diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/option.ml | 6 | ||||
| -rw-r--r-- | lib/option.mli | 3 |
2 files changed, 9 insertions, 0 deletions
diff --git a/lib/option.ml b/lib/option.ml index 2a530b89bd..942fff48ae 100644 --- a/lib/option.ml +++ b/lib/option.ml @@ -97,6 +97,12 @@ 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 = + match x with + | Some y -> let a, z = f a y in a, Some z + | _ -> a, None + (** [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 8002a7ea29..ef2e311a62 100644 --- a/lib/option.mli +++ b/lib/option.mli @@ -66,6 +66,9 @@ 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. *) +val fold_map : ('a -> 'b -> 'a * 'c) -> 'a -> 'b option -> 'a * 'c option + (** [cata e f x] is [e] if [x] is [None] and [f a] if [x] is [Some a] *) val cata : ('a -> 'b) -> 'b -> 'a option -> 'b |