C++运算符重载

运算符重载（操作符重载）：可以为运算符增加一些新的功能。

class Point
{
    friend Point operator+(const Point &, const Point &);
private:
    int x, y;
public:
    int get_x() { return this->x; }
    int get_y() { return this->y; }
    Point(int x, int y) : x(x), y(y) {  }
    void display()
    {
        printf("(%d, %d)\n", this->x, this->y);
    }
};

Point operator+(const Point &p1, const Point &p2)
{
    return Point(p1.x + p2.x, p1.y + p2.y);
}

int main()
{
    Point p1(1, 2);
    Point p2(3, 4);
    Point p3 = p1 + p2;
    // 相当于
    // Point p3 = operator+(p1, p2);
    p3.display();
    return 0;
}

写成成员函数

也可以写成成员函数

class Point
{
private:
    int x, y;
public:
    Point(int x, int y) : x(x), y(y) {  }
    void display()
    {
        printf("(%d, %d)\n", this->x, this->y);
    }

    Point operator+(const Point &p)
    {
        return Point(this->x + p.x, this->y + p.y);
    }

};

int main()
{
    Point p1(1, 2);
    Point p2(1, 2);
    Point p3 = p1 + p2;
    // 相当于
    // Point p3 = p1.operator+(p2);
    p3.display();
    return 0;
}

更多运算符重载

class Point
{
    friend ostream &operator<<(ostream &, const Point &);
    friend istream &operator>>(istream &, Point &);
private:
    int x, y;
public:
    Point(int x = 0, int y = 0) : x(x), y(y) {  }
    void display()
    {
        printf("(%d, %d)\n", this->x, this->y);
    }

    const Point operator+(const Point &p) const
    {
        return Point(this->x + p.x, this->y + p.y);
    }

    const Point operator-(const Point &p) const
    {
        return Point(this->x - p.x, this->y - p.y);
    }

    Point &operator+=(const Point &p)
    {
        this->x += p.x, this->y += p.y;
        return *this;
    }

    bool operator==(const Point &p) const
    {
        return this->x == p.x && this->y == p.y;
    }

    bool operator!=(const Point &p) const
    {
        return this->x != p.x || this->y != p.y;
    }

    const Point operator-() const
    {
        return Point(-this->x, -this->y);
    }

    // 前置++
    Point &operator++()
    {
        this->x++, this->y++;
        return *this;
    }

    // 后置++
    const Point operator++(int)
    {
        Point t(this->x, this->y);
        this->x++, this->y++;
        return t;
    }
};

ostream &operator<<(ostream &cout, const Point &p)
{
    return cout << "(" << p.x << "," << p.y << ")";
}

istream &operator>>(istream &cin, Point &p)
{
    return cin >> p.x >> p.y;
}