实验1

#include<iostream>
using std::cout;
using std::endl;

class Point
{
    public:
        Point(int x0=0, int y0=0);
        Point(const Point&p);
        ~Point()=default;
        
        int get_x() const { return x; }
        int get_y() const { return y; }
        void show() const;
    
    private:
        int x,y;
};

Point::Point(int x0, int y0): x{x0},y{y0}
{
    cout << "copy constructor called." << endl;
}

Point::Point(const Point& p): x{p.x}, y{p.y} 
{
    cout << "copy constructor called." << endl;
}

void Point::show() const
{
    cout<<"("<< x <<","<< y <<")"<<endl;
}

int main()
{
    Point p1(3,9);
    p1.show();
    
    Point p2=p1;

    p2.show();
    
    Point p3(p2);
    p1.show();
    
    cout<< p3.get_x() <<endl;
}

#include <iostream>
class X{
public:
 X(); 
 ~X(); 
 X(int m); 
 X(const X& obj); 
 X(X&& obj) noexcept; 
 void show() const; 
private:
 int data;
};
X::X(): data{42} {
 std::cout << "default constructor called.\n"; 
}
X::~X() {
 std::cout << "destructor called.\n"; 
}
X::X(int m): data{m} {
 std::cout << "constructor called.\n";
}
X::X(const X& obj): data{obj.data} {
 std::cout << "copy constructor called.\n";
}
X::X(X&& obj) noexcept: data{obj.data} {
 std::cout << "move constructor called.\n"; 
}
void X::show() const {
std::cout << data << std::endl;
}
int main() {
X x1; 
 x1.show();
 X x2{2049};
 x2.show(); 
 X x3{x1}; 
 x3.show();
 X x4{ std::move(x2) }; 
 x4.show();
}

X x1; 执行时默认构造函数被调用；

X x2{2049}; 执行时构造函数被调用；
X x3{x1}; 执行时复制构造函数被调用；

X x4{ std::move(x2) }; 执行时移动构造函数被调用；

每个对象在使用完后都会调用一次析构函数；

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

class Rectangle{
public:
    Rectangle():length(2.0),width(1.0){    };
    Rectangle(double l,double w):length(l),width(w){ };
    Rectangle(const Rectangle &rec):length(rec.length),width(rec.width){ };
    ~Rectangle()=default;
    
    double len() const {return length;}
    double wide() const {return width;}
    double area() const {return length*width;}
    double circumference() const {return 2*(length+width);}
    
    void resize(double times){
        length*=times;
        width*=times;
    }
    
    void resize(double l_times,double w_times){
        length*=l_times;
        width*=w_times;
    }
        
private:
    double length;
    double width;
        
};

void output(const Rectangle &rect) { 
    cout << "矩形信息: \n"; 
    cout << fixed << setprecision(2);
    cout<<"长:"<<"\t"<<rect.len()<<endl; 
    cout<<"宽:"<<"\t"<<rect.wide()<<endl; 
    cout<<"面积:"<<"\t"<<rect.area()<<endl; 
    cout<<"周长:"<<"\t"<<rect.circumference()<<endl; 
    cout<<endl;
}

int main() {
    Rectangle rect1; 
    output(rect1);
    
    Rectangle rect2(10, 5);
    output(rect2);
    
    Rectangle rect3(rect1);
    rect3.resize(2);
    output(rect3);
    
    rect3.resize(5, 2);
    output(rect3);
}