Compiler_词法分析_直接转向法

来源：互联网发布：复制linux系统编辑：程序博客网时间：2024/05/29 14:05
本文出自：blog.csdn.net/svitter
依据上述转换图，写出直接转向代码：
//============================================================================// Name        : Comlier.cpp// Author      : vit// Version     :// Copyright   : Your copyright notice// Description : Hello World in C++, Ansi-style//============================================================================#include <iostream>#include <string.h>using namespace std;bool confirm;int status;int no;bool JudgeNum(char &a){    if(a >= '0' && a <= '9')        return true;    else        return false;}void analysis(string &a){    if(status == 0)    {        if(a[no] == '.')        {            status = 6;            no ++;            analysis(a);        }        else if(JudgeNum(a[no]))        {            status = 1;            no ++;            analysis(a);        }        else        {            confirm = false;//            cout << status;            return;        }    }    else if(status == 1)    {        if(JudgeNum(a[no]) || a[no] == '.')        {            status = 2;            no++;            analysis(a);        }        else if(a[no] == 'E'|| a[no] == 'e')        {            status = 5;            no++;            analysis(a);        }        else        {            confirm = false;//            cout << status;            return ;        }    }    else if(status == 2)    {        if(JudgeNum(a[no]))        {            status = 2;            no++;            analysis(a);        }        else if(a[no] == 'E'|| a[no] == 'e')        {            status = 3;            no++;            analysis(a);        }        else        {            confirm = true;//            cout << status;            return;        }    }    else if(status == 3)    {        if(a[no] == '+' || a[no] == '-')        {            status = 4;            no++;            analysis(a);        }        else        {            confirm = false;//            cout << status;            return;        }    }    else if(status == 4)    {        if(JudgeNum(a[no]))        {            status = 5;            no++;            analysis(a);        }        else        {            confirm = false;//            cout << status;            return;        }    }    else if(status == 5)    {        if(JudgeNum(a[no]))        {            status = 5;            no++;            analysis(a);        }        else        {            confirm = true;//            cout << status;            return;        }    }    else if(status == 6)    {        if(JudgeNum(a[no]))        {            status = 2;            no++;            analysis(a);        }        else        {            confirm = false;//            cout << status;            return;        }    }    else        cout << "status error." << endl;}int main(){    string a;    while(cin >> a)    {        confirm = false;        status = 0;        no = 0;        analysis(a);        if(confirm)            cout << "yes" << endl;        else            cout << "no" << endl;    }}
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