in ocaml language

Write a function cond_dup : a list -> ('a -> bool) -> 'a list that takes in a list and a preciate and duplicates all elements which satisfy the condition expressed in the predicate. For example, cond_dup [3;4;5] (fun 1) [3;3; 4; 5;5] . X -> x mod 2 = = let rec cond_dup 1 f = (* YOUR CODE HERE *)