LRNode Closure(LRNode node)
{
bool isChanged = true;
while (isChanged)
{
isChanged = false;
int prevCount = node.Elements.Count;
HashSet <LRNodeElement> toAdd = new HashSet <LRNodeElement>();
foreach (var element in node.Elements)
{
var rule = element.GrammarRule;
if (rule.DotPos >= rule.ProductionElements.Count)
{
continue;
}
var pe = rule.ProductionElements[rule.DotPos];
var next = rule.DotPos + 1 < rule.ProductionElements.Count ? rule.ProductionElements[rule.DotPos + 1] : new EpsilonProduction();
if (pe is NonTerminalProduction)
{
foreach (var r in grammarBuilder.NonTerminals[pe.Name].GetAllRules())
{
foreach (var terminal in CalculateFirst(next, element.TerminalProduction))
{
toAdd.Add(new LRNodeElement(r.Clone(), terminal));
}
}
}
}
foreach (var e in toAdd)
{
node.Elements.Add(e);
}
if (node.Elements.Count != prevCount)
{
isChanged = true;
}
}
return(node);
}
/// <summary>
/// GOTO function from dragonbook
/// </summary>
/// <param name="I"></param>
/// <param name="X"></param>
/// <returns></returns>
LRNode Goto(LRNode I, IProductionElement X)
{
LRNode node = new LRNode();
foreach (var e in I.Elements)
{
var rule = e.GrammarRule;
var terminal = e.TerminalProduction;
if (rule.DotPos < rule.ProductionElements.Count)
{
var pe = rule.ProductionElements[rule.DotPos];
//TODO : think about removing first part of condition.
if (pe.GetType().Equals(X.GetType()) && X.Name.Equals(pe.Name))
{
var newRule = rule.Clone();
newRule.DotPos++;
node.Elements.Add(new LRNodeElement(newRule, terminal));
}
}
}
return(Closure(node));
}
