using System;

//using System.Linq;

//using System.Collections;

public class Program

{

    // function format

    // <visibility> <return type> <Function Name> <(list or parameter)>

    // { <function body> }

    public void my_swap (int x, int y){

        int temp;

        temp = x;

        x = y;

        y = temp;

        Console.WriteLine(x.ToString("d5"));

    }

    public double getCircleArea(double radius){

        double a = 3.14*radius*radius;

        return a;

    }

    public double getRectArea(double w, double h){

        return h*w;

    }

    public static void Main()

    {

        Console.WriteLine("Hello World");

    }

    Circle c1 = new Circle();

    Circle c2 = new Circle(5.0, "blue");

}

​

// every shape has color, area, perimeter, name, etc.

public abstract class Shape{

    public string name;

    public string color;

    public abstract double getArea();

    //no body = abstract function which will make it an abstract class

    // abstract : can not create instance of abstract class

    // so you can not do --> Shape S1 = new Shape();

    public abstract double getPerimeter();

}

​

// use colon to inherit something

public class Circle : Shape{

    // attributes off circle - list of varibles describe each individual circle

    public double radius;

    public string color;

    //list of functions -- behaviors/ actions of the circle

    // every class must have one or more CONSTRUCTOR function(s)

    //contructor is a very special function : 

    //    -it has the same name as the class

    //    -it DOESN'T have a return type

    //    -it has ZERO or multiple parameters

    //    - the constructor that has zero parameters is reffered to as the default

    //    - we can have multiple constructor functions in a class

    public Circle(){

        radius = 1.0;

        color = "white";

        // every circle will hacve a radius of 1 and be white

    }

    public Circle(double r, string c){

        radius = r;

        color = c;

        // each circle can have its own radius and color

        // tis customized

    }

    public double getArea(double radius){

        double a = 3.14*radius*radius;

        return a;

    }

    // both getCircleArea and getPerimeter have parameter double radius - 

    //     you can keep it there or omit it from one or both, it wont matter or change anything

    public double getPerimeter(double radius){

        return 2*radius*3.14;

    }

    public double getRadius(){

        return radius;

    }

    public void setCircleRadius( double r){

        radius = r;

    }

    public void setCircleColor(string c){

        color = c;

    }

}

​

public class Rectangle{

    public double w;

    public double h;

    public double getArea(){

        return w*h;

    }

}