first.ml

let first p xs =
  let length = Array.length xs in
  (* mutable aray index *)
  let i = ref 0 in
  (* there are no loop breaks in OCaml anyway *)
  let break = ref false in
  while not (!break) && !i < length do 
    if p (xs.(!i)) then break := true else i := (!i) + 1
  done;
  !i