C++结构 & 运算符重载

被 palabos 倒逼学 C++。

结构

一个有构造函数，有成员函数的结构。返回回一个矩形格子的四个点：

#include <iostream>
using namespace std;

struct Box2D {
    Box2D() : x0(), x1(), y0(), y1() { }
    // 冒号后面对成员进行初始化
    Box2D(int x0_, int x1_, int y0_, int y1_)
        : x0(x0_), x1(x1_), y0(y0_), y1(y1_)
    { }
    /// Return same box, shifted by (deltaX,deltaY)
    Box2D shift(int deltaX, int deltaY) const {
        return Box2D(x0+deltaX, x1+deltaX, y0+deltaY, y1+deltaY);
        // 返回一个结构
    }

    bool operator==(Box2D const& rhs) const {
        return x0 == rhs.x0 && y0 == rhs.y0 &&
               x1 == rhs.x1 && y1 == rhs.y1;
    } // 运算符重载

    int x0, x1, y0, y1;
};

int main()
{
    Box2D box = {1,10,2,9};
    cout << "box: " << box.x0 << "  " << box.x1 << endl;
    Box2D box1,box2;
    cout << "box1: " << box1.x0 << "  " << box1.x1 << endl;
    box2 = box.shift(1,2);
    cout << "box2: " << box2.x0 << "  " << box2.x1 << endl;
    box1 = box2;
    cout << "box1: " << box1.x0 << "  " << box1.x1 << endl;

    if (box1 == box2)
    {
        cout << "There are equal!" << endl;
    }

    return 0;
}

运算符重载

重载运算符 == : operator == ()

bool operator==(Box2D const& rhs) const {
    return x0 == rhs.x0 && y0 == rhs.y0 &&
           x1 == rhs.x1 && y1 == rhs.y1;

box1 == box2 其实是 box1.operator(box2)。第一个对象调用方法，第二个对象作为参数。

if (box1 == box2)
{
    cout << "There are equal!" << endl;
}