}    if(previousContainsEmpty)    {      result.setEmpty();    }    else    {      result.clearEmpty();    }    return result;  }  static SymbolSet[] FOLLOW;  static void computeFollow()  {    // Get terminals, nonterminals and productions    Symbol[] terminals = Symbol.terminals();    Symbol[] nonterminals = Symbol.nonterminals();    Production[] productions = Production.productions();    // Initialize FOLLOW(A) to {}    FOLLOW = new SymbolSet[nonterminals.length];    for(int i = 0; i < nonterminals.length; i++)    {      FOLLOW[i] = new SymbolSet();    }    // Place eof in FOLLOW(S) where S is the start symbol.    FOLLOW[startSymbol].setTerminal(eof);    // If there is a production A->xBy, then everything in FIRST(y) except    // for empty is placed in FOLLOW(B).    for(int i = 0; i < productions.length; i++)    {      Symbol[] rightside = productions[i].rightside();      for(int j = 0; j < rightside.length; j++)      {        if(!rightside[j].terminal)        {          SymbolSet set            = FIRST(rightside, j + 1);          set.clearEmpty();          FOLLOW[rightside[j].index].or(set                                       );        }      }    }    // If there is a production A->xB, or a production A->xBy where FIRST(y)    // contains empty, then everything in FOLLOW(A) is in FOLLOW(B).    boolean changed;    do    {      changed = false;      for(int i = 0; i < productions.length; i++)      {        Symbol[] rightside = productions[i].rightside();        for(int j = 0; j < rightside.length; j++)        {          if(!rightside[j].terminal)          {            SymbolSet before =              (SymbolSet) FOLLOW[rightside[j].index].clone();            if(FIRST(rightside, j + 1).getEmpty())            {              FOLLOW[rightside[j].index].              or(FOLLOW[productions[i].leftside]);            }            if(!before.equals(FOLLOW[rightside[j].index]))            {              changed = true;            }          }        }      }    }    while(changed);  }  static SymbolSet FOLLOW(int nonterminal)  {    return FOLLOW[nonterminal];  }  static LR0ItemSet CLOSURE(LR0Item item)  {    LR0ItemSet result = (LR0ItemSet) fastLr0Closure.get(item);    if(result != null)    {      return result;    }    result = new LR0ItemSet();    result.set(item);    LR0ItemSet newItems = result;    boolean modified;    do    {      modified = false;      LR0Item[] items = newItems.items();      newItems = new LR0ItemSet();      for(int i = 0; i < items.length; i++)      {        Production production = Production.production(items[i].production);        Symbol[] rightside = production.rightside();        if(items[i].position < rightside.length)        {          Symbol symbol = rightside[items[i].position];          if(!symbol.terminal)          {            Production[] alternatives =              Production.alternatives(symbol.index);            for(int j = 0; j < alternatives.length; j++)            {              LR0Item newItem = new LR0Item(alternatives[j].index, 0);              if(!result.get(newItem))              {                result.set(newItem);                newItems.set(newItem);                modified = true;              }            }          }        }      }    }    while(modified);    fastLr0Closure.put(item, result);    return result;  }  //    private static final SplayTreeMap fastLr0SetClosure = new SplayTreeMap();  static LR0ItemSet CLOSURE(LR0ItemSet set                             )  {    LR0ItemSet result =      /*        (LR0ItemSet) fastLr0SetClosure.get(set);                if(result != null)        {        return result;        }                result =*/      new LR0ItemSet();    LR0Item[] setItems = set.items();    for(int i = 0; i < setItems.length; i++)    {      LR0Item[] items = CLOSURE(setItems[i]).items();      for(int j = 0; j < items.length; j++)      {        result.set(items[j]);      }    }    // fastLr0SetClosure.put(set, result);    return result;  }  static LR1ItemSet CLOSURE(LR1Item item)  {    LR1ItemSet result = (LR1ItemSet) fastLr1Closure.get(item);    if(result != null)    {      return result;    }    result = new LR1ItemSet();    result.set(item);    LR1ItemSet newItems = result;    boolean modified;    do    {      modified = false;      LR1Item[] items = newItems.items();      newItems = new LR1ItemSet();      for(int i = 0; i < items.length; i++)      {        Production production = Production.production(items[i].lr0Item.production);        Symbol[] rightside = production.rightside();        if(items[i].lr0Item.position < rightside.length)        {          Symbol symbol = rightside[items[i].lr0Item.position];          if(!symbol.terminal)          {            Vector tailVector = new Vector(0);            for(int k = items[i].lr0Item.position + 1; k < rightside.length; k++)            {              tailVector.addElement(rightside[k]);            }            tailVector.addElement(Symbol.symbol(items[i].terminal, true));            Symbol[] tail = new Symbol[tailVector.size()];            tailVector.copyInto(tail);            Symbol[] symbols = FIRST(tail).getSymbols();            Production[] alternatives =              Production.alternatives(symbol.index);            for(int k = 0; k < symbols.length; k++)            {              if(symbols[k].terminal)              {                for(int j = 0; j < alternatives.length; j++)                {                  LR1Item newItem = new LR1Item(                                      new LR0Item(alternatives[j].index, 0),                                      symbols[k].index);                  if(!result.get(newItem))                  {                    result.set(newItem);                    newItems.set(newItem);                    modified = true;                  }                }              }            }          }        }      }    }    while(modified);    fastLr1Closure.put(item, result);    return result;  }  // private static final SplayTreeMap fastLr1SetClosure = new SplayTreeMap();  static LR1ItemSet CLOSURE(LR1ItemSet set                             )  {    LR1ItemSet result =      /*        (LR1ItemSet) fastLr1SetClosure.get(set);                if(result != null)        {        return result;        }                result =*/      new LR1ItemSet();    LR1Item[] setItems = set.items();    for(int i = 0; i < setItems.length; i++)    {      LR1Item[] items = CLOSURE(new LR1Item(setItems[i].lr0Item, dummy)).items();      for(int j = 0; j < items.length; j++)      {        result.set(new LR1Item(items[j].lr0Item,                               items[j].terminal == dummy ? setItems[i].terminal : items[j].terminal));      }    }    //        fastLr1SetClosure.put(set, result);    return result;  }  static LR0ItemSet GOTO(LR0ItemSet set                           , Symbol symbol)  {    LR0ItemSet initialset = set                              ;    set      = CLOSURE(set               );    LR0ItemSet result = new LR0ItemSet();    // return all items A->xS.y such that A->x.Sy is in set. (S=symbol)    LR0Item[] items = set.items();    for(int i = 0; i < items.length; i++)    {      Production production = Production.production(items[i].production);      Symbol[] rightside = production.rightside();      if(items[i].position < rightside.length)      {        if(symbol.equals(rightside[items[i].position]))        {          result.set(new LR0Item(items[i].production,                                 items[i].position + 1));        }      }    }    return result;  }}