abstract sclass WordTokRule extends Attractor implements RuleOnTok, RuleOnString, RuleOnExtTok, RuleOnExtS {

  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;

  }

  public final bool matches(ExtS s) {

    process(s);

    ret matched();

  }

  public final bool matches(S s) {

    process(s);

    ret matched();

  }

  public void process(S s) {

    process(ext(s));

  }

  public void process(ExtS s) {

    processExtTok(extLift(wordTok(s!), s));

  }

  public void processTok(LS tok) {

    processExtTok(ext(tok));

  }

  public void processExtTok(Ext<LS> tok) {

    if (!preCheck(tok)) ret;

    map = nullIfContainsKeysOtherThan(gazelle_zipTwoTokenizationsToMap(tokPat(), tok!), vars);

    if (debug) print(pattern + " + " + join(tok!) + " => " + map);

  }

  bool preCheck(DynamicObject o) { true; }

  bool matched() { ret map != null; }

  S getVar(S name) { ret getOrKeep(map, name); }

}