adding find_map_opt utility function

Reviewed By: jvillard

Differential Revision: D3316364

fbshipit-source-id: 9bd5153

infer/src/backend/iList.ml

@@ -175,6 +175,15 @@ let map2 f l1 l2 =
     | _ -> raise Fail in
   go l1 l2 []
 
+(** Return the first non-None result found when applying f to elements of l *)
+let rec find_map_opt f = function
+  | [] -> None
+  | e :: l' ->
+      let e' = f e in
+      if e' <> None
+      then e'
+      else find_map_opt f l'
+
 let to_string f l =
   let rec aux l =
     match l with

infer/src/backend/iList.mli

@@ -97,4 +97,7 @@ exception Fail
 (** Apply [f] to pairs of elements; raise [Fail] if the two lists have different lenghts. *)
 val map2 : ('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list
 
+(** Return the first non-None result found when applying f to elements of l *)
+val find_map_opt : ('a -> 'b option) -> 'a list -> 'b option
+
 val to_string : ('a -> string) -> 'a list -> string