// You can either override process(S) or process(ExtS)
// depending on whether you need any extra info
abstract sclass WordTokRule extends Attractor implements RuleOnTok, RuleOnString {
  S pattern; // example sentence
  Set<S> vars; // list of the variable words in the sentence
  bool debug;

  transient LS tokPat; // parsed pattern
  transient SS map; // not null if there is a match
  
  *() {}
  *(S *pattern, S... vars) { this.vars = litciset(vars); }
  *(S *pattern, Set<S> *vars) {}
  
  LS tokPat() {
    if (tokPat == null) tokPat = wordTok(pattern);
    ret tokPat;
  }
  
  // override me
  bool validate() { true; }
  
  public bool matches(ExtS s) { ret matches(s); }
  
  public bool matches(S s) {
    process(s);
    if (map != null && !validate())
      map = null;
    ret matched();
  }
  
  public void process(ExtS s) { process(s!); }
  public void process(S s) { process(wordTok(s)); }
  public void process(LS tok) {
    map = nullIfContainsKeysOtherThan(gazelle_zipTwoTokenizationsToMap(tokPat(), tok), vars);
    if (debug) print(pattern + " + " + join(tok) + " => " + map);
  }
  
  bool matched() { ret map != null; }
  S getVar(S name) { ret getOrKeep(map, name); }
  
  void reset { map = null; }
}