/// <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>
/// 从一个LR(0)状态跳转到另一个LR(0)状态
/// </summary>
/// <param name="from"></param>
/// <param name="x"></param>
/// <param name="to"></param>
public LR0Edge(LR0State from, TreeNodeType x, LR0State to)
: base(GetUniqueString)
{
this.From = from;
this.X = x;
this.To = to;
}
/// <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));
}
/// <summary>
/// 用SLR分析法计算分析表
/// </summary>
/// <param name="grammar"></param>
/// <returns></returns>
public static void GetSLRParsingMap(this RegulationList grammar,
out LRParsingMap map,
out LR0StateCollection stateCollection,
out LR0EdgeCollection edgeCollection, TextWriter writer)
{
// 给文法添加一个辅助的开始产生式 S' -> S $
// 如何添加一个外来的结点类型？用Enum是无法做到的。
var decoratedS = new TreeNodeType("__S2", "S'", "<S'>");
var decoratedEnd = TreeNodeType.endOfTokenListNode;
var decoratedRegulation = new Regulation(
decoratedS, grammar[0].Left, decoratedEnd);
var decoratedGrammar = new RegulationList(decoratedRegulation);
decoratedGrammar.AddRange(grammar);
// 初始化T为{ Closure(S' -> S $) }
var firstItem = new LR0Item(decoratedGrammar[0], 0);
var firstState = new LR0State(firstItem);
firstState = decoratedGrammar.Closure(firstState);
stateCollection = new LR0StateCollection(firstState);
edgeCollection = new LR0EdgeCollection(stateCollection);
var queue = new Queue <LR0State>();
queue.Enqueue(firstState);
int lastOutputLength = 0;
int stateListCount = 1;
int queueCount = 1;
while (queue.Count > 0)
{
LR0State fromState = queue.Dequeue(); queueCount--;
int itemIndex = 0;
int itemCount = fromState.Count();
foreach (var item in fromState)
{
{
TextWriter currentWriter = Console.Out;
if (Console.Out != writer)
{
Console.SetOut(writer);
}
for (int i = 0; i < lastOutputLength; i++)
{
Console.Write('\u0008');
}
string output = string.Format("Calculating SLR State List: {0} <-- {1}, working on {2}/{3} ...",
stateListCount, queueCount, 1 + itemIndex++, itemCount);
Console.Write(output);
lastOutputLength = output.Length;
Console.SetOut(currentWriter);
}
TreeNodeType x = item.GetNodeNext2Dot();
if (x == null || x == decoratedEnd)
{
continue;
}
LR0State toState = decoratedGrammar.Goto(fromState, x);
if (stateCollection.TryInsert(toState))
{
queue.Enqueue(toState);
stateListCount++;
queueCount++;
var edge = new LR0Edge(fromState, x, toState);
edgeCollection.TryInsert(edge);
}
else
{
int index = stateCollection.IndexOf(toState);
toState = stateCollection[index];
var edge = new LR0Edge(fromState, x, toState);
edgeCollection.TryInsert(edge);
}
}
}
{
TextWriter currentWriter = Console.Out;
if (Console.Out != writer)
{
Console.SetOut(writer);
}
Console.WriteLine();
Console.SetOut(currentWriter);
}
map = new LRParsingMap();
foreach (var edge in edgeCollection)
{
if (edge.X.IsLeave)
{
int stateId = edge.From.ParsingMapIndex + 1; //stateCollection.IndexOf(edge.From) + 1
int gotoStateId = edge.To.ParsingMapIndex + 1; //stateCollection.IndexOf(edge.To) + 1
map.SetAction(stateId, edge.X, new LR1ShiftInAction(gotoStateId));
}
else
{
int stateId = edge.From.ParsingMapIndex + 1; //stateCollection.IndexOf(edge.From) + 1
int gotoStateId = edge.To.ParsingMapIndex + 1; //stateCollection.IndexOf(edge.To) + 1
map.SetAction(stateId, edge.X, new LR1GotoAction(gotoStateId));
}
}
var endItem = new LR0Item(decoratedRegulation, 1);
FOLLOWCollection followCollection;
decoratedGrammar.GetFollowCollection(out followCollection);
foreach (var state in stateCollection)
{
if (state.Contains(endItem))
{
int stateId = state.ParsingMapIndex + 1;//stateCollection.IndexOf(state) + 1
map.SetAction(stateId, decoratedEnd, new LR1AceptAction());
}
foreach (var lr0Item in state)
{
if (lr0Item.GetNodeNext2Dot() == null)
{
FOLLOW follow = FindFollow(followCollection, lr0Item.Regulation.Left);
foreach (var value in follow.Values)
{
int stateId = state.ParsingMapIndex + 1;// stateCollection.IndexOf(state) + 1;
int reductionId = decoratedGrammar.IndexOf(lr0Item.Regulation);
var action = new LR1ReducitonAction(reductionId);
map.SetAction(stateId, value, action);
}
}
}
}
}
