abstract sclass StringMatcher {
  // change matches only if returning true
  abstract bool match(S pat, S input, SS matches);
  
  // seems to be the same in all subclasses
  S apply(S input, SS matches) {
    ret replaceVars(input, matches);
  }
  
  bool matchAnyPattern(Collection<S> patterns, S input, SS matches) {
    for (S pat : unnull(patterns))
      if (match(pat, input, matches)) true;
    false;
  }
}