词法分析器C++实现

字符集类，头文件，若不需要去掉红字
#ifndef _WORDMAP_H
#define _WORDMAP_H

#include

class word{
public:
int ID;
string content;
word (){ID = 0; }
void set(intid,string con){
ID = id;
content =con;
}
friendostream& operator<<(ostream&out,word temp);
};
//简单的重载流操作运算符
ostream& operator<<(ostream&out,word temp){
out<<'('<return out;

}

//识别类用于读写字符
class Recognize{
private:
intmapsize;
map MyMap;//字符集地图
int model;//处在第几处理模式
char TempCan;//作为读入字符的缓冲区
public:
Recognize(){
model=0;
TempCan=' ';
freshmap();
}
voidfreshmap();
word read(istream& input );
int Model(char ch);
};

void Recognize::freshmap()//初始化 map中的变量对应
{
MyMap["for"]=1;
MyMap["if"]=2;
MyMap["then"]=3;
MyMap["else"]=4;
MyMap["while"]=5;
MyMap["+"]=6;
MyMap["-"]=7;
MyMap["*"]=8;
MyMap["/"]=9;
MyMap["="]=10;
MyMap[">"]=11;
MyMap["<"]=12;
MyMap["("]=13;
MyMap[")"]=14;
MyMap[";"]=15;
MyMap["num"]=16;
MyMap["#"]=0;
mapsize=16;
}

word Recognize::read( istream& input )//读字符函数从流中
{
word New;
string s;
model = 0;
while(' '==TempCan||'\n'==TempCan) input.get(TempCan);
model=Model(TempCan);

//读一个单元，然后直接拿去匹配结果直接写入 new
switch(model){
case 1://数字处理
s=s+TempCan;
input.get(TempCan);
while (1==Model(TempCan))
{
s=s+TempCan;
input.get(TempCan);
}
break;
case 2://关键字或者变量
s=s+TempCan;
input.get(TempCan);
while (2==Model(TempCan))
{
s=s+TempCan;
input.get(TempCan);
}
break;
case 3://处理操作符
s=s+TempCan;
input.get(TempCan);
break;
case 5://结束
s=s+TempCan;
break;
}
pair mm(s, mapsize+1);
if (model==1)
{
New.set(16,s);
}
else if (MyMap.insert(mm).second)
{
mapsize++;
New.set(MyMap[s],s);
}
elseNew.set(MyMap[s],s);
return New;

}
int Recognize::Model( char ch )//模式判断函数从缓冲中看目前处于第几读取模式
{
int n;
switch (ch)
{
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
n = 1;//说明接下来处理的是数字
break;
case '+':
case '-':
case '*':
case '=':
case '<':
case '>':
case ';':
case '(':
case ')':
n = 3;//处理操作符
break;
case '#':
n = 5;//文件结束
break;
default:
n = 2;//处理变量或关键字
//case '\n':
//case ' ':
// model = 3;
// break;
//case '#':
}
return n;
}
#endif

Main函数
#include
#include
#include "WordMap.h"
using namespace std;
void main(){
Recognize test;
word p;
p=test.read(cin);
while(p.ID){
cout<p=test.read(cin);
}
}