Bad Ocaml

(* Counts the number of instances of num in x::xs
 * for instance, (countNum ([1;1;2;3], 0, 1)) should return 2*)

let rec countNum (lst, soFar, num) =
   match lst with
      | []  -> soFar
      | num::xs -> countNum (xs, (soFar+1), num)
      | _::xs   -> countNum (xs, soFar, num);;

(* With this implementation the above example returns 4 *)