C++比较运算符重载详解

class Point {
public:
    int x, y;
    Point(int x = 0, int y = 0) : x(x), y(y) {}

    // 成员函数重载 == 
    bool operator==(const Point& other) const {
        return x == other.x && y == other.y;
    }

    // 成员函数重载 !=
    bool operator!=(const Point& other) const {
        return !(*this == other);
    }
};

bool operator<(const Point& other) const {
    if (x != other.x)
        return x < other.x;
    return y < other.y;  // 按字典序比较
}

bool operator>(const Point& other) const {
    return other < *this;
}

bool operator<=(const Point& other) const {
    return !(*this > other);
}

bool operator>=(const Point& other) const {
    return !(*this < other);
}

class Point {
    // ...
public:
    Point(int x = 0, int y = 0) : x(x), y(y) {}
    // 声明为友元以便访问私有成员（如果x,y是private）
    friend bool operator==(const Point& a, const Point& b);
    friend bool operator<(const Point& a, const Point& b);
};

// 非成员函数定义
bool operator==(const Point& a, const Point& b) {
    return a.x == b.x && a.y == b.y;
}

bool operator<(const Point& a, const Point& b) {
    return std::tie(a.x, a.y) < std::tie(b.x, b.y); // 使用tie简化比较
}