作业.cpp

词法分析器

#include <iostream>
#include <cstdio>
#include <fstream>
#include <string>
#include <vector>
#include <cstdlib>
#include <iomanip>
#include <bitset>
using namespace std;
string strToken;
vector<string> *words=new vector<string>;
static const string table[5]={"DIM","IF","DO","STOP","END"};
vector<string> tableID;
vector<string> tableConst;
char ch;
int code,value;
inline bool IsLetter()
{
    if(ch>='A'&&ch<='Z'||ch>='a'&&ch<='z')
        return true;
    else
        return false;
}
inline bool IsDigit()
{
    if(ch>='0'&&ch<='9')
        return true;
    else
        return false;
}

inline void Concat()
{
    strToken.insert(strToken.end(),ch);
}

inline int Reserve()
{
    int count=1,i;
    for(i=0;i<5;i++,count++)
        if(strToken==table[i]) 
            return count;
    return 0;
}
inline int InsertId()
{	static int count=0;
    tableID.insert(tableID.end(),strToken);
	count++;
	return count; 
}
inline int InsertConst()
{   
    static int count=0;
	tableConst.insert(tableConst.end(),strToken);
	count++;
	return count;
}

int main(void)
{
    
    ifstream myFile("text1.txt");
    if(!myFile){
        cerr<<"oops!unable to open file--bailing out!\n";
            exit(-1);
    }
	strToken="";
	while(myFile>>ch){
		strToken="";
		if(IsLetter()){
	        do{
				Concat();
				myFile.get(ch);
			}while(IsLetter()||IsDigit());
			myFile.seekg(-1,ios::cur);
			
			code=Reserve();
			if(code==0){
				value=InsertId();
				cout<<strToken<<":<$ID,"<<strToken<<">"<<endl;
				continue ;
			}else{
				cout<<strToken<<":<$"<<strToken<<",->"<<endl;
				continue ;
			}
		
		}
    
		if(IsDigit()){
			do{
				Concat();
			    myFile.get(ch);
			}while(IsDigit());
			myFile.seekg(-1,ios::cur);
			value=InsertConst();
			int temp1=atoi(strToken.c_str());
			bitset<32>   myset(temp1);
			cout<<strToken<<":<$INT,"<<myset<<">"<<endl;
			continue ;
		}
    
		if(ch=='=') {
			cout<<ch<<":<$ASSIGN,->"<<endl;
			continue ;
        }
    
		if(ch=='+') {
			cout<<ch<<":<$PLUS,->"<<endl;
			continue ;
        }
    
		if(ch=='*'){
			myFile.get(ch);
			if(ch=='*'){
				cout<<ch<<ch<<":<$POWER,->"<<endl;
				continue ;
			}else{
				cout<<'*'<<":<$STAR,->"<<endl;
				myFile.seekg(-1,ios::cur);
				continue ;
			}
		}
    
		if(ch==';') {
			cout<<ch<<":<$SEMICOLON,->"<<endl;
			continue ;
        }
    
		if(ch=='(') {
			cout<<ch<<":<$LPAR,->"<<endl;
            continue ;
        }
    
	    if(ch==')') {
			cout<<ch<<":<$RPAR,->"<<endl;
            continue ;
        }
    
		if(ch=='{') {
            cout<<ch<<":<$LBRACE,->"<<endl;
            continue ;
        }
    
		if(ch=='}'){
			cout<<ch<<":<$RBRACE,->"<<endl;
			continue ;
		}
		else
			cout<<ch<<" can't be recognized!"<<endl;
    }
	system("pause");
	return 0;
}