以下是一个简单的词法分析器

#include <stdio.h>
#include <string.h>
using namespace std ;
int main()
{
	char str[150] ;
//	freopen("C:\\Users\\Lionel\\Desktop\\1.txt","r",stdin) ;
	int row = 1 , cow = 0 ;
	while(gets(str))
	{
		char temp[10] ;
		int index = 0 , i = 0;
		while(i<strlen(str)+1)
		{
			if(str[i] == ‘ ‘ || str[i] == ‘\t‘ || str[i] == ‘\0‘)
			{
				temp[index] = ‘\0‘ ;
				if(!strcmp(temp,"if"))
				{
					printf("IF	(%d,%d)\n",row,i-index+1) ;
				}
				else
				{
					bool flag = false ;
					for(int j = 0 ; j < index ; ++j)
					{
						if(temp[j]<‘0‘ || temp[j]>‘9‘)
						{
							flag = true ;
							break ;
						}
					}
					if(flag)
					{
						printf("ID(%s)	(%d,%d)\n",temp,row,i-index+1) ;
					}
					else
					{
						printf("NUM(%s)	(%d,%d)\n",temp,row,i-index+1) ;
					}
				}
				while((str[i] == ‘ ‘ || str[i] == ‘\t‘) && (str[i+1] == ‘ ‘ || str[i+1] == ‘\t‘))
				{
					++i ;
				}
				index = 0 ;
			}
			else
			{
				temp[index++] = str[i] ;
			}
			++i ;
		}
		row++ ;
	}
	return 0 ;
}