词法分析器设计与实现代码

#include <iostream>

#include<string>

using namespace std;         //VC命名空间

#define  MAX 22          

char ch =' ';

string key[15]={"begin","end","if","then","else","while","int","float", "char","char","until"};

int Iskey(string c){         //关键字判断

   int i;

   for(i=0;i<MAX;i++) {

      if(key[i].compare(c)==0) return 1;

       } 

    return 0;

}

int IsLetter(char c) {        //判断是否为字母

    if(((c<='z')&&(c>='a'))||((c<='Z')&&(c>='A'))) return 1;

    else return 0;

}

int IsDigit(char c){          //判断是否为数字

     if(c>='0'&&c<='9') return 1;

     else return 0;

}

void analyse(FILE *fpin){                //定义文件指针

    string arr="";          

    while((ch=fgetc(fpin))!=EOF) {     //EOF:文件的结尾

            arr="";        

         if(ch==' '||ch=='\t'||ch=='\n'){}     

 

         else if(IsLetter(ch)){

                 while(IsLetter(ch)||IsDigit(ch)) {

                                if((ch<='Z')&&(ch>='A')) ch=ch+32;