
   | _ -> a, None
 
+let fold_right_map f x a =
+  match x with
+  | Some y -> let z, a = f y a in Some z, a
+  | _ -> None, a
+
+let fold_map = fold_left_map
+
 (** [cata f a x] is [a] if [x] is [None] and [f y] if [x] is [Some y]. *)
 let cata f a = function
   | Some c -> f c
diff --git a/lib/option.mli b/lib/option.mli
index c4d1ebc3a..66f05023f 100644
--- a/lib/option.mli
+++ b/lib/option.mli
@@ -85,7 +85,13 @@ val fold_left2 : ('a -> 'b -> 'c -> 'a) -> 'a -> 'b option -> 'c option -> 'a
 (** [fold_right f x a] is [f y a] if [x] is [Some y], and [a] otherwise. *)
 val fold_right : ('a -> 'b -> 'b) -> 'a option -> 'b -> 'b
 
-(** [fold_map f a x] is [a, f y] if [x] is [Some y], and [a] otherwise. *)
+(** [fold_left_map f a x] is [a, f y] if [x] is [Some y], and [a] otherwise. *)
+val fold_left_map : ('a -> 'b -> 'a * 'c) -> 'a -> 'b option -> 'a * 'c option
+
+(** Same as [fold_left_map] on the right *)
+val fold_right_map : ('b -> 'a -> 'c * 'a) -> 'b option -> 'a -> 'c option * 'a
+
+(** @deprecated Same as [fold_left_map] *)
 val fold_map : ('a -> 'b -> 'a * 'c) -> 'a -> 'b option -> 'a * 'c option
 
 (** [cata f e x] is [e] if [x] is [None] and [f a] if [x] is [Some a] *)