C++ - 用类表示分数、四则运算、以及输入输出

#include
#include
using namespace std;
void reduce(int &, int &);//¼ò»¯·ÖÊý£¬Ê¹·Ö×Ó·Öĸͬ³ýÒÔ×î´ó¹«Ô¼Êý
int gcd(int , int );//Çó×î´ó¹«Ô¼Êý 
class Fraction{ //·ÖÊýÀà 
		int up, down;
	public:
		Fraction(int u, int d){//¹¹Ô캯Êý£¬Ïȼò»¯ºóÔÙ¸³Öµ 
			reduce(u, d);
			up = u; down = d;
		}
		Fraction(){up = 0; down = 1;reduce(up, down);}//ĬÈϹ¹Ô캯Êý£¬Ä¬ÈÏΪ0£¬Áî·ÖĸΪ1£¬·ÖĸΪ1ÊÓΪÕûÊý 
		friend Fraction operator +(Fraction , Fraction); //ÉùÃ÷ÓÑÔªº¯Êý£¬²¢ÉùÃ÷ËÄÔòÔËËã 
		friend Fraction operator -(Fraction, Fraction);
		friend Fraction operator *(Fraction, Fraction);
		friend Fraction operator /(Fraction, Fraction);
		friend ostream & operator <<(ostream &, Fraction );//ÖØÔزÙ×÷·û£¬Ê¹µÃ·½±ãÊäÈëÊä³ö£¬Í¬Ê±ÔÚÊäÈëʱ½øÐмò»¯ 
		friend istream & operator >> (istream &, Fraction &);//×¢Ò⣬ÊäÈëʱÐè¶ÔFraction ÐβÎÒýÓà 
		friend void reduce(int &, int &);//ÓÉÓÚreduce»á·ÃÎÊ˽ÓÐÊý¾Ý³ÉÔ±£¬ÐèÉùÃ÷ΪÓÑÔª 
};
void reduce(int & up, int & down){ //ÓÃÓÚ¼ò»¯·ÖÊý 
	if(down < 0){ //Áî·ÖĸʼÖÕΪÕý£¬·Ö×Ó´øÕý¸ººÅ 
		up = - up;
		down = -down;
	}
	if(up ==0) down = 1; //µ±·Ö×ÓΪÁãʱ£¬·ÖĸÁîΪ1£¬²¢µ±·ÖĸΪ1ʱ£¬ÊÓΪÕûÊý¡£ 
	else{ //Çó³ö×î´ó¹«Ô¼Êý£¬²¢Ê¹·Ö×Ó·Öĸͬ³ý 
		int g = gcd(abs(up), abs(down));
		up /= g;
		down /= g;
	}
}
int gcd(int a, int b){//×¢Ò⣬Ҫʹ a¡¢b¾ùΪÕýÊý 
	return !b? a : gcd(b, a%b);
}
Fraction operator +(Fraction a, Fraction b){
	return Fraction(a.up * b.down + b.up * a.down, a.down * b.down);
}
Fraction operator -(Fraction a, Fraction b){
	return Fraction(a.up * b.down - b.up * a.down, a.down * b.down);
}
Fraction operator *(Fraction a, Fraction b){
	return Fraction(a.up * b.up, a.down * b.down);
}
Fraction operator /(Fraction a, Fraction b){
	return Fraction(a.up * b.down, a.down * b.up);
}
ostream & operator <<(ostream & output, Fraction a){
	if(a.down == 0) return output <<"INF"< a.down) return output << a.up/a.down << " " <<	abs(a.up) % a.down << "/" << a.down<> (istream & input, Fraction& a){//ÖØÔزÙ×÷·û£¬ÊäÈëʱ½øÐмò»¯ 
	input >> a.up >>a.down;
	reduce(a.up, a.down);//¼ò»¯ 
	return input;
}
int main(){
	Fraction a,b;
	cin >> a >> b;
	cout << a << b;
	cout << a + b << a - b << a * b << a / b;
	return 0;
}