static int callAnswerMethod_version;

static S callAnswerMethod(S s) {
  if (callAnswerMethod_version == 0)
    if (hasMethod(mc(), "answer", "", new L)) callAnswerMethod_version = 1;
    else if (hasMethod(mc(), "answer", "")) callAnswerMethod_version = 2;
    else callAnswerMethod_version = -1;
  
  if (callAnswerMethod_version == 1)
    ret (S) callMC("answer", s, emptyList());
  else if (callAnswerMethod_version == 2)
    ret (S) callMC("answer", s);
  null;
}

static S callAnswerMethod(O responder, S s) {
  ret callAnswerMethod(responder, s, litlist(s));
}

static S callAnswerMethod(O responder, S s, L<S> history) {
  S answer = (S) callOpt(responder, "answer", s, history);
  if (answer == null)
    answer = (S) callOpt(responder, "answer", s);
  return emptyToNull(answer);
}