merge from master

core/CCList.ml

@@ -219,13 +219,25 @@ let last n l =
   let len = List.length l in
   if len < n then l else drop (len-n) l
 
-let find p l =
+let find_idx p l =
   let rec search i l = match l with
   | [] -> None
   | x::_ when p x -> Some (i, x)
   | _::xs -> search (i+1) xs
   in search 0 l
 
+let rec find f l = match l with
+  | [] -> None
+  | x::l' ->
+      match f x with
+      | Some _ as res -> res
+      | None -> find f l'
+
+(*$T
+  find (fun x -> if x=3 then Some "a" else None) [1;2;3;4] = Some "a"
+  find (fun x -> if x=3 then Some "a" else None) [1;2;4;5] = None
+*)
+
 let filter_map f l =
   let rec recurse acc l = match l with
   | [] -> List.rev acc

core/CCList.mli

@@ -86,10 +86,15 @@ val last : int -> 'a t -> 'a t
 (** [last n l] takes the last [n] elements of [l] (or less if
     [l] doesn't have that many elements *)
 
-val find : ('a -> bool) -> 'a t -> (int * 'a) option
+val find_idx : ('a -> bool) -> 'a t -> (int * 'a) option
 (** [find p x] returns [Some (i,x)] where [x] is the [i]-th element of [l],
     and [p x] holds. Otherwise returns [None] *)
 
+val find : ('a -> 'b option) -> 'a t -> 'b option
+(** [find f l] traverses [l], applying [f] to each element. If for
+    some element [x], [f x = Some y], then [Some y] is returned. Otherwise
+    the call returns [None] *)
+
 val filter_map : ('a -> 'b option) -> 'a t -> 'b t
 (** Map and remove elements at the same time *)