sclass InputProcessor1 {
  Map<S, virtual F1<S, O>> propertyMakers = ciMap();
  
  sclass Out > PropertiesAndErrors {
    InputProcessor1 inputProcessor;
    S input;
    
    bool hasProperty(S name) {
      ret properties.containsKey(name) || containsKey(propertyErrors, name);
    }
    
    void triggerProperty(S name) {
      if (inputProcessor == null || hasProperty(name)) ret;
      O f = inputProcessor.propertyMakers.get(name);
      if (f == null) ret;
      propertiesAndErrors_callF(this, name, f, input);
    }
    
    O getProperty(S name) {
      if (properties.containsKey(name)) ret properties.get(name);
      if (containsKey(propertyErrors, name)) throw throwPersistableThrowable(mapGet(propertyErrors, name));
      triggerProperty(name);
      if (containsKey(propertyErrors, name)) throw throwPersistableThrowable(mapGet(propertyErrors, name));
      ret properties.get(name);
    }
    
    Out detach() { inputProcessor = null; this; }
  }

  Out process(S input) {
    Out out = dontProcess(input);
    for (S name : keys(propertyMakers))
      out.triggerProperty(name);
    ret out;
  }
  
  // you can query properties on demand
  Out dontProcess(S input) {
    ret nu Out(inputProcessor := this, +input);
  }
  
  void addStandardFunctions(S... names) {
    putAllAsKeyAndValue(propertyMakers, names);
  }
}