public void AddItem(LR0Item core)
{
//Check if a core had been already added. If yes, simply return
if (!_allCores.Add(core))
{
return;
}
//Create new item, add it to AllItems, InitialItems, ReduceItems or ShiftItems
var item = new LRItem(_state, core);
AllItems.Add(item);
if (item.Core.IsFinal)
{
ReduceItems.Add(item);
}
else
{
ShiftItems.Add(item);
}
if (item.Core.IsInitial)
{
InitialItems.Add(item);
}
if (core.IsFinal)
{
return;
}
//Add current term to ShiftTerms
if (!ShiftTerms.Add(core.Current))
{
return;
}
if (core.Current is Terminal)
{
ShiftTerminals.Add(core.Current as Terminal);
}
//If current term (core.Current) is a new non-terminal, expand it
var currNt = core.Current as NonTerminal;
if (currNt == null)
{
return;
}
foreach (var prod in currNt.Productions)
{
AddItem(prod.LR0Items[0]);
}
}
private Production CreateProduction(NonTerminal lvalue, BnfTermList operands)
{
var prod = new Production(lvalue);
GrammarHintList hints = null;
//create RValues list skipping Empty terminal and collecting grammar hints
foreach (var operand in operands)
{
if (operand == _grammar.Empty)
{
continue;
}
//Collect hints as we go - they will be added to the next non-hint element
if (operand is GrammarHint hint)
{
if (hints == null)
{
hints = new GrammarHintList();
}
hints.Add(hint);
continue;
}
//Add the operand and create LR0 Item
prod.RValues.Add(operand);
var lr0 = new LR0Item(_lastItemId++, prod, prod.RValues.Count - 1, hints);
prod.LR0Items.Add(lr0);
hints = null;
}
//set the flags
if (prod.RValues.Count == 0)
{
prod.Flags |= ProductionFlags.IsEmpty;
}
//Add final LRItem
ComputeProductionFlags(prod);
prod.LR0Items.Add(new LR0Item(_lastItemId++, prod, prod.RValues.Count, hints));
return(prod);
}
public LRItem FindByCore(LR0Item core)
{
return(this.FirstOrDefault(item => item.Core == core));
}