c++ 简单的词法分析

scanner.h

#include<iostream>
#include<fstream>
#include<string>
using namespace std;

class Scanner{
	private:
		string infile; 
		string outfile; 
		string key[33];
		string helpkey[33];
	public:
		Scanner(string infile_temp,string outfile_temp);
		void readFile();
		void getToken(string s,ofstream &out);
		bool isLetter(char ch);
		bool isDigit(char ch);
		int reserve(const string& s);



};

　　scanner.cpp

#include "scanner.h"

using namespace std;

Scanner::        Scanner(string infile_temp,string outfile_temp){
    infile = infile_temp;
    outfile = outfile_temp;
    string key_temp[33] = {"","auto","double","int","struct","break","else","long","switch",
            "case", "enum","register","typedef","char","extern","return","union","const",
            "float","short","unsigned","continue","for","signed","void","default","goto",
            "sizeof","volatile","do","if","while","static"};

    for(int i=0;i<33;i++){
        key[i] = key_temp[i];
    }        
        
    }


void Scanner::readFile(){
    
    ifstream in(infile);
    ofstream out(outfile);
    string s;

    while(getline(in,s)){
        getToken(s,out);
    }


}

//判断是否letter
bool Scanner::isLetter(char ch){
    if((ch>=65&&ch<=90)||(ch>=97&&ch<=122)||ch==35||ch==46)
    return true;
    else 
    return false;

}


//判断是否数字
bool Scanner::isDigit(char ch){
    if(ch>=48&&ch<=57)
    return true;
    else 
    return false;
}

//查找关键字
int Scanner::reserve(const string& s){
    for(int i=1;i<33;i++)
    if(s==key[i])
       return i;
    return 0;

}



void Scanner::getToken(string s,ofstream &out){

            size_t i=0,code;
            char ch;
            string temp="";
            ch=s[i];
            while(i<s.length()){

            //如果是空跳过
            while(i<s.length()&&ch==' '){
               i++;
               ch=s[i];
            }
            //是字母
            if(isLetter(ch)){
                while((isLetter(ch)||isDigit(ch))&&i<s.length()){
                   temp+=ch;
                   i++;
                   ch=s[i];
                }
                i--;
                code=reserve(temp);
                    if(code==0){
                       out<<temp<<'\t'<<"标识符"<<endl;
                       temp="";
                    }else{ 
                       out<<temp<<'\t'<<"关键字"<<endl;
                          temp="";
                    }

            }else if(isDigit(ch)){
                while(isDigit(ch)){
                   temp+=ch;
                   i++;
                   ch=s[i];
                }
                i--;
                out<<temp<<'\t'<<"常数"<<endl;
                temp="";
            }else if(ch=='='){
                i++;
                ch=s[i];
                if(ch== '=' )
                   out<<"=="<<'\t'<<"判断相等"<<endl;
                else{
                   i--;
                      out<<"="<<'\t'<<"赋值"<<endl;
                } 

            }
            else if(ch=='+'){
               i++;
                  ch=s[i];
               if(ch=='+')
               out<<"++"<<'\t'<<"加1"<<endl;
               else{
                i--;
                out<<"+"<<'\t'<<"加号"<<endl;
               }
            }
            else if(ch=='&'){
               i++;
                  ch=s[i];
               if(ch=='&')
               out<<"&&"<<'\t'<<"与"<<endl;
               else{
                i--;
                out<<"&"<<'\t'<<"按位与"<<endl;
               }
            }
            else if(ch=='|'){
               i++;
                  ch=s[i];
               if(ch=='|')
               out<<"||"<<'\t'<<"或"<<endl;
               else{
                i--;
                out<<"|"<<'\t'<<"按位或"<<endl;
               }
            }

            else if(ch=='-')
            out<<ch<<'\t'<<"减号"<<endl;
            else if(ch==';')
            out<<ch<<'\t'<<"分号"<<endl;
            else if(ch=='(')
            out<<ch<<'\t'<<"左括号"<<endl;
            else if(ch==')')
            out<<ch<<'\t'<<"右括号"<<endl;
            else if(ch=='{')
            out<<ch<<'\t'<<"左花括号"<<endl;
            else if(ch=='}')
            out<<ch<<'\t'<<"右花括号"<<endl;
            else if(ch=='*'){
            i++;
            ch=s[i];
            if(ch=='*')
               out<<"**"<<'\t'<<"运算符"<<endl;
            else{
               i--;
                  out<<"*"<<'\t'<<"乘号"<<endl;
            }


            }
            else if(ch=='<'){
            i++;
            ch=s[i];
            if(ch=='=')
               out<<"<="<<'\t'<<"小于等于"<<endl;
            else{
               i--;
                  out<<"<"<<'\t'<<"小于"<<endl;
            } 

            }
               else if(ch=='>'){
            i++;
            ch=s[i];
            if(ch=='=')
               out<<">="<<'\t'<<"大于"<<endl;
            else{
               i--;
                  out<<">"<<'\t'<<"小于"<<endl;
            }


            }
            else
            return ;
            i++;
            ch=s[i];
            }

}