input.txt

%{
#include<iostream>
#include<string>
#include<stdio.h>
#include<fstream>
using namespace std;
%}
digit	[0-9]
nature  [1-9]
letter	[a-zA-Z]
id	{letter}[{letter}|{digit}]^
integer	{digit}{digit}^
floatnum	[{digit}|{digit}^].[{digit}|{digit}^]
port	${digit}^
%%
"auto"		{return "AUTO";}
"break"		{return "BREAK";}
"case"		{return "CASE"; }
"char"		{return "CHAR"; }
"const"		{return "CONST";}
"continue"	{return "CONTINUE";}
"default"	{return "DEFAULT"; }
"do"		{return "DO";}
"double"	{return "DOUBLE"; }
"enum"		{return "ENUM"; }
"else"		{return "ELSE";}
"float"		{return "FLOAT"; }
"for"		{return "FOR";}
"if"		{return "IF";}
"int"		{return "INT";}
"long"		{return "LONG";}
"return"	{return "RETURN";}
"short"		{return "SHORT";}
"sizeof"	{return "SIZEOF";}
"struct"	{return "STRUCT"; }
"switch"	{return "SWITCH"; }
"typedef"	{return "TYPEDEF";}
"union"		{return "UNION"; }
"unsigned"	{return "UNSIGNED"; }
"void"		{return "VOID";}
"while"		{return "WHILE";}
{id}		{yylval=install_id();return "IDENTIFIER";}
{port}		{yylval=convert_port();return "PORT";}
{floatnum}	{yylval=convert_float();return "FLOATNUM";}
{integer}	{yylval=convert_int();return "INTEGER";}
"+="		{return "ADD_ASSIGN";}
"-="		{return "SUB_ASSIGN";}
"*="		{return "MUL_ASSIGN"; }
"/="		{return "DIV_ASSIGN";}
"%="		{return "MOD_ASSIGN"; }
">>"		{return  "RIGHT_OP"; }
"<<"		{return "LEFT_OP"; }
"++"		{return "INC_OP"; }
"--"		{return "DEC_OP";}
"->"		{return "PTR_OP"; }
"&&"		{return "ADD_OP";}
"<="		{return "LE_OP";}
">="		{return "GE_OP";}
"=="		{return "EQ_OP";}
"!="		{return "NE_OP";}
"!"		{return ("!");}
"+"		{return ("+");}
"-"		{return ("-");}
"/"		{return ("/");}
"%"		{return ("%");}
"<"		{return ("<");}
">"		{return (">");}
":"		{return ("SEMICOLON");}
"?"		{return ("?");}
";"		{return (";");}
","		{return (",");}
"["		{return ("[");}
"]"		{return	("]");}
"{"		{return ("{");}
"}"		{return ("}");}
"="		{return ("=");}
(		{return ("(");}
)		{return (")");}
%%
struct TOKEN{
	string nameOrVal;
	string type;
	long address;
};

template <class Type>  
Type stringToNum(const string& str)  
{  
    istringstream iss(str);  
    Type num;  
    iss >> num;  
    return num;      
}
int convert_port(){
	return stringToNum<int>(str.substr(1,str.length()-1));
}
int convert_int(){
	return stringToNum<int>(str);
}

float convert_float(){
	return stringToNum<float>(str);
}

int install_id(){//装载IDENTIFER符号表
	
}
int main()
{
   yylex();
   return 0;
}