C++ 操作符重载

通过重载操作符 << 来实现 运算符重载中的打印分数的功能。  <<将数据插入流中，即插入器

#include <iostream>
#include <string>
#include <stdlib.h>
class Rational
{
public:
    Rational(int num, int denom);//num 分子，denom 分母
    Rational operator+(Rational rhs);//rhs == right hand side
    Rational operator-(Rational rhs);
    Rational operator*(Rational rhs);
    Rational operator/(Rational rhs);

    void print();
private:
    void normalize(); //负责对分数的简化处理

    int numerator; //分子
    int denominator; //分母

    friend std::ostream& operator<<(std::ostream& os,Rational f);
    //第一个参数os 是将要向它写数据的那个流， 以‘引用传递&’方式传递的。
    //第二个参数 是打算写到那个流里的数据值，不同的operator <<() 重载函数就是因为这个输入参数才相互区别的
    //返回类型时ostream流的引用。一般说，调用oper<<()重载函数时传递给它的是哪一个流，他返回的就应该是那个流的一个引用。
};

Rational::Rational(int num, int denom)
{
    numerator = num;
    denominator = denom;

    normalize();
}

void Rational::normalize()
{
    if (denominator < 0)
    {
        numerator = -numerator;
        denominator = -denominator;
    }
    //欧里几德算法,分子分母除以最大公约数化简。
    int a = abs(numerator);
    int b = abs(denominator);

    while (b>0)
    {
        int t = a%b;
        a = b;
        b = t;
    }
    numerator /= a;
    denominator /= a;
}

Rational Rational::operator+(Rational rhs)
{
    int a = numerator;
    int b = denominator;
    int c = rhs.numerator;
    int d = rhs.denominator;

    int e = a*b + c*d;
    int f = b*d;

    return Rational(e,f);
}

Rational Rational::operator-(Rational rhs)
{
    rhs.numerator = -rhs.numerator;
    return operator+(rhs);
}

Rational Rational::operator*(Rational rhs)
{
    int a = numerator;
    int b = denominator;
    int c = rhs.numerator;
    int d = rhs.denominator;   

    int e = a*c;
    int f = b*d;

    return Rational(e,f);
}

Rational Rational::operator/(Rational rhs)
{
    int t = rhs.numerator;
    rhs.numerator = rhs.denominator;
    rhs.denominator = t;

    return operator*(rhs);
}

void Rational::print()
{
    if(numerator%denominator == 0)
        std::cout << numerator / denominator;
    else
        std::cout << numerator << "/" << denominator;
}

std::ostream& operator<<(std::ostream& os,Rational f);
int main()
{
    Rational f1(2,16);
    Rational f2(7,8);

    std::cout<< f1 << " + " << f2 << " == " << (f1 + f2) <<"\n";  //调用<<时，如果后面为rational格式，则执行重载后的<<
    std::cout<< f1 << " - " << f2 << " == " << (f1 - f2) <<"\n";
    std::cout<< f1 << " * " << f2 << " == " << (f1 * f2) <<"\n";
    std::cout<< f1 << " / " << f2 << " == " << (f1 / f2) <<"\n";
}

std::ostream& operator<<(std::ostream& os,Rational f)
{
    os<<f.numerator <<"/" << f.denominator;
    return os;
}