如何使用C#语言实现LR0文法分析器请给出示例代码
以下是一个简单的LR0文法分析器的示例代码:
using System;
using System.Collections.Generic;
class LR0Parser
{
private List<string> productions; // 产生式列表
private Dictionary<string, HashSet<string>> firstSets; // First集合
private Dictionary<string, HashSet<string>> followSets; // Follow集合
private Dictionary<string, Dictionary<string, int>> actionTable; // Action表
private Dictionary<string, Dictionary<string, int>> gotoTable; // Goto表
public LR0Parser(List<string> productions)
{
this.productions = productions;
this.firstSets = new Dictionary<string, HashSet<string>>();
this.followSets = new Dictionary<string, HashSet<string>>();
this.actionTable = new Dictionary<string, Dictionary<string, int>>();
this.gotoTable = new Dictionary<string, Dictionary<string, int>>();
ComputeFirstSets();
ComputeFollowSets();
ComputeActionTable();
ComputeGotoTable();
}
// 计算First集合
private void ComputeFirstSets()
{
// TODO: 实现计算First集合的算法
}
// 计算Follow集合
private void ComputeFollowSets()
{
// TODO: 实现计算Follow集合的算法
}
// 计算Action表
private void ComputeActionTable()
{
// TODO: 实现计算Action表的算法
}
// 计算Goto表
private void ComputeGotoTable()
{
// TODO: 实现计算Goto表的算法
}
// 解析输入串
public bool Parse(string input)
{
Stack<int> stateStack = new Stack<int>();
Stack<string> symbolStack = new Stack<string>();
stateStack.Push(0);
int i = 0;
while (i < input.Length)
{
int state = stateStack.Peek();
string symbol = input[i].ToString();
if (actionTable.ContainsKey(state.ToString()) && actionTable[state.ToString()].ContainsKey(symbol))
{
int action = actionTable[state.ToString()][symbol];
if (action > 0)
{
stateStack.Push(action);
symbolStack.Push(symbol);
i++;
}
else if (action < 0)
{
int productionIndex = -action - 1;
string production = productions[productionIndex];
string[] parts = production.Split(new char[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
for (int j = 0; j < parts.Length - 1; j++)
{
stateStack.Pop();
symbolStack.Pop();
}
int newState = gotoTable[stateStack.Peek().ToString()][parts[0]];
stateStack.Push(newState);
symbolStack.Push(parts[0]);
}
else
{
return true;
}
}
else
{
return false;
}
}
return false;
}
}
class Program
{
static void Main(string[] args)
{
List<string> productions = new List<string>();
productions.Add("S -> E");
productions.Add("E -> E + T");
productions.Add("E -> T");
productions.Add("T -> T * F");
productions.Add("T -> F");
productions.Add("F -> ( E )");
productions.Add("F -> id");
LR0Parser parser = new LR0Parser(productions);
Console.WriteLine(parser.Parse("id + id * id"));
}
}
以上代码仅提供了一个框架,需要根据具体的LR0文法分析算法来实现计算First集合、Follow集合、Action表和Goto表的方法。同时,需要根据具体的文法来修改产生式列表
原文地址: https://www.cveoy.top/t/topic/hdGX 著作权归作者所有。请勿转载和采集!