词法分析可视化MFC

《编译原理》实验一：词法分析

语言：C++
环境：VS2019
实验要求：

1 分析

词法分析是编译过程的第一个阶段。
这个阶段的主要任务是：从左到右一个字符一个字符地读入源程序，对构成源程序的字符流进行扫描和分解，从而识别一个个单词；
（1）获取单词：获取程序字符，并删除注释和过滤空格，本文从输入流中获取单词；
（2）识别单词：识别单词属性；
bool isIdentifier(string s);//标识符
bool isKeywords(string s);//保留字
bool isDigit(string s);//整型数字
bool isOperator(string s);//运算符
bool isOperator(char c);//运算符
string result(string s);//根据传入的参数s产生对应的输出
（3）输出结果：根据已有的单词符号和相应的类别码输出。

2 代码

2.1识别保留字

保留字又称关键字。指在高级语言中已经定义过的字，使用者不能再将这些字作为变量名或过程名使用。

bool isKeywords(string s)//保留字
{
    static vector<string> keyVec = { "main", "int", "float", "double", "char",
        "if", "then","else", "switch", "case", "break", "continue", "while",
        "do", "for" };
    vector<string>::iterator result = find(keyVec.begin(), keyVec.end(), s);//输入的字符串s是否与保留字相等
    if (result != keyVec.end())
        return true;
    else return false;
}

2.2识别标识符

标识符由字母（A-Z，a-z）、数字（0-9）、下划线“_”组成，并且首字符不能是数字。

bool isIdentifier(string s)
{
	if (!isKeywords(s))//标识符不能是保留字
	{
		if ((s[0] >= 'a' && s[0] <= 'z') || (s[0] >= 'A' && s[0] <= 'Z') || s[0] == '_')//标识符由数字、字母、下划线组成，
																					//且不能以数字开头.
		{
			for (int i = 1; i < s.length(); i++)
			{
				if ((s[i] >= 'a' && s[i] <= 'z') || (s[i] >= 'A' && s[i] <= 'Z')
					|| (s[i] >= '0' && s[i] <= '9') || s[i] == '_')
					continue;
				else return false;
			}
			return true;
		}
		return false;
	}
	return false;
}

2.3识别整型数字

bool isDigit(string s)//整型数字,NUM=digit digit*
{
    if (s[0] >= '0' && s[0] <= '9')
    {
        for (int i = 1; i < s.length(); ++i)
            if (s[i] >= '0' && s[i] <= '9')
                continue;
            else return false;
        return true;
    }
    return false;
}

2.4识别运算符

bool isOperator(string s)//运算符
{
    static vector<string> opeVec = { "=","+","-","*","/","<","<=","==","!=",
            ">",">=",";","(",")","?",":","," };
    vector<string>::iterator result = find(opeVec.begin(), opeVec.end(), s);
    if (result != opeVec.end())
        return true;
    else return false;
}

bool isOperator(char c)//运算符
{
    static vector<char> opeVec = { '=','+','-','*','/','<',
        //"<=","==","!=",
        '>',
        //">=",
        ';','(',')','?',':',',' };
    vector<char>::iterator result = find(opeVec.begin(), opeVec.end(), c);
    if (result != opeVec.end())
        return true;
    else return false;
}

3 可视化

本文建立MFC项目实现词法分析可视化

3.1建立MFC项目

打开VS2019，创建新项目，在弹出的菜单搜索MFC

确定项目名称、选择存放位置

应用程序类型，选择“基于对话框”

用户界面功能，勾选“最大化”、“最小化”

点击完成后，如图

3.2创建对话框

删掉对话框的三个控件：

将左侧工具箱中“Edit Control”、“Button”、“Static Text”拖出并摆放如图位置

选中“Button1”，修改“描述文字”为“确定”

同样操作修改：

3.3修改控件属性

（1）左侧编辑框
ID:IDC_EDIT_IN
多行：True
想要返回：True
（2）右侧编辑框
ID:IDC_EDIT_OUT
多行：True
想要返回：True
（3）右击右侧编辑框->添加变量，取名“m_edit”

（4）选中最外层控件，修改最大化框和最小化框为True

3.4封装类

这一过程是封装前面写的词法分析核心代码，加入MFC工程。
右击项目工程名->添加->类

取个名字，确定

此时，在解决方案资源管理器里面，头文件和源文件分别多出了LX.h和LX.cpp
复制LX.h代码

#pragma once

# include<iostream>
# include<string>
# include<fstream>
# include<sstream>//流对象
# include<vector>
# include<map>
using namespace std;
class LX
{
public:
	bool isIdentifier(string s);//标识符
	bool isKeywords(string s);//保留字
	bool isDigit(string s);//整型数字
	bool isOperator(string s);//运算符
	bool isOperator(char c);//运算符
	string result(string s);//根据传入的参数s产生对应的输出
	void main1(string file, string file1);//主处理函数
};

复制LX.cpp代码

#include "pch.h"
#include "LX.h"
using namespace std;
bool LX::isKeywords(string s)//保留字
{
    static vector<string> keyVec = { "main", "int", "float", "double", "char",
        "if", "then","else", "switch", "case", "break", "continue", "while",
        "do", "for" };
    vector<string>::iterator result = find(keyVec.begin(), keyVec.end(), s);//输入的字符串s是否与保留字相等
    if (result != keyVec.end())
        return true;
    else return false;
}

bool LX::isOperator(char c)//运算符
{
    static vector<char> opeVec = { '=','+','-','*','/','<',
        //"<=","==","!=",
        '>',
        //">=",
        ';','(',')','?',':',',' };
    vector<char>::iterator result = find(opeVec.begin(), opeVec.end(), c);
    if (result != opeVec.end())
        return true;
    else return false;
}

bool LX::isDigit(string s)//整型数字,NUM=digit digit*
{
    if (s[0] >= '0' && s[0] <= '9')
    {
        for (int i = 1; i < s.length(); ++i)
            if (s[i] >= '0' && s[i] <= '9')
                continue;
            else return false;
        return true;
    }
    return false;
}

bool LX::isOperator(string s)//运算符
{
    static vector<string> opeVec = { "=","+","-","*","/","<","<=","==","!=",
            ">",">=",";","(",")","?",":","," };
    vector<string>::iterator result = find(opeVec.begin(), opeVec.end(), s);
    if (result != opeVec.end())
        return true;
    else return false;
}

//标识符,,试验要求:ID=letter(letter|digit)*
bool LX::isIdentifier(string s)
{
    if (!isKeywords(s))//标识符不能是保留字
    {
        if ((s[0] >= 'a' && s[0] <= 'z') || (s[0] >= 'A' && s[0] <= 'Z') || s[0] == '_')//标识符由数字、字母、下划线组成，
                                                                                    //且不能以数字开头.
        {
            for (int i = 1; i < s.length(); i++)
            {
                if ((s[i] >= 'a' && s[i] <= 'z') || (s[i] >= 'A' && s[i] <= 'Z')
                    || (s[i] >= '0' && s[i] <= '9') || s[i] == '_')
                    continue;
                else return false;
            }
            return true;
        }
        return false;
    }
    return false;
}

string LX::result(string s)//根据传入的参数s产生对应的输出
{
    //种别码
    //1.标识符
    if (isIdentifier(s))
        return "(标识符--10," + s + ")";

    //2.保留字
    static map<string, string> keyMap;
    keyMap["int"] = "1";
    keyMap["float"] = "2";
    keyMap["if"] = "3";
    keyMap["switch"] = "4";
    keyMap["while"] = "5";
    keyMap["do"] = "6";
    if (isKeywords(s))
        return "(保留字--" + keyMap[s] + "," + s + ")";

    //3.整型常量
    if (isDigit(s))
        return "(整型常量--11," + s + ")";

    //4.运算符
    static map<string, string> opeMap;
    opeMap["="] = "(等号--17，=）";
    opeMap["<"] = "(小于号--20,<)";
    opeMap["<="] = "(小于等于号--21,<=)";
    opeMap["=="] = "(赋值运算符--22，==）";
    opeMap["!="] = "(不等于号--23,!=)";
    opeMap[">"] = "(大于号--24,>)";
    opeMap[">="] = "(大于等于号--25,>=)";
    opeMap[";"] = "(分号--26,;)";
    opeMap["+"] = "(加号--13,+)";
    opeMap["("] = "( 左括号--27,( )";
    opeMap["-"] = "(减号--14,-)";
    opeMap[")"] = "(右括号--28,) )";
    opeMap[">"] = "(大于号--24,>)";
    opeMap["*"] = "(星号--15,*)";
    opeMap["?"] = "(问号--29,?)";
    opeMap["/"] = "(除号--16,/)";
    opeMap[":"] = "(冒号--30,:)";
    opeMap[","] = "(逗号--31,,)";
    if (isOperator(s))
        return opeMap[s];
    return "Error";
}

void LX::main1(string file, string file1)//主处理函数
{
    ifstream input(file);
    ofstream output("Result.txt", ios::out);
    input.close();
    input.open(file);

    string str;
    string words;

    while (getline(input, str)) //读取文件每一次读取一行,遇到EOF结束
    {
        //从输入流中获取单词，需要用到输入流对象，即istringstream
        istringstream strCin(str);
        string s;
        while (strCin >> words)
        {
            //1.首先可以确定的是保留字肯定是单独作为一个单词的
            if (isKeywords(words))
            {
                s = result(words);
                //   cout << s << endl;
                output << s << endl;
                continue;
            }

            //2,对单词进行扫描，肯定是标识符，运算符，逗号分号,数字等等混合在一起的单词
            vector<int> index = { 0 };
            vector<string> mulWords;//将words分解为多个单词
            for (int i = 0; i < words.length(); i++)
            {

                //运算符有两位的，比如"<=",">=","==","!="
                if ((i < words.length() - 1) && isOperator(words[i]) && isOperator(words[i + 1]))
                {
                    //但是要注意只有以上四种两位运算符，比如+-,))就不是,但是))还是要输出),)
                    if (string(words.begin() + i, words.begin() + i + 2) == "<=" ||
                        string(words.begin() + i, words.begin() + i + 2) == ">=" ||
                        string(words.begin() + i, words.begin() + i + 2) == "==" ||
                        string(words.begin() + i, words.begin() + i + 2) == "!=")
                    {
                        index.push_back(i);
                        index.push_back(i + 2);
                        ++i;
                    }
                    else if (isOperator(words[i]))
                    {
                        if (find(index.begin(), index.end(), i) == index.end())
                            index.push_back(i);
                        if (find(index.begin(), index.end(), i + 1) == index.end())
                            index.push_back(i + 1);

                    }
                }
                //逗号，运算符作为分隔
                else if (isOperator(words[i]))
                {
                    if (find(index.begin(), index.end(), i) == index.end())
                        //比如遇到"a,b"这里下标0和1将a分开，1到2将逗号分开，2到3将b分开
                        index.push_back(i);
                    if (find(index.begin(), index.end(), i + 1) == index.end())
                        index.push_back(i + 1);
                }

            }
            for (int i = 0; i < index.size() - 1; i++)
            {
                string rel;
                //比如遇到"<="，需要提取”<=“
                /*if (isOperator(words[index[i]]) && isOperator(words[index[i + 1]]))
                {
                    rel = result(string(words.begin() + index[i], words.begin() + index[i + 2]));
                    ++i;
                }
                else*/
                rel = result(string(words.begin() + index[i], words.begin() + index[i + 1]));

                output << rel << endl;
                //cout << rel << endl;
            }

        }
    }
    output << endl;
    output.close();
    input.close();
}

3.5编写代码

双击对话框中“确定”

在void CLexerDlg::OnBnClickedButton1()里添加代码：

	// TODO: 在此添加控件通知处理程序代码
//定义字符串in存储输入框和输出框的内容
	CString in, out;
	GetDlgItemText(IDC_EDIT_IN, in);
//将输入框内容存入TestData.txt,Result.txt文件中
	CString filename1("Result.txt");
	CStdioFile myFile1;
	CFileException fileException1;
	if (myFile1.Open(filename1, CFile::typeText | CFile::modeCreate | CFile::modeReadWrite), &fileException1)

	{
		myFile1.WriteString(in);
	}
	else
	{
		TRACE("Can't open file %s,error=%u
", filename1, fileException1.m_cause);
	}
	myFile1.Close();


	CString filename("TestData.txt");
	CStdioFile myFile;
	CFileException fileException;
	if (myFile.Open(filename, CFile::typeText | CFile::modeCreate | CFile::modeReadWrite), &fileException)

	{
		myFile.WriteString(in);
	}
	else
	{
		TRACE("Can't open file %s,error=%u
", filename, fileException.m_cause);
	}
	myFile.Close();

//词法分析
	LX a;
	string file = ("TestData.txt");
	string file1 = ("Result.txt");
	a.main1(file,file1);

//将Result.txt文件内容打印到输出框
	//CStdioFile myfile1;
	//CString fileText;
	//CString flieLine;
	ifstream myfile1;
	char buffer[256];
	CString flieLine(_T(""));
	myfile1.open("Result.txt");
	//myfile1.Open(L"Result.txt", CFile::modeReadWrite);
	while (myfile1.getline(buffer, 256, '
'))
	{
		strcat_s(buffer, 256, "
");
		flieLine += buffer;
	}
	
	m_edit.SetWindowText(flieLine);
	myfile1.close();
	

在LexerDlg.cpp前面添加头文件#include "LX.h"
注意:如图，可能会出现红色波浪线，一般是由于修改EditControl的ID，系统没有更新，忽略即可。

运行结果

下载，参考