标准C++命名空间的使用

shape.h

/*
    Circle
*/

namespace G_Shape
{
    class Circle
    {
    public:
        double calculate_perimeter(double radius);
        double calculate_area(double radius);
    private:
        double radius;
    };

    /*
        Rectangle
    */
    class Rectangle
    {
    public:
        double calculate_perimeter(double width, double height);
        double calculate_area(double width, double height);
    private:
        double width;
        double height;
    };
}

shape.cpp

#include "shape.h"

using namespace G_Shape;

#define PI 3.14159

/*
    Circle
*/

double Circle::calculate_perimeter(double radius)
{
    return 2 * PI * radius;
}

double Circle::calculate_area(double radius)
{
    return PI * radius * radius;
}


/*
    Rectangle
*/

double Rectangle::calculate_perimeter(double width, double height)
{
    return 2 * (width + height);
}

double Rectangle::calculate_area(double width, double height)
{
    return width * height;
}

mainframe.cpp

#include <iostream>
#include "draw/shape.h"

using namespace std;
using namespace G_Shape;

int main()
{
    //Circle    
    double radius;

    cout<< "Please input radius of the circle:";
    cin>>radius;

    Circle c;
    cout << "Circle Perimeter: " << c.calculate_perimeter(radius) <<endl;
    cout << "Circle Area: " << c.calculate_area(radius) <<endl;

    //Rectangle
    double width, height;

    cout<< "Please input width of the rectangle:";
    cin>>width;
    cout<< "Please input height of the rectangle:";
    cin>>height;

    Rectangle r;
    cout << "Rectangle Perimeter: " << r.calculate_perimeter(width, height) <<endl;
    cout << "Rectangle Area: " << r.calculate_area(width, height) <<endl;
    
    return 0;
}

运行结果:

david@ubuntu:~/MyProject/Hades$ ./mainframe.exe
Please input radius of the circle:5
Circle Perimeter: 31.4159
Circle Area: 78.5397
Please input width of the rectangle:4
Please input height of the rectangle:5
Rectangle Perimeter: 18
Rectangle Area: 20