sclass ActualThoughtSpace extends AbstractThoughtSpace {
  new TripleIndex index;
  int limit; // 0 = no limit
  Map<TripleWeb, Bool> blocked = newWeakHashMap();

  *() {}
  *(int *limit) {}
  
  // existence of triple has already been checked
  public S postTriple(T3<S> t) {
    if (limitReached()) fail("Thought space limit reached");
    TripleWeb w = tripleWeb(t);
    index.addTriple(w);
    ret w.globalID();
  }
  
  bool limitReached() {
    ret limit > 0 && size() >= limit;
  }
  
  L<WebNode> get(S s) {
    L<WebNode> l = filterNonBlocked(parent.get(s));
    ret combineLists(l, index.get(ai_shortenForIndex(s)));
  }
  
  L<WebNode> filterNonBlocked(L<WebNode> l) {
    ...
  }
  
  int size() { ret l(websByID); }
}