SLR1 分析器构造：基于 LR0 分析器的改进
public class SLRNode
{
public string Left;
public string Right;
public HashSet
//DFA结点
public struct DFA
{
public int from;
public char symbol;
public int to;
public HashSet<char> LookAhead;
public DFA(int from, char symbol, int to, HashSet<char> LookAhead)
{
this.from = from;
this.symbol = symbol;
this.to = to;
this.LookAhead = LookAhead;
}
}
//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 Analyze Jz;
public bool Success = false;
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
Dictionary<char, HashSet<char>> first = new Dictionary<char, HashSet<char>>();//非终结符的First集
Dictionary<char, HashSet<char>> follow = new Dictionary<char, HashSet<char>>();//非终结符的Follow集
public string RStr = '';
public string RStr_obitemset = '';//输出返回
public string RStr_DFA = '';
public string RStr_ANA = '';
public void CreateDFA()
{
RStr_DFA += '\r\nSLR1分析器DFA:\r\n';
RStr_DFA += '状态|';
foreach (char c in Echar)
{
RStr_DFA += c + '|';
}
foreach (char c in Nchar)
{
RStr_DFA += c + '|';
}
RStr_DFA += '\r\n';
for (int i = 0; i < Pindex; i++)
{
RStr_DFA += i + ' |';
for (int j = 0; j < Echar.Count + Nchar.Count; j++)
{
if (dfa[i].to == -1)
{
RStr_DFA += ' |';
}
else
{
if (dfa[i].symbol == (j < Echar.Count ? Echar[j] : Nchar[j - Echar.Count]))
{
RStr_DFA += dfa[i].to + ',' + string.Join('', dfa[i].LookAhead) + '|';
}
else
{
RStr_DFA += ' |';
}
}
}
RStr_DFA += '\r\n';
}
}
public void CreateItemsets()
{
//初始化第一个项目集
SLRitemsets itemset0 = new SLRitemsets();
itemset0.Container.Add(0);
itemset0.LookAhead.Add('#');
itemset0 = Closure(itemset0);
proitemset.Add(itemset0);
//构造所有项目集
bool flag = true;
while (flag)
{
flag = false;
for (int i = 0; i < proitemset.Count; i++)
{
for (int j = 0; j < Echar.Count + Nchar.Count; j++)
{
char symbol = j < Echar.Count ? Echar[j] : Nchar[j - Echar.Count];
HashSet
public SLRitemsets Closure(SLRitemsets itemset)
{
for (int index = 0; index < itemset.Container.Count; index++)//遍历该集合中的所有序号 初始序号就是拓广文法的0 下面的ADD步骤中会扩大他的内容
for (int i = 0; i < SLRobjNum[itemset.Container[index]].Right.Length - 1; i++)//遍历第index序号项目右侧字符串 找到.A结构
{
if (SLRobjNum[itemset.Container[index]].Right[i] == '.' && isFinalsymbol(SLRobjNum[itemset.Container[index]].Right[i + 1]))
{
for (int j = 0; j < SLRobjNum.Count; j++)//遍历所有项目，找到以A开头的.a
{
if (isnexist(itemset.Container, j))
continue;
if (SLRobjNum[j].Left == SLRobjNum[itemset.Container[index]].Right[i + 1].ToString() && SLRobjNum[j].Right[0] == '.')
{
itemset.Container.Add(j);//ADD：在项目集（序号集合）中加入新成员
foreach (char c in follow[SLRobjNum[itemset.Container[index]].Right[i + 1]])
{
if (!itemset.LookAhead.Contains(c))
{
itemset.LookAhead.Add(c);
}
}
}
}
}
}
return itemset;
}
public void CreateSLRTable()
{
CreateItemsets();
CreateDFA();
SLRAna = new Table[proitemset.Count][];
for (int i = 0; i < proitemset.Count; i++)
{
SLRAna[i] = new Table[Echar.Count + Nchar.Count];
for (int j = 0; j < Echar.Count + Nchar.Count; j++)
{
char symbol = j < Echar.Count ? Echar[j] : Nchar[j - Echar.Count];
int nextState = -1;
HashSet<char> lookAhead = new HashSet<char>();
foreach (DFA d in dfa)
{
if (d.from == i && d.symbol == symbol)
{
nextState = d.to;
lookAhead.UnionWith(d.LookAhead);
break;
}
}
if (nextState == -1)
{
SLRAna[i][j] = new Table();
}
else if (Gy_obj.Contains(nextState))
{
SLRAna[i][j] = new Table('R', Gy_obj.IndexOf(nextState) + 1);
}
else if (proitemset[nextState].LookAhead.Contains('#'))
{
SLRAna[i][j] = new Table('A', 0);
}
else
{
SLRAna[i][j] = new Table('S', nextState);
}
}
foreach (int index in Gy_itemset)
{
if (proitemset[index].Container.Contains(i))
{
foreach (char c in proitemset[index].LookAhead)
{
if (Echar.IndexOf(c) >= 0)
{
SLRAna[i][Echar.IndexOf(c)] = new Table('R', Gy_obj.IndexOf(index) + 1);
}
else if (c == '#')
{
SLRAna[i][Nchar.Count - 1] = new Table('R', Gy_obj.IndexOf(index) + 1);
}
}
}
}
}
Success = true;
}
public void CreateFirst()
{
foreach (char c in Nchar)
{
first[c] = new HashSet<char>();
}
bool flag = true;
while (flag)
{
flag = false;
foreach (SLRNode node in SLRproNum)
{
if (node.Right.Length > 0)
{
if (Echar.Contains(node.Right[0]))
{
if (first[node.Left].Add(node.Right[0]))
{
flag = true;
}
}
else
{
bool canEpsilon = true;
foreach (char c in node.Right)
{
if (Echar.Contains(c))
{
if (first[node.Left].Add(c))
{
flag = true;
}
if (!first[c].Contains('ε'))
{
canEpsilon = false;
break;
}
}
else
{
if (first[node.Left].UnionWith(first[c]))
{
flag = true;
}
if (!first[c].Contains('ε'))
{
canEpsilon = false;
break;
}
}
}
if (canEpsilon && first[node.Left].Add('ε'))
{
flag = true;
}
}
}
}
}
}
public void CreateFollow()
{
foreach (char c in Nchar)
{
follow[c] = new HashSet<char>();
}
follow[SLRproNum[0].Left].Add('#');
bool flag = true;
while (flag)
{
flag = false;
foreach (SLRNode node in SLRproNum)
{
for (int i = 0; i < node.Right.Length; i++)
{
if (Nchar.Contains(node.Right[i]))
{
if (i == node.Right.Length - 1)
{
if (follow[node.Right[i]].UnionWith(follow[node.Left]))
{
flag = true;
}
}
else
{
bool canEpsilon = true;
for (int j = i + 1; j < node.Right.Length; j++)
{
if (Echar.Contains(node.Right[j]))
{
if (follow[node.Right[i]].Add(node.Right[j]))
{
flag = true;
}
canEpsilon = false;
break;
}
else
{
if (follow[node.Right[i]].UnionWith(first[node.Right[j]]))
{
flag = true;
}
if (!first[node.Right[j]].Contains('ε'))
{
canEpsilon = false;
break;
}
}
}
if (canEpsilon)
{
if (follow[node.Right[i]].UnionWith(follow[node.Left]))
{
flag = true;
}
}
}
}
}
}
}
}
//判断是否是终结符
public bool isFinalsymbol(char symbol)
{
return Echar.Contains(symbol);
}
//判断项目是否存在于项目集合中
public bool isnexist(List<int> I, int i)
{
foreach (int index in I)
{
if (index == i)
{
return false;
}
}
return true;
}
原文地址: https://www.cveoy.top/t/topic/f0Ob 著作权归作者所有。请勿转载和采集!