/// <summary>
/// LR(0)的Closure操作。
/// 补全一个状态。
/// </summary>
/// <param name="list"></param>
/// <param name="state"></param>
/// <returns></returns>
static LR0State Closure(this RegulationList list, LR0State state)
{
Queue <LR0Item> queue = new Queue <LR0Item>();
foreach (var item in state)
{
queue.Enqueue(item);
}
while (queue.Count > 0)
{
LR0Item item = queue.Dequeue();
TreeNodeType node = item.GetNodeNext2Dot();
if (node == null)
{
continue;
}
foreach (var regulation in list)
{
if (regulation.Left == node)
{
var newItem = new LR0Item(regulation, 0);
if (state.TryInsert(newItem))
{
queue.Enqueue(newItem);
}
}
}
}
return(state);
}
/// <summary>
/// LR(0)的Goto操作。
/// 将圆点移到所有LR(0)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>
/// <returns></returns>
static LR0State Goto(this RegulationList list, LR0State state, TreeNodeType x)
{
LR0State toState = new LR0State();
foreach (var item in state)
{
TreeNodeType nextNode = item.GetNodeNext2Dot();
if (nextNode == x)
{
var newItem = new LR0Item(item.Regulation, item.DotPosition + 1);
toState.TryInsert(newItem);
}
}
return(Closure(list, toState));
}
