* @param expression
   * @return Stella_Object
   */
  public static Stella_Object onlyIf(Stella_Object test, Stella_Object expression) {
    return (Cons.list$(Cons.cons(Stella.SYM_STELLA_CHOOSE, Cons.cons(test, Cons.cons(Cons.cons(expression, Cons.cons(Stella.SYM_STELLA_NULL, Stella.NIL)), Stella.NIL)))));
  }