sclass WaitForName {
  persistently swappable S answer(S s) {
    S name = nameFromInput(s);
    if (name != null) {
      cancel();
      ret processName(s);
    }
    ret otherInput(s);
  }
  
  persistently swappable S nameFromInput(S s) { ret s; }
  persistently swappable S otherInput(S s) { ret "I don't understand. Yes or no?"; }
  persistently swappable S processName(S name) { ret "You said: " + name; }
  persistently swappable void cancel() { print("Cancelling"); }
}