解释ostream& operator<<(ostream& out, Point& p) { out << p.m_X << " " << p.m_Y ; return out; }

这是一个重载了输出运算符 "<<" 的函数，它接受一个输出流对象和一个 Point 类型的对象作为参数。在函数内部，我们通过输出流对象 out 将 Point 对象的成员变量 m_X 和 m_Y 输出到控制台，并在两个值之间加入了一个空格。最后，我们将输出流对象 out 返回，以便能够进行链式输出。这样，我们就可以直接使用 cout 对象输出 Point 对象了，例如：

Point p(1, 2);
cout << p << endl; // 输出结果为：1 2

相关问题

#include <iostream> #include <string> using namespace std; class Point { public: string name; double x; double y; friend ostream& operator<<(ostream& os, const Point& p); }; ostream& operator<<(ostream& os, const Point& p) { os << p.name << "(" << p.x << "," << p.y << ")"; return os; } int main() { Point pt={2,3}; cout << pt << endl; return 0; }如何绘制点与点之间的相对位置

在这个程序中，我们定义了一个表示二维点的类 Point，其中包含了点的名称和 x,y 坐标。我们还重载了输出运算符 <<，使得可以方便地输出 Point 对象。

如果想要绘制点与点之间的相对位置，需要使用图形库或者绘图软件。以下是使用 Qt 图形库绘制的示例代码：

#include <QtGui>

class Point {
public:
    QString name;
    double x;
    double y;
};

class MyWidget : public QWidget {
public:
    MyWidget(QWidget *parent = nullptr) : QWidget(parent) {
        setFixedSize(400, 400);
    }

    void paintEvent(QPaintEvent *event) override {
        Q_UNUSED(event);

        QPainter painter(this);
        painter.setRenderHint(QPainter::Antialiasing);

        // 设置点的坐标
        Point p1 = {"A", 100, 100};
        Point p2 = {"B", 200, 200};
        Point p3 = {"C", 300, 100};

        // 绘制点
        painter.setPen(Qt::black);
        painter.drawEllipse(p1.x - 3, p1.y - 3, 6, 6);
        painter.drawEllipse(p2.x - 3, p2.y - 3, 6, 6);
        painter.drawEllipse(p3.x - 3, p3.y - 3, 6, 6);

        // 绘制点之间的相对位置
        painter.setPen(Qt::red);
        painter.drawLine(p1.x, p1.y, p2.x, p2.y);
        painter.drawLine(p2.x, p2.y, p3.x, p3.y);
        painter.drawLine(p3.x, p3.y, p1.x, p1.y);
    }
};

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);

    MyWidget widget;
    widget.show();

    return app.exec();
}

在上述代码中，我们定义了一个继承自 QWidget 的 MyWidget 类，并重载了它的 paintEvent 函数，在此函数中使用 QPainter 绘制出点和线段。通过设置 QPen 的颜色和线宽，可以实现不同的效果。

#include <iostream>using namespace std;const double PI = 3.14159265358979323846;class Point {public: Point(double xx = 0, double yy = 0) : x(xx), y(yy) {} friend istream& operator>>(istream& is, Point& p); friend ostream& operator<<(ostream& os, const Point& p);protected: double x, y;};istream& operator>>(istream& is, Point& p) { is >> p.x >> p.y; return is;}ostream& operator<<(ostream& os, const Point& p) { os << "(" << p.x << ", " << p.y << ")"; return os;}class Circle : public Point {public: Circle(double xx = 0, double yy = 0, double rr = 0) : Point(xx, yy), r(rr) {} double area() const { return PI * r * r; } friend istream& operator>>(istream& is, Circle& c); friend ostream& operator<<(ostream& os, const Circle& c);protected: double r;};istream& operator>>(istream& is, Circle& c) { is >> static_cast<Point&>(c) >> c.r; return is;}ostream& operator<<(ostream& os, const Circle& c) { os << "Center: " << static_cast<const Point&>(c) << ", Radius: " << c.r; return os;}class Cylinder : public Circle {public: Cylinder(double xx = 0, double yy = 0, double rr = 0, double hh = 0) : Circle(xx, yy, rr), h(hh) {} double volume() const { return Circle::area() * h; } friend istream& operator>>(istream& is, Cylinder& cy); friend ostream& operator<<(ostream& os, const Cylinder& cy);protected: double h;};istream& operator>>(istream& is, Cylinder& cy) { is >> static_cast<Circle&>(cy) >> cy.h; return is;}ostream& operator<<(ostream& os, const Cylinder& cy) { os << "Base: " << static_cast<const Circle&>(cy) << ", Height: " << cy.h; return os;}int main() { Circle c(0, 0, 1); cout << "Input circle info: "; cin >> c; cout << c << endl; cout << "Circle area: " << c.area() << endl; Cylinder cy(0, 0, 1, 2); cout << "Input cylinder info: "; cin >> cy; cout << cy << endl; cout << "Cylinder volume: " << cy.volume() << endl; return 0;}输出结果是

Input circle info: 1 2
Center: (1, 2), Radius: 1
Circle area: 3.14159
Input cylinder info: 1 2 3
Base: Center: (1, 2), Radius: 3.14159, Radius: 3
, Height: 3
Cylinder volume: 28.2743