C++几个运算符重载示例

运算符重载为非成员函数和成员函数对比：

#include 
using namespace std;

class Complex
{
public:
    Complex(double r = 0, double i = 0) { real = r; image = i;}

public:
    // 非成员函数，用friend作用是友元函数可以用类中的任何数据
    friend Complex operator-(Complex c1, Complex c2);
    // 成员函数
    Complex operator+(Complex c1);
    
    void show() { cout << real << "+" << image << "i" << endl; }

private:
    double real = 0.0;
    double image = 0.0;
};

Complex Complex::operator+(Complex 1)
{
    return Complex(real + c1.real, image + c1.image);
}

Complex operaotr-(Complex c1, Complex c2)
{
    return Complex(c1.real - c2.real, c1.image - c2.image);
}

int main()
{
    Complex c3, c1(3, 4), c2(1, 2);
    c2 = c1 - c2;   // 即 c3 = operator-(c1, c2)
    c2.show();
    c3 = c1 + c2;   // 即 c3 = c1.operaotr+(c2)
    c3.show();

    return 0;
}

重载++ –

Complex operator ++();  // 前置++运算符
Complex operator ++(int);   // 后置++运算符

Complex& Complex::operator++()  // 这里用引用，可以减少一次复制操作
{
    ++real;
    return *this;
}

Complex Complex::operator(int)
{
    return Complex(real++, image);
}

重载 >> 和 << 运算符

class Circle
{
public:
    friend istream& operator >>(istream &i, Circle &m);  // 非成员函数 
    friend ostream& operator <<(ostream &o, Circle &m);  // 非成员函数

private:
    double raidus;
};

istream& operator >>(istream& i, Circle &m)
{
    cin >> m.radius;
    return i;
}

ostream& operator <<(ostream &o, Circle &m)
{
    cout << m.radius;
    return o;
};