abstract sclass TripleRef<A> {
  Triple<A> triple;

  *() {}
  *(Triple<A> *triple) {}
  
  A get() {
    ret tripleAtPosition(triple(), position());
  }
  
  Triple<A> triple() { ret triple; }
  
  // 0 = a, 1 = b, 2 = c
  abstract int position();
  
  // currently compares triple with ==
  public bool equals(O o) {
    if (!o instanceof TripleRef) false;
    ret position() == o/TripleRef.position() && triple == o/TripleRef.triple;
  }
}