SLR1 分析器实现 - SLR1 文法分析表构造
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 Table[][] GET_ANA()
{
SLRAnaly();
RStr_ANA += '\r\nSLR1分析表:\r\n ';
int i;
for (i = 0; i < Echar.Count; i++)
{
RStr_ANA += Echar[i].ToString() + ' ';
}
for (i = 0; i < Nchar.Count; i++)
{
RStr_ANA += Nchar[i].ToString() + ' ';
}
RStr_ANA += '\r\n';
for (i = 0; i < proitemset.Count; i++)
{
RStr_ANA += i.ToString() + ' ';
for (int j = 0; j < Echar.Count + Nchar.Count; j++)
{
if (SLRAna[i][j].error)
{
RStr_ANA += ' ' + ' ';
}
else if (i == 0 && j == Echar.Count - 1)
{
RStr_ANA += 'ACC' + ' ';
}
else if (SLRAna[i][j].type != 'N')
{
RStr_ANA += SLRAna[i][j].type.ToString() + SLRAna[i][j].id.ToString() + ' ';
}
else
RStr_ANA += SLRAna[i][j].id.ToString() + ' ';
}
RStr_ANA += '\r\n';
}
return SLRAna;
}
public void SLRAnaly()
{
//构造First集
foreach (char c in Nchar)
{
first.Add(c, new HashSet<char>());
}
foreach (char c in Echar)
{
first.Add(c, new HashSet<char>() { c });
}
bool changed = true;
while (changed)
{
changed = false;
foreach (SLRNode node in SLRproNum)
{
int oldCount = first[node.Left].Count;
if (node.Right == 'ε')
{
first[node.Left].Add('ε');
}
else
{
foreach (char c in node.Right)
{
if (first.ContainsKey(c))
{
first[node.Left].UnionWith(first[c]);
if (!first[c].Contains('ε'))
{
break;
}
}
else
{
first[node.Left].Add(c);
break;
}
}
}
if (first[node.Left].Count > oldCount)
{
changed = true;
}
}
}
//构造Follow集
foreach (char c in Nchar)
{
follow.Add(c, new HashSet<char>());
}
follow[SLRproNum[0].Left].Add('#');
changed = true;
while (changed)
{
changed = false;
foreach (SLRNode node in SLRproNum)
{
for (int i = 0; i < node.Right.Length; i++)
{
if (Nchar.Contains(node.Right[i]))
{
HashSet<char> temp = new HashSet<char>();
if (i == node.Right.Length - 1)
{
temp.UnionWith(follow[node.Left]);
}
else
{
for (int j = i + 1; j < node.Right.Length; j++)
{
if (first.ContainsKey(node.Right[j]))
{
temp.UnionWith(first[node.Right[j]]);
if (!first[node.Right[j]].Contains('ε'))
{
break;
}
}
else
{
temp.Add(node.Right[j]);
break;
}
}
if (temp.Contains('ε'))
{
temp.Remove('ε');
temp.UnionWith(follow[node.Left]);
}
}
int oldCount = follow[node.Right[i]].Count;
follow[node.Right[i]].UnionWith(temp);
if (follow[node.Right[i]].Count > oldCount)
{
changed = true;
}
}
}
}
}
//构造项目集
SLRobjNum.Add(new SLRNode(SLRproNum[0].Left, '.' + SLRproNum[0].Right));
proitemset.Add(new SLRitemsets() { Container = new List<int>() { 0 }, LookAhead = new HashSet<char>() { '#' } });
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++)
{
HashSet<char> lookAhead = new HashSet<char>();
foreach (int index in proitemset[i].Container)
{
SLRNode node = SLRobjNum[index];
if (node.Right.IndexOf('.') < node.Right.Length - 1 && node.Right[node.Right.IndexOf('.') + 1] == Echar[j])
{
lookAhead.Add('#');
}
if (node.Right.IndexOf('.') < node.Right.Length - 1 && Nchar.Contains(node.Right[node.Right.IndexOf('.') + 1]))
{
foreach (char c in follow[node.Right[node.Right.IndexOf('.') + 1]])
{
lookAhead.Add(c);
}
}
}
HashSet<int> temp = Goto(proitemset[i].Container, Echar[j]);
if (temp.Count > 0)
{
for (int k = 0; k < proitemset.Count; k++)
{
if (proitemset[k].Container.Count == temp.Count && proitemset[k].Container.All(temp.Contains))
{
proitemset[i].LookAhead.UnionWith(lookAhead);
dfa[Pindex++] = new DFA(i, Echar[j], k, lookAhead);
flag = true;
break;
}
}
if (!flag)
{
proitemset.Add(new SLRitemsets() { Container = temp, LookAhead = lookAhead });
dfa[Pindex++] = new DFA(i, Echar[j], proitemset.Count - 1, lookAhead);
flag = true;
}
}
}
}
}
//构造SLR分析表
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++)
{
SLRAna[i][j] = new Table();
}
}
for (int i = 0; i < dfa.Length; i++)
{
if (dfa[i].symbol != 'ε')
{
if (Echar.Contains(dfa[i].symbol))
{
SLRAna[dfa[i].from][Echar.IndexOf(dfa[i].symbol)] = new Table('S', dfa[i].to);
}
else
{
SLRAna[dfa[i].from][Echar.Count + Nchar.IndexOf(dfa[i].symbol)] = new Table('S', dfa[i].to);
}
}
else
{
for (int j = 0; j < proitemset[dfa[i].from].LookAhead.Count; j++)
{
if (Echar.Contains(proitemset[dfa[i].from].LookAhead.ElementAt(j)))
{
SLRAna[dfa[i].from][Echar.IndexOf(proitemset[dfa[i].from].LookAhead.ElementAt(j))] = new Table('R', proitemset[dfa[i].from].Container[0]);
}
else
{
SLRAna[dfa[i].from][Echar.Count + Nchar.IndexOf(proitemset[dfa[i].from].LookAhead.ElementAt(j))] = new Table('R', proitemset[dfa[i].from].Container[0]);
}
}
}
}
for (int i = 0; i < proitemset.Count; i++)
{
for (int j = 0; j < SLRproNum.Count; j++)
{
if (SLRobjNum[proitemset[i].Container[0]].Right.IndexOf('.') == SLRobjNum[proitemset[i].Container[0]].Right.Length - 1 && SLRobjNum[proitemset[i].Container[0]].Left == SLRproNum[j].Left)
{
for (int k = 0; k < proitemset[i].LookAhead.Count; k++)
{
if (Echar.Contains(proitemset[i].LookAhead.ElementAt(k)))
{
SLRAna[i][Echar.IndexOf(proitemset[i].LookAhead.ElementAt(k))] = new Table('R', j + 1);
}
else
{
SLRAna[i][Echar.Count + Nchar.IndexOf(proitemset[i].LookAhead.ElementAt(k))] = new Table('R', j + 1);
}
}
}
}
}
}
public HashSet<int> Goto(List<int> I, char symbol)
{
HashSet<int> res = new HashSet<int>();
for (int i = 0; i < I.Count; i++)
{
SLRNode node = SLRobjNum[I[i]];
if (node.Right.IndexOf('.') < node.Right.Length - 1 && node.Right[node.Right.IndexOf('.') + 1] == symbol)
{
res.Add(SLRobjNum.IndexOf(new SLRNode(node.Left, node.Right.Substring(0, node.Right.IndexOf('.')) + symbol + '.' + node.Right.Substring(node.Right.IndexOf('.') + 2))));
}
}
return res;
}
//判断项目是否存在于项目集合中
public bool isnexist(List<int> I, int j)
{
if (I.Contains(j))
return true;
else
return false;
}
//判断是否是终结符
public bool isFinalsymbol(char ch)
{
if (Echar.Contains(ch))
return true;
else
return false;
}
原文地址: https://www.cveoy.top/t/topic/f0N1 著作权归作者所有。请勿转载和采集!