/// <summary>
/// LR(1)的Goto操作。
/// 将圆点移到所有LR(1)项中的符号<paramref name="x"/>之后。
/// </summary>
/// <param name="list"></param>
/// <param name="state"></param>
/// <param name="x">一个文法符号，终结点或非终结点。</param>
/// <param name="firstList"></param>
/// <returns></returns>
static LALR1State Goto(this RegulationList list, LALR1State state, TreeNodeType x, Dictionary <TreeNodeType, bool> nullableDict, FIRSTCollection firstList = null)
{
var toState = new LALR1State();
foreach (var group in state.GetGroups())
{
TreeNodeType nextNode = group.Item1.GetNodeNext2Dot();
if (nextNode == x)
{
toState.TryInsert(
new LR0Item(group.Item1.Regulation, group.Item1.DotPosition + 1),
group.Item2);
}
}
return(Closure(list, toState, nullableDict, firstList));
}
/// <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 LALR1State Closure(this RegulationList grammar, LALR1State 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);
}
