abstract sclass PartialAttractor implements Runnable {
  VF1<PartialAttractor> action;
  
  LS tok;
  IntRange matchedRange;

  public abstract bool find(); // uses tok
  public void run { callF(action, this); }
  
  toString { ret standard_toString(this); }
  
  bool acceptFull() {
    matchedRange = intRange(0, l(tok));
    true;
  }
  
  S matchedString() {
    ret joinSubList(tok, matchedRange);
  }
  
  LS tok() {
    ret subList(tok, matchedRange);
  }
}