Lists: add map_filter

src/util/lists.ml

@@ -28,6 +28,11 @@ let map_fold_right f l acc =
     (fun e (l, acc) -> let e, acc = f e acc in e :: l, acc)
     l ([], acc)
 
+let map_filter f l =
+  List.fold_right
+    (fun e l -> match f e with Some e -> e :: l | None -> l)
+    l []
+
 let equal pr l1 l2 =
   try List.for_all2 pr l1 l2 with Invalid_argument _ -> false
 

src/util/lists.mli

@@ -20,6 +20,8 @@ val map_fold_left :
 val map_fold_right :
   ('a -> 'acc -> 'b * 'acc) -> 'a list -> 'acc -> 'b list * 'acc
 
+val map_filter : ('a -> 'b option) -> 'a list -> 'b list
+
 val equal : ('a -> 'b -> bool) -> 'a list -> 'b list -> bool
 
 val compare : ('a -> 'a -> int) -> 'a list -> 'a list -> int