/// <summary>
/// LR(1)的Closure操作。
/// 补全一个状态。
/// </summary>
/// <param name="grammar"></param>
/// <param name="state"></param>
/// <returns></returns>
static SmallerLR1State Closure(this RegulationList grammar, SmallerLR1State state,
Dictionary <TreeNodeType, bool> nullableDict = null, FIRSTCollection firstCollection = null)
{
if (nullableDict == null)
{
grammar.GetNullableDict(out nullableDict);
}
if (firstCollection == null)
{
grammar.GetFirstCollection(out firstCollection, nullableDict);
}
Queue <LR1Item> queue = new Queue <LR1Item>();
foreach (var item in state)
{
queue.Enqueue(item);
}
while (queue.Count > 0)
{
LR1Item item = queue.Dequeue();
TreeNodeType node = item.GetNodeNext2Dot();
if (node == null || node.IsLeave)
{
continue;
}
List <TreeNodeType> betaZ = item.GetBetaZ();
FIRST first = grammar.GetFirst(firstCollection, nullableDict, betaZ);
List <Regulation> regulations = grammar.GetRegulations(node);
foreach (var regulation in regulations)
{
foreach (var value in first.Values)
{
LR1Item newItem = new LR1Item(regulation, 0, value);
if (state.TryInsert(newItem))
{
queue.Enqueue(newItem);
}
}
}
}
return(state);
}
