SLR(1) 分析表构建: 代码实现及优化
class SLR
{
//产生式结点类
public class SLRNode
{
public string Left;
public string Right;
public SLRNode(string Left, string Right)
{
this.Left = Left;
this.Right = Right;
}
}
//项目集类
public class SLRitemsets
{
public List
//DFA结点
public struct DFA
{
public int from;
public char symbol;
public int to;
public DFA(int from, char symbol, int to)
{
this.from = from;
this.symbol = symbol;
this.to = to;
}
}
//分析表 结点
public class Table
{
public bool error;//是否为ERROR
public char type;//结点类型
public int id;//数值
public Table()
{
this.error = true;
}
public Table(char type, int id)
{
this.type = type;
this.id = id;
this.error = false;
}
}
public DFA[] dfa = new DFA[100];
public int Pindex = 0; //dfa数组指针
public Table[][] SLRAna;//分析表
public List<SLRNode> SLRproNum = new List<SLRNode>(50);//产生式 列表
public List<SLRNode> SLRobjNum = new List<SLRNode>(50);//项目 列表
public List<SLRitemsets> proitemset = new List<SLRitemsets>(100);//项目集合
public List<int> Gy_obj = new List<int>(50);//归约项目序号集合
public List<int> Gy_itemset = new List<int>(50);//含有归约项目的集合的序号 的集合
public List<char> Nchar = new List<char>(50);//非终结符集合
public List<char> Echar = new List<char>(50);//终结符集合
public void Buildprod(string str)
{
SLRNode SLr;
int i = 0;
string left = "";
string right = "";
left += "S'";
right += str[0];
SLr = new SLRNode(left, right);//拓广文法开始
SLRproNum.Add(SLr);
while (i < str.Length)
{
left = right = "";//还原
int j = i;
while (i < str.Length && str[i] != '\r' && str[i] != '\n')//换行符‘\r\n’
{
if (str[i] == ' ')
{
i++;
continue;
}
if (str[i] == '|') // 遇到“|”可构造一条产生式
{
SLr = new SLRNode(left, right);
SLRproNum.Add(SLr);
right = ""; //产生式左边相同 右边重新积累
i++; //跳过“|”
continue;
}
if ((i - j) == 0)
{
if (!exist(Nchar, str[i]))//如果非终结符集合中不存在str[i],加入Nchar 产生式左边 只有非终结符 不必判断终结符
Nchar.Add(str[i]);
left += str[i++];
}
else if (i - j <= 2)
i++;
else
{
if (isFinalsymbol(str[i]) && !exist(Nchar, str[i]))//如果非终结符集合中不存在str[i],加入Nchar isfinalsymbol 非终结符返回T 终结符返回F
Nchar.Add(str[i]);
else if (!isFinalsymbol(str[i]) && !exist(Echar, str[i]))//产生式右边 需要判断终结符
Echar.Add(str[i]);
right += str[i++];
}
}//while
i++;//跳过换行符
if (left != "" && right != "")
{
SLr = new SLRNode(left, right);//构造每一行最后一个产生式，不存在"|"时就是该行产生式本身
SLRproNum.Add(SLr);
}
}//while
Echar.Add('#');
//构造项目 对产生式集合LRproNum中的所有产生式都循环插'.'
SLRNode Lobj;
for (i = 0; i < SLRproNum.Count; i++)
{
left = "";
right = "";
for (int j = 0; j <= SLRproNum[i].Right.Length; j++)//j可以等于length 项目共length+1个
{
left = SLRproNum[i].Left;
right = CreObj(SLRproNum[i].Right, j);//在第j个位置插入'.'
if (j == SLRproNum[i].Right.Length && SLRobjNum.Count != 1)
{
//在产生式最后的位置插入. 即为归约项目 项目集中1号位置为接受项目
Gy_obj.Add(SLRobjNum.Count);//归约项目在项目集中的序号 不用+1 本身就是从0开始的
}
Lobj = new SLRNode(left, right);
SLRobjNum.Add(Lobj);
left = "";//还原
right = "";
}
}
Creteitemsets();//项目集
RStr_obitemset += "\r\n项目集构建：\r\n";
for (int j = 0; j < proitemset.Count; j++)
{
RStr_obitemset += 'I' + j.ToString() + ':' + "\r\n";
for (i = 0; i < proitemset[j].Container.Count; i++)
{
RStr_obitemset += SLRobjNum[proitemset[j].Container[i]].Left.ToString() + "->" + SLRobjNum[proitemset[j].Container[i]].Right.ToString() + "\r\n";
}
}
}
//求项目集
public void Creteitemsets()
{
List<int> lr_item = new List<int>(100);//记录项目的序号
lr_item.Add(0);
lr_item = Closure(lr_item);//构造初始项目集 求闭包
SLRitemsets LR_C = new SLRitemsets();
LR_C.Container = lr_item;//集合----项目集序号的集合
proitemset.Add(LR_C);//集合的集合----存放项目集序号集合 的集合
for (int i = 0; i < proitemset.Count; i++)//整体集合中 第i个项目集
{
proitemset[i].Container.Sort();//排序由小到大 后面用于判断是否存在的比较
int[] flag = new int[proitemset[i].Container.Count];
for (int fi = 0; fi < proitemset[i].Container.Count; fi++)//标志位，用来判断该序号是否已经构造
{
flag[fi] = 0;
}
for (int j = 0; j < proitemset[i].Container.Count; j++)//第i个项目集的第j个项目
{
if (flag[j] == 1)//如果已经访问过 就不再构造 找下一个项目
continue;
int index = proitemset[i].Container[j];
for (int pi = 0; pi < SLRobjNum[index].Right.Length - 1; pi++)//length-1是避免匹配到.在最后的规约项目
{
if (SLRobjNum[index].Right[pi] == '.')
{
List<int> lr2_club = new List<int>(100);//记录项目的序号
char symbol = SLRobjNum[index].Right[pi + 1];//记录.a转移状态a.的符号a
lr2_club.Add((index + 1));//如果遇到.a形式的项目序号为index 那么项目a.的序号为index+1
for (int m1 = j + 1; m1 < proitemset[i].Container.Count; m1++)
{
//在第i个项目集中找到了可以移动的.：.a 重新遍历第i个项目集j项目之后的 找到同样可以移动a的项目集
int index2 = proitemset[i].Container[m1];
for (int m2 = 0; m2 < SLRobjNum[index2].Right.Length - 1; m2++)
{
if (SLRobjNum[index2].Right[m2] == '.' && SLRobjNum[index2].Right[m2 + 1] == symbol)
{
flag[m1] = 1;//标记位置为1 已经访问 之后不再访问
lr2_club.Add(index2 + 1);
}
}
}
lr2_club = Closure(lr2_club);//求闭包
int value = isexist(lr2_club);
if (value == -1)//-1表示不存在相同的
{
for (int m3 = 0; m3 < Gy_obj.Count; m3++)
{
if (isnexist(lr2_club, Gy_obj[m3]))
{
Gy_itemset.Add(proitemset.Count);
}
}
SLRitemsets LR_C2 = new SLRitemsets();
dfa[Pindex++] = new DFA(i, symbol, proitemset.Count);//count不用加1 本身从0开始
LR_C2.Container = lr2_club;
proitemset.Add(LR_C2);
}
else
{
dfa[Pindex++] = new DFA(i, symbol, value);
}
break;
}
}
}
}
}
//分析表
public void SLRAnaly()
{
//获取所有终结符和非终结符
List<char> terminals = new List<char>();
List<char> nonterminal = new List<char>();
foreach (var item in Echar)
{
terminals.Add(item);
}
foreach (var item in Nchar)
{
nonterminal.Add(item);
}
//构造LL(1)分析表
LL1Analy isLL_1_ = new LL1Analy(SLRproNum);
isLL_1_.getfirst();
isLL_1_.getfollow();
//构造DFA
buildDFA();
//构造分析表
buildtable();
}
//构造DFA
public void buildDFA()
{
//获取所有终结符和非终结符
List<char> terminals = new List<char>();
List<char> nonterminal = new List<char>();
foreach (var item in Echar)
{
terminals.Add(item);
}
foreach (var item in Nchar)
{
nonterminal.Add(item);
}
//初始化DFA
int stateCount = proitemset.Count;
for (int i = 0; i < stateCount; i++)
{
for (int j = 0; j < terminals.Count; j++)
{
dfa[Pindex++] = new DFA(i, terminals[j], -1);
}
for (int j = 0; j < nonterminal.Count; j++)
{
dfa[Pindex++] = new DFA(i, nonterminal[j], -1);
}
}
//填充DFA
foreach (var item in proitemset)
{
int i = proitemset.IndexOf(item);
foreach (var symbol in terminals)
{
List<int> nextState = Goto(item.Container, symbol);
if (nextState.Count > 0)
{
int j = proitemset.IndexOf(new SLRitemsets() { Container = nextState });
dfa[i * terminals.Count + terminals.IndexOf(symbol)].to = j;
}
}
foreach (var symbol in nonterminal)
{
List<int> nextState = Goto(item.Container, symbol);
if (nextState.Count > 0)
{
int j = proitemset.IndexOf(new SLRitemsets() { Container = nextState });
dfa[stateCount * terminals.Count + i * nonterminal.Count + nonterminal.IndexOf(symbol)].to = j;
}
}
}
}
//求GOTO(I, X)
public List<int> Goto(List<int> I, char X)
{
List<int> J = new List<int>();
foreach (var item in I)
{
if (item < SLRobjNum.Count)
{
SLRNode node = SLRobjNum[item];
int dotIndex = node.Right.IndexOf('.');
if (dotIndex < node.Right.Length - 1 && node.Right[dotIndex + 1] == X)
{
SLRNode newNode = new SLRNode(node.Left, node.Right.Substring(0, dotIndex) + X + '.' + node.Right.Substring(dotIndex + 2));
int index = SLRobjNum.IndexOf(newNode);
if (index >= 0 && !J.Contains(index))
{
J.Add(index);
}
}
}
}
return Closure(J);
}
//求闭包
public List<int> Closure(List<int> I)
{
List<int> J = new List<int>(I);
for (int i = 0; i < J.Count; i++)
{
if (J[i] < SLRproNum.Count)
{
SLRNode node = SLRproNum[J[i]];
int dotIndex = node.Right.IndexOf('.');
if (dotIndex < node.Right.Length - 1)
{
char X = node.Right[dotIndex + 1];
List<SLRNode> nodes = new List<SLRNode>();
foreach (var item in SLRproNum)
{
if (item.Left == X.ToString())
{
nodes.Add(new SLRNode(item.Left, '.' + item.Right));
}
}
foreach (var item in nodes)
{
int index = SLRobjNum.IndexOf(item);
if (index >= 0 && !J.Contains(index))
{
J.Add(index);
}
}
}
}
}
return J;
}
//构造分析表
public void buildtable()
{
//获取所有终结符和非终结符
List<char> terminals = new List<char>();
List<char> nonterminal = new List<char>();
foreach (var item in Echar)
{
terminals.Add(item);
}
foreach (var item in Nchar)
{
nonterminal.Add(item);
}
SLRAna = new Table[proitemset.Count][];
for (int i = 0; i < proitemset.Count; i++)
{
SLRAna[i] = new Table[terminals.Count + nonterminal.Count];
for (int j = 0; j < terminals.Count + nonterminal.Count; j++)
{
SLRAna[i][j] = new Table();
}
}
//构造分析表
List<string> strings = new List<string>();
for (int i = 0; i < proitemset.Count; i++)
{
strings = new List<string>();
//对每个状态经过终结符的情况进行判断
for (int j = 0; j < terminals.Count; j++)
{
char symbol = terminals[j];
int flag = 0;
//包含移进项的
if (dfa[i * terminals.Count + j].to != -1)
{
SLRAna[i][j] = new Table('S', dfa[i * terminals.Count + j].to);
flag = 1;
}
else
{
for (int k = 0; k < Gy_itemset.Count; k++)
{
if (Gy_itemset[k] == i)
{
for (int m = 0; m < Gy_obj.Count; m++)
{
if (proitemset[i].Container.Contains(Gy_obj[m]) && isLL_1_.follow.getfollows()[SLRobjNum[Gy_obj[m]].Left].Contains(symbol))
{
SLRAna[i][j] = new Table('r', m);
flag = 1;
break;
}
}
}
if (flag == 1)
{
break;
}
}
}
if (flag == 0)
{
SLRAna[i][j] = new Table();
}
}
//对每个状态经过非终结符的情况进行判断
for (int j = 0; j < nonterminal.Count; j++)
{
char symbol = nonterminal[j];
int flag = 0;
if (dfa[terminals.Count * proitemset.Count + i * nonterminal.Count + j].to != -1)
{
SLRAna[i][terminals.Count + j] = new Table('S', dfa[terminals.Count * proitemset.Count + i * nonterminal.Count + j].to);
flag = 1;
}
if (flag == 0)
{
SLRAna[i][terminals.Count + j] = new Table();
}
}
}
//输出分析表
Console.WriteLine("分析表：");
for (int i = 0; i < proitemset.Count; i++)
{
Console.Write("状态" + i + "：");
for (int j = 0; j < terminals.Count + nonterminal.Count; j++)
{
if (SLRAna[i][j].error)
{
Console.Write(" ");
}
else
{
Console.Write(SLRAna[i][j].type + SLRAna[i][j].id + " ");
}
}
Console.WriteLine();
}
}
//判断非终结符
public bool isFinalsymbol(char c)
{
if (c >= 'A' && c <= 'Z')
{
return true;
}
return false;
}
//判断是否存在
public bool exist(List<char> list, char c)
{
for (int i = 0; i < list.Count; i++)
{
if (list[i] == c)
{
return true;
}
}
return false;
}
//在产生式右边插入'.'
public string CreObj(string str, int pos)
{
string str_result = "";
if (pos == 0)
{
str_result += "." + str;
return str_result;
}
if (pos > str.Length)
{
return null;
}
str_result += str.Substring(0, pos) + "." + str.Substring(pos, str.Length - pos);
return str_result;
}
//判断项目集是否存在
public int isexist(List<int> I)
{
for (int i = 0; i < proitemset.Count; i++)
{
if (proitemset[i].Container.Count == I.Count && isnexist(proitemset[i].Container, I[0]))
{
return i;
}
}
return -1;
}
//判断项目序号是否存在
public bool isnexist(List<int> I, int num)
{
for (int i = 0; i < I.Count; i++)
{
if (I[i] == num)
{
return true;
}
}
return false;
}
原文地址: https://www.cveoy.top/t/topic/f1Ro 著作权归作者所有。请勿转载和采集!