!7

// not tested on null values
sclass FieldIndex implements IConceptIndex {
  //Concepts concepts;
  Class<? extends Concept> c;
  S field;
  new HashMap<Concept, O> objectToValue;
  new MultiMap<O, Concept> valueToObject;
  
  *() {}
  *(Concepts concepts, Class<? extends Concept> *c, S *field) {
    for (Concept c : list(concepts, c))
      update(c);
  }
  
  public void update(Concept c) {
    O newValue = cget(c, field);
    O oldValue = objectToValue.get(c);
    if (newValue != oldValue) {
      valueToObject.remove(oldValue, c);
      valueToObject.add(newValue, c);
      objectToValue.put(c, value);
    }
  }
  
  public void remove(Concept c) {
    O value = cget(c, field);
    objectToValue.remove(c);
    valueToObject.remove(value, c);
  }
}

p {
}