private void AddZeroRule()
{
string newHead = beginToken + "'";
TransRule zeroRule = new TransRule(new TransToken(newHead),
new List <TransToken> {
new TransToken(beginToken)
},
(TransRule thisPlaceholder) =>
{ thisPlaceholder.head.attrVal = thisPlaceholder.body[0].attrVal; });
rules.Insert(0, zeroRule);
beginToken = newHead;
}
private HashSet <TransToken> GetNextTokenFirsts(TransRule rule, int nextTokenIndex)
{
HashSet <TransToken> result = new HashSet <TransToken> {
};
bool containsEpsilon = true;
for (int i = nextTokenIndex; i < rule.body.Count; ++i)
{
TransToken token = rule.body[i];
containsEpsilon = false;
if (terms.Contains(token))
{
result.Add(token);
break;
}
foreach (TransToken first in firstSets[token])
{
if (first.Equals(new TransToken("")))
{
containsEpsilon = true;
}
result.Add(first);
}
containsEpsilon |= firstSets[token].Count == 0;
if (!containsEpsilon)
{
break;
}
}
if (containsEpsilon)
{
result.Add(new TransToken(""));
}
return(result);
}
private Action CreateReduceCallback(int ruleIndex)
{
return(() => {
TransRule rule = parent.rules[ruleIndex];
for (int i = rule.body.Count; i > 0; --i)
{
stateStack.Pop();
}
for (int i = rule.body.Count - 1; i >= 0; --i)
{
rule.body[i] = tokenStack.Pop();
}
rule.ApplyRule();
tokenStack.Push(rule.head);
stateStack.Push(GetStateFromGoto(stateStack.Peek(), tokenStack.Peek()));
});
}
private TItemState Goto(TItemState itemState, TransToken nextTerm)
{
HashSet <TItem> resultingSet = new HashSet <TItem> {
};
foreach (TItem item in itemState.stateItems)
{
TransRule rule = parent.rules[item.ruleNum];
if (rule.body.Count == item.dotPos)
{
continue;
}
if (rule.body[item.dotPos].token == nextTerm.token)
{
resultingSet.Add(new TItem(item.ruleNum, item.dotPos + 1));
}
}
return(new TItemState(resultingSet));
}
// If rule contains body other than one empty symbol, create firsts set for it
private bool ComputeBodyFirstSets(Dictionary <TransToken, HashSet <TransToken> > firstSets, TransRule rule)
{
bool notDone = false;
bool containsEpsilon = true;
foreach (TransToken token in rule.body)
{
containsEpsilon = false;
if (terms.Contains(token))
{
notDone |= firstSets[rule.head].Add(token);
break;
}
foreach (TransToken element in firstSets[token])
{
if (element.Equals(new TransToken("")))
{
containsEpsilon = true;
}
notDone |= firstSets[rule.head].Add(element);
}
if (!containsEpsilon)
{
break;
}
}
if (containsEpsilon)
{
notDone |= firstSets[rule.head].Add(new TransToken(""));
}
return(notDone);
}
