add CCList.{find_pred,find_pred_exn}

src/core/CCList.ml

@@ -385,6 +385,22 @@ let last n l =
   let len = List.length l in
   if len < n then l else drop (len-n) l
 
+let rec find_pred p l = match l with
+  | [] -> None
+  | x :: _ when p x -> Some x
+  | _ :: tl -> find_pred p tl
+
+let find_pred_exn p l = match find_pred p l with
+  | None -> raise Not_found
+  | Some x -> x
+
+(*$T
+  find_pred ((=) 4) [1;2;5;4;3;0] = Some 4
+  find_pred (fun _ -> true) [] = None
+  find_pred (fun _ -> false) (1 -- 10) = None
+  find_pred (fun x -> x < 10) (1 -- 9) = Some 1
+*)
+
 let findi f l =
   let rec aux f i = function
     | [] -> None

src/core/CCList.mli

@@ -109,6 +109,16 @@ 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_pred : ('a -> bool) -> 'a t -> 'a option
+(** [find_pred p l] finds the first element of [l] that satisfies [p],
+    or returns [None] if no element satisfies [p]
+    @since NEXT_RELEASE *)
+
+val find_pred_exn : ('a -> bool) -> 'a t -> 'a
+(** Unsafe version of {!find_pred}
+    @raise Not_found if no such element is found
+    @since NEXT_RELEASE *)
+
 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