PV913PolygonClassDemo

#include <iostream>
#include <vector>
#include <string>
#include <math.h>

class Polygon
{
protected:
    std::vector<float> sides;

public:
    Polygon& addSide(float size) { sides.push_back(size); return *this; };
    Polygon& setSide(int sideId, float size)
    {
        sides[sideId] = size; return *this;
    };
    float getSide(int sideId)const { return sides[sideId]; };
    virtual float perimeter()const
    {
        float per{ 0 };
        for (const auto & side : sides)
        {
            per += side;
        }
        return per;
    };
    virtual float area()const { return 0; };

    const Polygon& sidesInfo()const
    {
        for (int i{ 0 }; i < sides.size(); ++i)
        {
            std::cout << " Side " << char('A' + i) << " is " << sides[i] << " long\n";
        }
        return *this;
    }

    std::string name()const
    {
        std::string nm{ typeid(*this).name() }; //"class Polygon"
        return nm.substr(5);
    }

    const Polygon& info()const
    {
        std::cout << name() << ":\n"
            << " Perimeter: " << perimeter()
            << " Area: " << area() << '\n';
        sidesInfo();
        std::cout << '\n';

        return *this;
    }

};

class Rectangle : public Polygon
{
public:
    Rectangle(float sideA, float sideB) { addSide(sideA); addSide(sideB); };
    virtual float perimeter()const override{ return Polygon::perimeter() * 2; };
    virtual float area()const  override { return getSide(0) * getSide(1); }
};

class Square : public Rectangle
{
public:
    Square(float sideA) : Rectangle{ sideA, sideA } {};
};

class Triangle : public Polygon
{
public:
    Triangle(float sideA, float sideB, float sideC)
    {
        addSide(sideA).addSide(sideB).addSide(sideC);
    };
    virtual float area()const override
    {
        const float p{ perimeter() / 2 };
        return sqrt(p * (p - getSide(0)) * (p - getSide(1)) * (p - getSide(2)));
    }
};


int main()
{
    Polygon* polygons[]{ new Rectangle{4,5}, new Square{6}, new Triangle{3,4,5} };

    for (const auto& polygon : polygons)
    {
        polygon->info();

        delete polygon;
    };

    return 0;
}