官网下载win flex-bison
https://sourceforge.net/projects/winflexbison/

解压

cmd到win——flex的目录


a.l文件内容

```cpp
%{  #include <stdio.h>  #include <stdlib.h>   int count = 0;  
%}   delim [" "\n\t\r]   
whitespace {delim}+   
operator \+|-|\*|\/|:=|>=|<=|#|=|<<|>>|\+\+
reservedWord int|include|main|return|using|if|namespace
delimiter [,\.;\(\)\"]
constant ([0-9])+
identfier [A-Za-z]([A-Za-z][0-9])*  
%%   
{reservedWord} {count++;printf("%d\t(rw,%s)\n",count,yytext);}  
\"[^\"]*\" {count++;printf("%d\t(ct,%s)\n",count,yytext);}
{operator} { count++;printf("%d\t(op,%s)\n",count,yytext); }  
{delimiter} {count++;printf("%d\t(de,%s)\n",count,yytext);}  
{constant} {count++;printf("%d\t(ct,%s)\n",count,yytext);}  
{identfier} {count++;printf("%d\t(id,%s)\n",count,yytext);}   
{whitespace} { /* do    nothing*/ } 
%%int main()
{yyin = fopen("input.txt","r");yylex();fclose(yyin);
}
int yywrap()
{return 1;
}

input.txt文件内容

#include<iostream>
using namespace std;
int main(){cout<<"Hello World!"<<a + b = i++;
}