词法分析器实验报告
1.实验平台：
visual studio 2010
2.实验目的
设计、编制、调试一个词法分析子程序－识别单词，加深对词法分析原理的理解。
3.数字状态转换图：
4本程序自行规定：
(1)关键字"begin","end","if","then","else","while","write","read",
"do", "call","const","char","until","procedure","repeat"
(2)运算符："+","-","*","/","="
(3)界符："{","}","[","]",";",",",".","(",")",":"
(4)其他标记 如字符串，表示以字母开头的标识符。
(5)空格、回车、换行符跳过。
5.程序源代码：
源文件主要放在三个文件中：stdafx.h主要存放头文件stdafx.cpp主要存放函数的定义Compilertest.cpp ：主函数定义
// stdafx.h : 标准系统包含文件的包含文件，
// 或是经常使用但不常更改的
// 特定于项目的包含文件
#pragma once
#include "targetver.h"
#include <stdio.h>
#include <tchar.h>
#include <iostream>
#include <fstream>
#include <string>
#include "compiler.h"
using namespace std;
int const keyLength=26; //定义关键字数组的大小
int const OPLENGTH1=8; //定义运算符数组大小
int const JLENGTH=9; //定义界符数组的大小
int const BFLENGTH=640; //定义双缓冲数组大小
//函数声明
char firstRead(); //首次读取
char getChar(); //读取一个字符
bool isLetter(char C); //判断字符串
bool isDigit(char C); //判断数字
bool isUnderLine(char C); //判断是否为下划线
bool isKeyLetter(string str); //判断关键字
bool isJieFu(char C); //判断界符
bool isOperator(char C); //判断运算符
void back(); //当前指针向前退一个
void myPrint(string s1,string s2); //自定义文件输出函数
char ciFaFenXi(char now); //词法分析函数
void readFBiao( ); //读取符号表
bool inGuanJianBiao(string fuhaobiao[2][600],string str);
bool inBainLiangBiao(string fuhaobiao[2][600],string str);
stdafx.cpp :
// stdafx.cpp : 只包括标准包含文件的源文件
// Compilertest.pch 将作为预编译头
// stdafx.obj 将包含预编译类型信息
#include "stdafx.h"
char buffer1[BFLENGTH]; //双缓冲1
char buffer2[BFLENGTH]; //双缓冲2
//定义符号表的当前大小
int fcount1=0;
int fcount2=0;
//定义关键字数组
string keyStr[keyLength]={"cout","cin","this","if","else","while","true","false","iostream","new","main","infile","std","endl",
"using","namespace","char","int","double","float","bool","return","include","public","class","void"};
//定义变量
char myOperator1[OPLENGTH1]={'>','<','+','-','*','/','=','!'}; //运算符数组
char jiefu[JLENGTH]={'{','}','(',')',':',';','.','#',','}; //界符
//定义文件读取，输出流变量
ifstream infile("G://a.txt",ios::binary);
ofstream outfile("G://b.txt",ios::binary);
char now; //储存当前字符
string token=""; //用于存放字符串
char *startP,*forwardP; //定义开始和向前指针
string fuhaobiao[2][600]; //定义一个符号表(存放标识符)
//判断C是否为字母
bool isLetter(char C){
if ((C>='a'&&C<='z')||(C>='A'&&C<='Z')){
return true;
}
else return false;
}
//判断是否为数字
bool isDigit(char C){
if(C>='0'&&C<='9'){
return true;
}else
return false;
}
//判断是否为界符
bool isJieFu(char C){
for (int i=0;i<JLENGTH;i++){
if (C==jiefu[i]){
return true;
}else
continue;
}
return false;
}
//判断是否为运算符
bool isOperator(char C){
for (int i=0;i<OPLENGTH1;i++){
if (C==myOperator1[i]){
return true;
}else
continue;
}
return false;
}
//判断是否为下划线
bool isUnderLine(char C){
if(C=='_'){
return true;
}else
return false;
}
//判断是否为系统关键字
bool isKeyLetter(string str){
for(int i=0;i<keyLength;i++){
if (str==keyStr[i]){
return true;
}
}
return false;
}
//自定义输出函数
void myPrint(string s1,string s2){
if (!outfile){
cout <<"文件打开失败"<<endl;
exit(1);
}
cout<<"< "<<s1<<" , "<<s2<<" >\r\n"<<endl;
outfile<<"< "<<s1<<" , "<<s2<<" >\r"<<endl;
}
//定义遍历符号表函数
void readFBiao( ){
for (int i=0;i<2;i++){
if (i==0){ //遍历关键字符号表
for (int j=0;j<fcount1;j++){
cout<<fuhaobiao[i][j]<<endl;
}
}
//变量符号表
if (i==1){ //遍历变量符号表
for (int j=0;j<fcount2;j++){
if (j==0){
cout<<"输出变量表中的内容！"<<endl;
}
cout<<fuhaobiao[i][j]<<endl;
}
}
}
}
//定义查看是否存在符号表中的函数
bool inGuanJianBiao(string fuhaobiao[2][600],string str){
for (int j=0;j<fcount1;j++){
if (str==fuhaobiao[0][j]){
return true;
}
}
return false;
}
bool inBainLiangBiao(string fuhaobiao[2][600],string str){
for (int j=0;j<fcount2;j++){
if (str==fuhaobiao[1][j]){
return true;
}
}
return false;
}
char firstRead(){
buffer1[BFLENGTH-1]=EOF;
buffer2[BFLENGTH-1]=EOF;
if (!infile){
cout <<"文件打开失败"<<endl;
exit(1);
}
forwardP=buffer1;//让指针指向第一个缓冲区
//把字符读入buffer1中
for(int i=0;i<BFLENGTH-2;i++){
if(infile.get(buffer1[i])){
}else{
infile.close();
buffer1[i]=EOF;
break;
}
}
now= getChar();
return now;
}
//定义词法分析函数
char ciFaFenXi(char now){
//循环获取
while(1){
while (now==' '){now=getChar(); }
if (now=='\r'){ //判断换行符
now=getChar();
if (now=='\n'){now=getChar();}
continue;
}else if(now==EOF) {return EOF ;
}else if (isLetter(now)){ //判断字符串
token+=now;
now=getChar();
while(isLetter(now)||isDigit(now)||isUnderLine(now)){
token+=now;
now=getChar();
}
if (isKeyLetter(token)){ //判断关键字类型
myPrint(token,"关键字");
if (!inGuanJianBiao( fuhaobiao,token)){
fuhaobiao[0][fcount1++]=token; ///加入符号表中
}
}else{
myPrint(token,"变量");
if (!inBainLiangBiao( fuhaobiao,token)){
fuhaobiao[1][fcount2++]=token;
}
}
token="";
return now;
}else if (isDigit(now)){ //判断整数
token+=now;
now=getChar();
while(isDigit(now)){
token+=now;
now=getChar();
}
if (now=='.'){ //判断小数
token+=now;
now=getChar();
while(isDigit(now)){
token+=now;
now=getChar();
}
myPrint(token,"小数");
token="";
return now;
}
myPrint(token,"整数");
token="";
return now;
}else if (isJieFu(now)){ //判断界符
string result;
myPrint(result.assign(1,now),"界符");
now=getChar();
return now;
}else if (isOperator(now)){ //判断运算符
token+=now;
now=getChar();
if (now=='='){
token+=now;
now=getChar();
myPrint(token,"双目运算符");
token="";
return now;
}
if(token!="!")
myPrint(token,"单目运算符");
else myPrint(token,"其他");
token="";
return now;
}else {
string result;
myPrint(result.assign(1,now),"其他");
now=getChar();
return now;
}
return now;
}
infile.close();
}
//自定义getChar（）函数，运用了双缓冲，有两个字符数组作为缓冲区
char getChar(){
char next;//定义储存下一个读入的字符
if(*forwardP==EOF){//如果到缓冲区末尾,但不知是哪个缓冲区尾
if (forwardP==buffer1+BFLENGTH-1){//如果到了buffer1的末尾
//读入buffer2
for(int i=0;i<BFLENGTH-1;i++){
if(infile.get(buffer2[i])){
}else{
infile.close();
buffer2[i]=EOF;
break;
//exit(1);
}
}
forwardP=buffer2;
getChar();
}else if (forwardP==buffer2+BFLENGTH-1){//如果到了buffer2的末尾
//读入buffer1
for(int i=0;i<BFLENGTH-1;i++){
if(infile.get(buffer1[i])){
//cout<<buffer1[i]<<"";
}else{
//cout<<endl<<"The file is end!!!!!!!!!";
infile.close();
buffer1[i]=EOF;
break;
//exit(1);
}
}
forwardP=buffer1;
getChar();
}else{
infile.close();
return EOF;
//exit(1);
}
}else{
if (*forwardP==EOF){
exit(1);
}
next=*forwardP;//把他付给next
//cout<<next;
forwardP+=1;//向下走一个
return next;
}
}
//定义后退一个函数
void back(){
if(forwardP==buffer1){//如果当前指针指向buffer1的开头
forwardP=buffer2+BFLENGTH-2;//转而指向buffer2的末尾
}else if(forwardP==buffer2){
forwardP=buffer1+BFLENGTH-2;//转而指向buffer1的末尾
}else {
forwardP-=1;
} }
Compilertest.cpp主函数：
// Compilertest.cpp : 定义控制台应用程序的入口点。
//
//@author lixingle
//词法分析器小程序
#include "stdafx.h"
using namespace std;
char nextC;
int main(){
nextC= firstRead();
//调用词法分析函数
while(nextC!=EOF)
nextC=ciFaFenXi(nextC);
//遍历符号表
cout <<"遍历符号表开始！"<<endl;
readFBiao( );
return 0;
}
4.测试结果：
