With a couple of function pointers you can climb precedence with just functions:

  parse_left_to_right(with(), is_token()) {
    left = with()
    while(is_token()) {
      right = with()
      left = operate(left, right, operator)
    }
    ret left;
  }

  p0() { ret lex digit or ident; };
  p1() { ret parse_left_right(p0, is_mul); };
  p2() { ret parse_left_right(p1, is_add); };

... and so on for all operators