private void NTPListClone()
{
var ntplist = ProductionInfo.Production_ParserResult.ntplist;
NewNTPList = new List <NonTerminalProductionInfo>();
foreach (var pitem in ntplist)
{
var newinfo = new NonTerminalProductionInfo {
Name = pitem.Name, Item = new List <NonTerminalProductionItemInfo>()
};
foreach (var item in pitem.Item)
{
newinfo.Item.Add(new NonTerminalProductionItemInfo {
Content = item.Content.ToList()
});
}
NewNTPList.Add(newinfo);
}
}
/// <summary>
/// 消除公因子
/// </summary>
private void EliminateCommonFactor()
{
var n = NewNTPList.Count;
var newntpid = 0;
var newntpnameprefix = Production_Parser.SysNamePrefix + "U_";
for (var i = 0; i < n; i++)
{
var lastdiff = 0;
var hasdiff = false;
var minn = NewNTPList[i].Item[0].Content.Count;
for (var j = 1; j < NewNTPList[i].Item.Count; j++)
{
minn = Math.Min(minn, NewNTPList[i].Item[j].Content.Count);
}
while (!hasdiff && lastdiff < minn)
{
var curitem = NewNTPList[i].Item[0].Content[lastdiff];
for (var j = 1; j < NewNTPList[i].Item.Count; j++)
{
if (curitem != NewNTPList[i].Item[j].Content[lastdiff])
{
hasdiff = true;
break;
}
}
if (!hasdiff)
{
lastdiff++;
}
}
if (lastdiff > 0)
{
//存在公共部分，需要分离
var needepsilon = false;
//存在重复项，意味着分离出的非公共部分需要包含epsilon
if (lastdiff == minn)
{
needepsilon = true;
}
var newntp = new NonTerminalProductionInfo();
newntp.Name = newntpnameprefix + (newntpid++);
newntp.Item = new List <NonTerminalProductionItemInfo>();
var hadepsilon = false;
//加入非公共部分
foreach (var pitem in NewNTPList[i].Item)
{
if (pitem.Content.Count > lastdiff)
{
var isepsilon = true;
foreach (var item in pitem.Content)
{
if (item != "epsilon")
{
isepsilon = false;
}
}
//判断是否为epsilon项，若是，则设定needepsilon标记留作后面处理
if (isepsilon)
{
if (!hadepsilon)
{
hadepsilon = true;
needepsilon = true;
}
}
else
{
var newcontent = new NonTerminalProductionItemInfo();
newcontent.Content = new List <string>();
for (var j = lastdiff; j < pitem.Content.Count; j++)
{
newcontent.Content.Add(pitem.Content[j]);
}
newntp.Item.Add(newcontent);
}
}
}
//加入epsilon项
if (needepsilon)
{
newntp.Item.Add(new NonTerminalProductionItemInfo {
Content = new string[] { "epsilon" }.ToList()
});
}
//清空原产生式所有项，仅保留公共项，并在最后追加到该新产生式的引用
var content = NewNTPList[i].Item[0];
NewNTPList[i].Item.Clear();
content.Content.RemoveRange(lastdiff, content.Content.Count - lastdiff);
content.Content.Add(newntp.Name);
NewNTPList[i].Item.Add(content);
NewNTPList.Add(newntp);
}
}
}
/// <summary>
/// 消除左递归
/// </summary>
private bool EliminateLeftRecursion(out string ErrorText)
{
ErrorText = "";
var ntplist = ProductionInfo.Production_ParserResult.ntplist;
//首先建立矩阵方程X = XA + B，其中X是1 * n的，A是n * n的，B是1 * n的，n为非终结符的总数
var n = ntplist.Length;
var ntpmap = new Dictionary <string, int>();//非终结符映射表
var X = new string[n];
for (var i = 0; i < n; i++)
{
X[i] = ntplist[i].Name;
ntpmap[X[i]] = i;
}
var A = new List <List <string> > [n, n];
var B = new List <string[]> [n];
for (var i = 0; i < n; i++)
{
for (var j = 0; j < n; j++)
{
A[i, j] = null;
}
}
for (var i = 0; i < n; i++)
{
foreach (var item in ntplist[i].Item)
{
var headerindex = 0;
while (headerindex < item.Content.Length && item.Content[headerindex] == "epsilon")
{
headerindex++;
}
if (headerindex >= item.Content.Length)
{
headerindex = item.Content.Length - 1;//全为epsilon，留出一项即可
}
if (ntpmap.ContainsKey(item.Content[headerindex]))
{
//开头为非终结符，表明该项应该属于A矩阵
var line = ntpmap[item.Content[headerindex]];
//第line行第i列表示第i个产生式的第line项
if (A[line, i] == null)
{
A[line, i] = new List <List <string> >();
}
//创建一个新列表，将头非终结符之后的所有的符号全部加入该列表并追加到A矩阵当前项中
var list = new List <string>();
for (var j = headerindex + 1; j < item.Content.Length; j++)
{
list.Add(item.Content[j]);
}
//防止程序崩溃的保护措施
if (list.Count == 0)
{
list.Add("epsilon");
}
A[line, i].Add(list);
}
else
{
//开头为终结符，表示该项应该属于B矩阵
if (B[i] == null)
{
B[i] = new List <string[]>();
}
B[i].Add(item.Content);
}
}
}
//方程转化为X = BZ,Z = I + AZ
//将方程转化为产生式序列
var newntplist = new List <NonTerminalProductionInfo>();
var newntpitemprefex = Production_Parser.SysNamePrefix + "Z_";
var nullZ = new HashSet <string>();
//生成Z产生式
for (var i = 0; i < n; i++)
{
for (var j = 0; j < n; j++)
{
var newntp = new NonTerminalProductionInfo();
newntp.Name = newntpitemprefex + (i + 1) + "_" + (j + 1);
newntp.Item = new List <NonTerminalProductionItemInfo>();
for (var k = 0; k < n; k++)
{
if (A[i, k] != null)
{
foreach (var pitem in A[i, k])
{
var newcontent = new NonTerminalProductionItemInfo();
newcontent.Content = pitem.ToList();
newcontent.Content.Add(newntpitemprefex + (k + 1) + "_" + (j + 1));
newntp.Item.Add(newcontent);
}
}
}
//+ I
if (i == j)
{
newntp.Item.Add(new NonTerminalProductionItemInfo {
Content = new string[] { "epsilon" }.ToList()
});
}
if (newntp.Item.Count == 0)
{
nullZ.Add(newntp.Name);
}
else
{
newntplist.Add(newntp);
}
}
}
//移除所有无效的Z产生式
var updated = true;
while (updated)
{
updated = false;
for (var i = newntplist.Count - 1; i >= 0; i--)
{
for (var j = newntplist[i].Item.Count - 1; j >= 0; j--)
{
var hasunknownitem = false;
foreach (var item in newntplist[i].Item[j].Content)
{
if (nullZ.Contains(item))
{
hasunknownitem = true;
break;
}
}
if (hasunknownitem)
{
newntplist[i].Item.RemoveAt(j);
updated = true;
}
}
if (newntplist[i].Item.Count == 0)
{
nullZ.Add(newntplist[i].Name);
newntplist.RemoveAt(i);
updated = true;
}
}
}
//产生式选择
for (var i = 0; i < n; i++)
{
var newntp = new NonTerminalProductionInfo();
newntp.Name = X[i];
newntp.Item = new List <NonTerminalProductionItemInfo>();
//遍历B矩阵的每一项，与Z矩阵进行相乘操作
var hasnonnull = false;
for (var j = 0; j < n; j++)
{
if (B[j] != null && !nullZ.Contains(newntpitemprefex + (j + 1) + "_" + (i + 1)))
{
hasnonnull = true;
foreach (var pitem in B[j])
{
var newcontent = new NonTerminalProductionItemInfo();
newcontent.Content = pitem.ToList();
newcontent.Content.Add(newntpitemprefex + (j + 1) + "_" + (i + 1));
newntp.Item.Add(newcontent);
}
}
}
if (!hasnonnull)
{
ErrorText = "[GrammarCompiler_LL_1]:该文法不是LL(1)文法！在进行左递归消除时，对于非终结符\"" + newntp.Name + "\"而言，B矩阵各项全为null，疑似存在循环引用！\n";
return(false);
}
newntplist.Add(newntp);
}
//删除多余产生式，采用从开始符号的引用分析方法
var visited = new Dictionary <string, bool>();
for (var i = 0; i < newntplist.Count; i++)
{
visited[newntplist[i].Name] = false;
ntpmap[newntplist[i].Name] = i;
}
var queue = new Queue <string>();
queue.Enqueue(StartSymbol);
visited[StartSymbol] = true;
while (queue.Count > 0)
{
var curntp = queue.Dequeue();
foreach (var pitem in newntplist[ntpmap[curntp]].Item)
{
foreach (var item in pitem.Content)
{
if (visited.ContainsKey(item) && !visited[item])
{
visited[item] = true;
queue.Enqueue(item);
}
}
}
}
for (var i = newntplist.Count - 1; i >= 0; i--)
{
if (!visited[newntplist[i].Name])
{
newntplist.RemoveAt(i);
}
}
NewNTPList = newntplist;
return(true);
}
