实验一

task2:

#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 << "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(4, 5);
    p1.show();
    
    Point p2 = p1;
    p2.show();
    
    Point p3{p2};
    p3.show();
    cout << p3.get_x() << endl;
}

 运行结果：                        修改代码：                  修改后结果：
  

task3:

#include <iostream>
#include <iomanip>

using std::cout;
using std::endl;

class Clock 
{
    public:
        Clock(int h = 0, int m = 0, int s = 0);
        Clock(const Clock& t);
        ~Clock() = default;
        
        void set_time(int h, int m = 0, int s = 0);
        void show_time() const;
    private:
        int hour, minute, second;
};

Clock::Clock(int h, int m, int s): hour{h}, minute{m}, second{s} 
{
    cout << "constructor called" << endl;
}

Clock::Clock(const Clock& t): hour{t.hour}, minute{t.minute},second{t.second} 
{
    cout << "copy constructor called" << endl;
}

void Clock::set_time(int h, int m, int s) 
{
    hour = h;
    minute = m;
    second = s;
}

void Clock::show_time() const 
{
    using std::setw;
    using std::setfill;
    cout << setfill('0') << setw(2) << hour << ":"<< setw(2) << minute << ":"<< setw(2) << second << endl;
}

Clock reset() 
{
    return Clock(0, 0, 0);

}

int main()
{
    Clock c1(12, 0, 5);
    c1.show_time();
    
    c1 = reset();
    c1.show_time();
    
    Clock c2(c1);
    c2.set_time(6);
    c2.show_time();
}

运行结果：                      修改代码：            修改后结果：

 task4： 

#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();
}

运行结果：                

分析：

执行 X x1;时，默认构造函数被调用；

执行 X x2{2049};时，带参数的构造函数被调用；

执行 X x3{x1};时，复制构造函数被调用；

执行 X x4{std::move(x2)};时，移动构造函数被调用;

由运行结果可知，当所有程序执行完毕后，析构函数被调用的，销毁所有对象。

 task5：

#include<iostream>
#include<iomanip>

class Rectangle
{
    public:
        Rectangle(float l=2.0,float w=1.0):length{l},width{w}{}
        Rectangle(const Rectangle& obj):
            length{obj.length},width{obj.width}{}
        ~Rectangle()=default;

        float len() const {return length;}
        float wide() const {return width;} 
        float area() const {return length*width;}
        float circumference() const {return 2*(length+width);}

        void resize(int times);
        void resize(int l_times,int w_times);
    private:
        float length, width;
};

void Rectangle::resize(int times)
{
    length*=times;
    width*=times;
}
void Rectangle::resize(int l_times,int w_times)
{
    length*=l_times;
    width*=w_times;
}

void output(const Rectangle &rect)
{
    using namespace std;

    cout<<"矩阵信息:\n";
    cout<<std::left<<setw(7)<<"长:"<<std::right<<
        fixed<<setprecision(2)<<setw(5)<<rect.len()<<endl;
    cout<<std::left<<setw(7)<<"宽:"<<std::right<<
        fixed<<setprecision(2)<<setw(5)<<rect.wide()<<endl;
    cout<<std::left<<setw(7)<<"面积:"<<std::right<<
        fixed<<setprecision(2)<<setw(5)<<rect.area()<<endl;
    cout<<std::left<<setw(7)<<"周长:"<<std::right<<
        fixed<<setprecision(2)<<setw(5)<<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);
}

运行结果：