3-4 计算长方形的周长和面积

Problem Description

通过本题的练习可以掌握拷贝构造函数的定义和使用方法；

设计一个长方形类Rect，计算长方形的周长与面积。类中有私有数据成员Length(长)、Width(宽)，由具有缺省参数值的构造函数对其初始化，函数原型为：Rect(double Length=0, double Width=0); 再为其定义拷贝构造函数，形参为对象的常引用，函数原型为：Rect(const Rect &); 编写主函数，创建Rect对象r1初始化为长、宽数据，利用r1初始化另一个Rect对象r2，分别输出对象的长和宽、周长和面积。

 

 

要求： 创建对象 Rect r1(3.0,2.0),r2(r1);

Input

输入两个实数，中间用一个空格间隔；代表长方形的长和宽

Output

共有6行 ；
分别输出r1的长和宽； r1的周长； r1的面积；r2的长和宽； r2的周长； r2的面积；注意单词与单词之间用一个空格间隔

Example Input

56 32

Example Output

the length and width of r1 is:56,32the perimeter of r1 is:176the area of r1 is:1792the length and width of r2 is:56,32the perimeter of r2 is:176the area of r2 is:1792

Hint

 

输入 -7.0 -8.0

输出

the length and width of r1 is:0,0

the perimeter of r1 is:0

the area of r1 is:0

the length and width of r2 is:0,0

the perimeter of r2 is:0

the area of r2 is:0

Author

 黄晶晶

#include<iostream>using namespace std;class Rect{public:    Rect(double xx = 0, double yy = 0);    Rect(const Rect &r2);    void display();    void display1();private:    double l, w;};Rect::Rect(const Rect &r2){    l = r2.l;    w = r2.w;}Rect:: Rect(double xx, double yy){    l = xx;    w = yy;}void Rect :: display(){   cout<<"the length and width of r1 is:"<<l<<","<<w<<endl;        cout<<"the perimeter of r1 is:"<<(l + w) * 2 <<endl;        cout<<"the area of r1 is:"<<l*w<<endl;}void Rect :: display1(){    cout<<"the length and width of r2 is:"<<l<<","<<w<<endl;        cout<<"the perimeter of r2 is:"<<(l + w) * 2 <<endl;        cout<<"the area of r2 is:"<<l*w<<endl;}int main(){    double x, y;    cin>>x>>y;    if(x < 0 || y < 0)    {        x = 0; y = 0;    }    Rect r1(x, y);    Rect r2(r1);    r1.display();    r2.display1();    return 0;}