static SS ai_negateVerb_map = litcimap_bidi("isn't", "is", "are", "aren't", "am", "am not");

static S ai_negateVerb(S verb) {
  try answer mapGet(ai_negateVerb_map, verb);
  if (isThirdPersonVerb(verb)) ret "doesn't " + verbToBaseForm(verb);
  ret "don't " + verb;
}