static Set<S> applyWordTokRules(L<WordTokRule> rules, S s) {
  ret concatListsToCISet(map(rules, rule ->
    rule.matches(s) ? getStringEmits(rule) : null
  );
}

static Set<S> applyWordTokRules(L<WordTokRule> rules, Collection<S> inputs) {
  Set<S> out = cloneLinkedCISet(inputs);
  for unnull (S input : inputs)
    functionReturningList_transitiveHull_ciSet(func(S s) -> Collection<S> { applyWordTokRules(rules, s) }, input, seen := out);
  ret out;
}