C++之运算符重载

 C++ Code 

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/*
    名称：C++运算符重载
    作者：Michael Joessy
    日期：2017-06-05
    知识：给原有的运算符赋予新的功能
    C++的一大特性就是重载(overload)，通过重载可以把功能相似的几个函数合为一个，使得程序更加简洁、高效。
    在C++中不仅函数可以重载，而且运算符也可以重载。
    运算符重载的本质：函数重载
    关键字：operator
    分类：成员函数重载   友元函数重载
*/

#include <iostream>
#include <string>
using namespace std;

// class Coordinate
class Coordinate
{
    //friend Coordinate& operator-(Coordinate& coor);
    //friend Coordinate operator+(const Coordinate& coor1, const Coordinate& coor2);
    friend ostream& operator<<(ostream& out, const Coordinate& coor);

public:
    Coordinate(int nX, int nY);
    int getX();
    int getY();
    Coordinate& operator-();
    Coordinate& operator++();   //前置++
    Coordinate operator++(int); //后置++

    Coordinate operator+(const Coordinate& coor);

    int operator[](int nIndex);
protected:
private:
    int m_nX;
    int m_nY;
};

Coordinate::Coordinate( int nX, int nY )
{
    m_nX = nX;
    m_nY = nY;
}

Coordinate& Coordinate::operator-()
{
    m_nX = -m_nX;
    m_nY = -m_nY;
    return *this;
}

Coordinate& Coordinate::operator++()
{
    m_nX++;
    m_nY++;
    return *this;
}

Coordinate Coordinate::operator++( int )
{
    Coordinate old(*this);
    m_nX++;
    m_nY++;
    return old;
}

int Coordinate::getX()
{
    return m_nX;
}

int Coordinate::getY()
{
    return m_nY;
}

Coordinate Coordinate::operator+( const Coordinate& coor )
{
    Coordinate tmp(0, 0);
    tmp.m_nX = this->m_nX + coor.m_nX;
    tmp.m_nY = this->m_nY + coor.m_nY;
    return tmp;
}

int Coordinate::operator[]( int nIndex )
{
    if (0 == nIndex)
    {
        return m_nX;
    }
    else if (1 == nIndex)
    {
        return m_nY;
    }
    else
    {
        return -1;
    }
}

//Coordinate& Coordinate::operator-( Coordinate& coor )
//{
// coor.m_nX = -coor.m_nX;
// coor.m_nY = -coor.m_nY;
// return *this;
//}

//Coordinate Coordinate::operator+( const Coordinate& coor1, const Coordinate& coor2 )
//{
// Coordinate tmp(0, 0);
// tmp.m_nX = coor1.m_nX + coor2.m_nX;
// tmp.m_nY = coor1.m_nY + coor2.m_nY;
// return tmp;
//}

ostream& operator<<(ostream& out, const Coordinate& coor)
{
    out << coor.m_nX << "," << coor.m_nY;
    return out;
}

int main(void)
{
    /************************************************************************/
    /* string  operator = + <<
    /************************************************************************/
    string str1("Michael");
    string str2("Joessy");
    string str3 = str1 + " " + str2;
    cout << str3 << endl;

    /************************************************************************/
    /* 一元运算符重载
    /************************************************************************/
    // -(负号)
    Coordinate coor1(2, 3);
    -coor1;                 //coor1.operator-();
                            //operator-(coor1);    friend
    cout << coor1.getX() << "," << coor1.getY() << endl;
    // ++(前置)
    ++coor1;                //coor1.operator++();
    cout << coor1.getX() << "," << coor1.getY() << endl;
    // ++(后置)
    coor1++;                //coor1.operator++(0);
    cout << coor1.getX() << "," << coor1.getY() << endl;

    /************************************************************************/
    /* 二元运算符重载
    /************************************************************************/
    Coordinate coorAdd1(1, 3);
    Coordinate coorAdd2(2, 5);
    Coordinate coorAddRes3(0, 0);
    coorAddRes3 = coorAdd1 + coorAdd2;   //coorAdd1.operator+(coorAdd2)
                                         //operator+(coorAdd1, coorAdd2) friend
    cout << coorAddRes3.getX() << "," << coorAddRes3.getY() << endl;

    /************************************************************************/
    /* 输出运算符重载
    /* 必须使用友元运算符重载
    /************************************************************************/
    Coordinate coorTest(7, 8);
    cout << coorTest << endl;            //operator<<(cout, coorTest)

    /************************************************************************/
    /* []索引运算符重载
    /* 必须使用成员运算符重载
    /************************************************************************/
    Coordinate coorIndex(3, 5);
    cout << coorIndex[0] << endl;        //coorIndex.operator[](0)
    cout << coorIndex[1] << endl;        //coorIndex.operator[](1)

    cin.get();
    return 0;
}