C++的运算符重载

一元运算符重载

---

以++为例：

#include <iostream>#include <string>using namespace std;class Stu{    friend Stu& operator++();//前置++的友元函数重载    friend Stu operator++(Stu &stu, int);//后置++的友元函数重载public:    Stu(int x, int y)    {        m_x = x;        m_y = y;    }    //后置++的成员函数重载    //Stu operator++(int)    //{    //  Stu old(*this);    //  m_x++;    //  m_y++;    //  return old;    //}    //前置++的成员函数重载    /*Stu& operator++()    {        m_x = m_x+1;        m_y = m_y+1;        return *this;    }*/    void print()    {        cout << m_x << " " << m_y<<endl;    }    int getX()    {        return m_x;    }    int getY()    {        return m_y;    }private:    int m_x;    int m_y;};////Stu& operator++(Stu &stu)//{//  stu.m_x = stu.m_x + 1;//  stu.m_y =stu.m_y + 1;//  return stu;//}/*Stu operator++(Stu &stu, int)//必须使用引用{    Stu old(stu);    stu.m_x++;    stu.m_y++;    return old;}*/int main(){    Stu stu(2,6);    //cout << (stu++).getX() << endl;    //cout << (stu++).getX() << endl;    return 0;}

---

二元运算符的重载

---

“+”的成员函数和友元函数的运算符重载

#include <iostream>#include <string>using namespace std;class Stu{    friend Stu& operator+(Stu &a, Stu &b);public:    /*Stu &operator+(Stu &stu)    {        Stu stu0(0,0);        stu0.m_x = this->m_x + stu.m_x;        stu0.m_y = this->m_y + stu.m_y;        return stu0;    }*/    Stu(int x, int y)    {        m_x = x;        m_y = y;    }    void print()    {        cout << m_x << " " << m_y<<endl;    }    int getX()    {        return m_x;    }    int getY()    {        return m_y;    }private:    int m_x;    int m_y;};Stu& operator+(Stu &a, Stu &b){       Stu c(0, 0);    c.m_x = a.m_x + b.m_x;    c.m_y = a.m_y + b.m_y;    return c;}int main(){    Stu stu1(2,6);    Stu stu2(6,2);    Stu stu0 = stu1 + stu2;    cout << stu0.getX() << " " << stu0.getY() << endl;    return 0;}

---

“<<”的运算符重载

注意：”<<”只能在友元函数中进行运算符重载，因为重载时的第一个参数必须是”ostream”类型的值。

#include <iostream>using namespace std;class Stu{    friend ostream& operator<<(ostream &out, Stu &stu);public:    Stu(int x, int y)    {        m_x = x;        m_y = y;    }    void print()    {        cout << m_x << " " << m_y<<endl;    }    int getX()    {        return m_x;    }    int getY()    {        return m_y;    }private:    int m_x;    int m_y;};ostream& operator<<(ostream &out, Stu &stu) {    out << stu.m_x << " " << stu.m_y << endl;    return out;}int main(){    Stu stu(2,6);    cout << stu << endl;    return 0;}

---

索引”[ ]”的运算符重载

注意：索引运算符只能进行成员函数的运算符重载。

#include <iostream>using namespace std;class Stu{public:    int operator[](int index)    {           if (index == 0)        {            return m_x;        }        else if (index == 1)        {            return m_y;        }    }    Stu(int x, int y)    {        m_x = x;        m_y = y;    }    void print()    {        cout << m_x << " " << m_y<<endl;    }    int getX()    {        return m_x;    }    int getY()    {        return m_y;    }private:    int m_x;    int m_y;};int main(){    Stu stu(2,6);    cout << stu[0] << endl;    cout << stu[1] << endl;    return 0;}