public LRItem FindByCore(LR0Item core)
{
foreach (LRItem item in this)
{
if (item.Core == core)
{
return(item);
}
}
return(null);
}
private static int CompareLR0Items(LR0Item x, LR0Item y)
{
if (x.ID < y.ID)
{
return(-1);
}
if (x.ID == y.ID)
{
return(0);
}
return(1);
}
private Production CreateProduction(NonTerminal lvalue, BnfTermList operands)
{
Production prod = new Production(lvalue);
GrammarHintList hints = null;
//create RValues list skipping Empty terminal and collecting grammar hints
foreach (BnfTerm operand in operands)
{
if (operand == Grammar.CurrentGrammar.Empty)
{
continue;
}
//Collect hints as we go - they will be added to the next non-hint element
GrammarHint hint = operand as GrammarHint;
if (hint != null)
{
if (hints == null)
{
hints = new GrammarHintList();
}
hints.Add(hint);
continue;
}
//Check if it is a Terminal or Error element
Terminal t = operand as Terminal;
if (t != null)
{
prod.Flags |= ProductionFlags.HasTerminals;
if (t.Category == TokenCategory.Error)
{
prod.Flags |= ProductionFlags.IsError;
}
}
//Add the operand info and LR0 Item
LR0Item item = new LR0Item(_lastItemId++, prod, prod.RValues.Count, hints);
prod.LR0Items.Add(item);
prod.RValues.Add(operand);
hints = null;
}//foreach operand
//set the flags
if (prod.RValues.Count == 0)
{
prod.Flags |= ProductionFlags.IsEmpty;
}
//Add final LRItem
prod.LR0Items.Add(new LR0Item(_lastItemId++, prod, prod.RValues.Count, hints));
return(prod);
}
}//method
public LRItem AddItem(LR0Item core)
{
var item = AllItems.FindByCore(core);
if (item != null)
{
return(item);
}
item = new LRItem(State, core);
AddItem(item);
//If current term is non-terminal, expand it
var currNt = core.Current as NonTerminal;
if (currNt == null)
{
return(item);
}
foreach (var prod in currNt.Productions)
{
var expItem = AddItem(prod.LR0Items[0]);
item.Expansions.Add(expItem);
}
return(item);
}//method
public readonly BnfTermSet Lookaheads = new BnfTermSet(); //actual active lookaheads
public LRItem(ParserState state, LR0Item core)
{
State = state;
Core = core;
Key = state.Name + "/" + core.ID;
}
