实践3

4-11

#include<iostream>
using namespace std;
//声明定义类rectangle及其数据和方法
class Rectangle{
    public:                                            //外部接口
        Rectangle(float l,float w);
        float area();                                  //计算面积
        private:                                       //私有数据成员
        float length,width;
};
//类的实现
//构造函数初始化数据成员
Rectangle：：Rectangle(float l,float w){
    length=l,width=w;
}
//计算矩形面积
float Rectangle：：area(){
    return length*width;
}
//主函数实现
int main(){
    float length,width;
    cout<<"enter the length and width of the rectangle:";
    cin>>length>>width;
    Rectangle border(length,width);
    //计算面积并输出
    float result=border.area();
    cout<<"area is"<<result<<endl;
    return 0;
}


4-20

#include<iostream> 
#include<cmath>
using namespace std;
class Complex{
    public:
        Complex(double r0=0,double i0=0);
        void add(Complex &c0);
        void show()
        {
            cout<<"complex:"<<Real<<"+"<<imaginary<<"i"<<endl;
        }
        
    private:
        double Real;
        double imaginary; 

};        
//相关成员函数的实现
Complex::Complex(double r0,double i0)
{
    Real=r0;
    imaginary=i0;
}

void Complex::add(Complex &c0)
{
    c0.Real=Real+c0.Real;
    c0.imaginary=imaginary+c0.imaginary;
}
int main()
{
    Complex c1(3,5);     //用复数3+5i初始化c1
    Complex c2=4.5;      //用实数4.5初始化c2
    c1.show();
    c2.show();
    c1.add(c2);          //将c2与c1相加
    cout<<"additon:"<<endl;
    c1.show();           //输出
    return 0;
}

题目不多，但是发现的问题很多，仅实践这两题还不够。