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();
  
  toString {
    ret position() + "@" + triple;
  }
}