第一次实验

实验一：类和对象

Task 2

#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<<"constrctor 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;
    
}

测试结果：

修改数据后：

Task 3

#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();
    
    return 0;
}

测试结果：

修改数据后：

Task 4

#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();
    
    return 0;
}

测试结果：

构造函数：

  (1)X x1：默认构造函数X()被调用

  (2)X x2{2022}：构造函数X(int m)被调用，将2022赋值给x2.data

  (3)X x3{x1}：复制构造函数被调用，将x1.data赋值给x3.data

  (4)X x4{std::move(x2)}：移动构造函数被调用，将x2.data赋值给x4.data 

析构函数：

  析构函数被调用的顺序与构造函数相反，x4首先调用析构函数，其次x3，然后x2，最后x1

  即在程序结束前，析构函数被调用，并依次对x4,x3,x2,x1进行销毁

Task 5

#include<iostream>
#include<iomanip>
class Rectangle{
    public:
        Rectangle(double l=2.0,double w=1.0):length{l},width{w}{};
        Rectangle(const Rectangle& obj):length{obj.length},width{obj.width}{};
        ~Rectangle()=default;
        double len() const{return length;}
        double wide() const{return width;}
        double area() const{return length*width;}
        double circumference() const{return (length+width)*2;}
        void resize(int times);
        void resize(int l_times,int w_times);
    private:
        double 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<<"矩形信息：\n";
    cout<<fixed<<setprecision(2);
    cout<<std::left<<setw(8)<<"长："<<rect.len()<<endl;
    cout<<std::left<<setw(8)<<"宽: "<<rect.wide()<<endl;
    cout<<std::left<<setw(8)<<"面积:"<<rect.area()<<endl;
    cout<<std::left<<setw(8)<<"周长:"<<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);
}

测试结果：