sclass AI_BottomUpParser1 {

  Map<S, Set<S>> wordsToCategories;

  bool splitSplittables = true; // e.g. what's => what is

  S productionsText;

  L<Word> words;

  L<S> rawWords;

  L<S> cnc; // words + N tokens (null if unknown)

  new LinkedHashSet<Updatable> allObjects;

  long changes, iterations;

  new MultiMap<S, WeightedProduction> productionsByA;

  new MultiMap<S> subClasses;

  bool mergeGroupsInSamePosition = true;

  new HashMap<IntRange, Word> groupsByPosition;

  bool verbose_callPlausibilityFunction;

  Map<Int, L<S>> categoriesAtWordIndex; // user can set categories for each token

  int maxDepth = 100;

  bool maxDepthReached;

  // callbacks

  Runnable afterIteration, afterParse;

  class Updatable {

    void update {}

    void setField(S field, O value) {

      if (eq(get(this, field), value)) ret;

      set(this, field, value);

      change();

    }

  }

  class Expectation {

    S ifClass;

    Runnable action;

    *() {}

    *(S *ifClass, Runnable *action) {}

  }

  class Word extends Updatable {

    S text; // or null if unknown

    int wordFrom, wordTo; // token indices

    new LinkedHashSet<Word> prev;

    new LinkedHashSet<Word> next;

    new LinkedHashSet<L<Word>> constituents; // if group

    new L<Expectation> expectations;

    new L<Expectation> fulfilledExpectations;

    new TreeSet<S> classes;

    int classesConvertedToTraits;

    new LinkedHashSet<Word> groups; // I am part of

    new L<Trait> traits;

    *() {}

    *(S *text, int *wordFrom, int *wordTo) {

      classes.add(quote(lower(text)));

    }

    void update {

      // Add direct word classes

      if (text != null)

        for (S c : unnull(wordsToCategories.get(text)))

          addClass(c);

      // Process expectations

      for (Expectation e : cloneList(expectations)) {

        //print("Checking expected class " + e.ifClass);

        if (classes.contains(e.ifClass)) {

          moveElementFromCollectionToCollection(e, expectations, fulfilledExpectations);

          change();

          callF(e.action);

        }

      }

      if (l(classes) > classesConvertedToTraits) {

        for (fS c : dropFirst(classesConvertedToTraits, classes))

          addTraitsForClass(c);

        classesConvertedToTraits = l(classes);

      }

      for (Trait t : iterateListConcurrently(traits))

        t.update();

    }

    bool isGroup() { ret nempty(constituents); }

    bool addClass(S c) {

      if (!classes.addAll(makeHull_optimized(subClasses, c))) false;

      change(); true;

    }

    void addExpectation(Expectation e) {

      //print("addExpectation " + e);

      expectations.add(e);

      change();

    }

    void addTraitsForClass(S c) {

      for (WeightedProduction p : productionsByA.get(c))

        addTrait(new LinkWithTo(p.b, p.c, p.plausibilityFunction));

    }

    void addTrait(Trait t) {

      set(t, w := this);

      traits.add(t);

    }

    toString {

      ret textAndClasses(this);

    }

    bool hasClass(S c) { ret contains(classes, c); }

    S text() { ret text; }

  } // end of class Word

  Word makeGroup(Word a, Word b, S newClass) {

    L<Word> list = null;

    Word g = null;

    if (mergeGroupsInSamePosition)

      g = groupsByPosition.get(IntRange(a.wordFrom, b.wordTo));

    else { 

      list = ll(a, b);

      // look for existing group

      for (Word _g : a.groups)

        if (contains(_g.constituents, list)) { g = _g; break; }

    }

    if (list == null) list = ll(a, b);

    if (g != null) {

      g.constituents.add(list);

      if (g.addClass(newClass)) {

        //print("Added class " + newClass + " to existing group: " + a.text + " + " + b.text);

      }

      ret g;

    }

    // new group

    //print("Making group " + newClass + " " + a.text + " + " + b.text);

    //print("  prev=" + sfu(collect(a.prev, 'text)));

    //print("  next=" + sfu(collect(b.next, 'text)));

    g = new Word(joinWithSpace(a.text, b.text), a.wordFrom, b.wordTo);

    allObjects.add(g);

    if (mergeGroupsInSamePosition)

      groupsByPosition.put(IntRange(a.wordFrom, b.wordTo), g);

    g.addClass(newClass);

    g.constituents.add(list);

    for (Word w : list)

      w.groups.add(g);

    g.prev.addAll(a.prev);

    g.next.addAll(b.next);

    for (Word prev : a.prev) prev.next.add(g);

    for (Word next : b.next) next.prev.add(g);

    ret g;

  }

  class Trait extends Updatable {

    Word w;

  }

  class LinkWithTo extends Trait {

    S linkWith, linkTo; // classes

    S plausibilityFunction;

    int expectationsSentToNext;

    *() {}

    *(S *linkWith, S *linkTo, S *plausibilityFunction) {}

    void update {

      if (l(w.next) > expectationsSentToNext) {

        for (final Word next : dropFirst(expectationsSentToNext, w.next))

          next.addExpectation(new Expectation(linkWith, r {

            if (ai_parser_activateStandardFunctions_get() && plausibilityFunction != null) {

              loadFunctions_preferDiskCache(); // note: changes this for whole program

              O result = pcallAndMake(plausibilityFunction, w.text, next.text);

              if (verbose_callPlausibilityFunction)

                print("Called plausibility function " + plausibilityFunction + ": " + w.text + " + " + next.text + " => " + result);

              if (isFalse(result))

                ret;

            }

            makeGroup(w, next, linkTo)

          }));

        expectationsSentToNext = l(w.next);

      }

    }

  }

  void parse(L<S> tok) {

    cnc = /*simpleSpaces2*/(tok);

    rawWords = codeTokens(cnc);

    _parse();

  }

  AI_BottomUpParser1 parse(fS sentence) {

    rawWords = words_withAngleBrackets(sentence);

    _parse();

    this;

  }

  void _parse() {

    if (words != null) fail("only call once");

    if (splitSplittables)

      ai_splitSplittables(rawWords);

    if (wordsToCategories == null) wordsToCategories = ai_wordToCategories();

    parseProductions();

    words = new L;

    for i over rawWords: {

      Word w = new(rawWords.get(i), i, i+1);

      words.add(w);

      if (isAngleBracketed(w.text)) w.addClass(w.text);

      else if (isQuoted(w.text)) w.addClass("<noun>");

      else if (isInteger(w.text)) w.addClass("<number>");

      for (S cat : unnull(mapGet(categoriesAtWordIndex, i))) w.addClass(cat);

    }

    for (int i = 0; i < l(words)-1; i++)

      linkWords(words.get(i), words.get(i+1));

    //printStruct(first(words));

    addAll(allObjects, words);

    long lastChanges;

    do {

      lastChanges = changes;

      //print(n2(changes, "change"));

      for (Updatable w : cloneList(allObjects))

        w.update();

      ++iterations;

      callF(afterIteration);

    } while (licensed() && lastChanges != changes);

    callF(afterParse);

  }

  void printWordsAndGroups() {

    for (Word w : words) print("  " + textAndClasses(w));

    print();

    L<Word> groups = groups();

    print();

    print(n2(groups, "group"));

    for (Word g : groups)

      print("Group: " + groupedTextAndClasses(g));

  }

  void printConstituentsOfFullGroup() {

    Word g = fullGroup();

    if (g == null) ret;

    print();

    pnl(allGroupings(g));

  }

  L<Word> words() { ret instancesOf(Word.class, allObjects); }

  L<Word> groups() { ret [Word w : words() | w.isGroup()]; }

  // only one with default flags

  L<Word> fullGroups() {

    ret filterByFields(words(), wordFrom := 0, wordTo := l(words));

  }

  Word fullGroup() {

    ret findByFields(words(), wordFrom := 0, wordTo := l(words));

  }

  Set<S> fullClasses() {

    new TreeSet<S> set;

    for (Word g : fullGroups())

      set.addAll(g.classes);

    ret set;

  }

  S bracketStuff(Word w) {

    ret " (" + joinWithComma(w.classes) +

      + (empty(w.constituents) ? "" : ", " + n2(w.constituents, "grouping")) +  ")";

  }

  S textAndClasses(Word w) { ret w.text + bracketStuff(w); }

  S groupedTextAndClasses(Word w) { ret grouped(w) + bracketStuff(w); }

  S fullGrouped() { ret grouped(fullGroup()); }

  void linkWords(Word a, Word b) {

    a.next.add(b);

    b.prev.add(a);

  }

  void change() { ++changes; }

  void parseProductions() {

    for (WeightedProduction p : 

      productionsText == null ? ai_buParser_parseWeightedProductions() : ai_buParser_parseWeightedProductions(productionsText))

      if (p.b != null)

        productionsByA.put(p.a, p);

      else

        subClasses.put(p.a, p.c);

  }

  // TODO: now there are multiple groupings

  S grouped(Word g) {

    if (g == null) null;

    if (empty(g.constituents)) ret g.text;

    ret groupedConstituents(first(g.constituents));

  }

  S groupedConstituents(L<Word> constituents) {

    new L<S> l;

    for (Word w : constituents)

      l.add(curlyBraceIfMultipleTokens(grouped(w)));

    ret joinWithSpace(l);

  }

  Set<S> allGroupings(Word g) {

    if (empty(g.constituents)) ret litorderedset(g.text);

    new LinkedHashSet<S> set;

    for (L<Word> l : g.constituents)

      set.add(groupedConstituents(l));

    ret set;

  }

}