using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;

namespace ForDZ
{
    class Program
    {
        static double circle(int r, double x)
        {
            if (x > r) throw new ApplicationException("nan");
            return 2 * Math.Sqrt(r * r - x * x);
        }

        delegate double function(int r, double x);

        static double integral(function f, int r, double accuracy)
        {
            Console.WriteLine("Processing: 0%");
            double res = 0;

            double startX = -r + accuracy;
            double endX = r - accuracy;

            long time = (long)((endX - startX) / accuracy);
            long oneprocent = time / 100;
            long counter =  0;

            for (double i = startX; i < endX; i += accuracy)
            {
                res += ((f(r, i) + f(r, i + accuracy)) / 2) * accuracy;
                counter++;
                if (counter % oneprocent == 0)
                {
                    Console.Clear();
                    Console.WriteLine("Processing: {0}%", counter / oneprocent);
                }

            }
            Console.Clear();

            return res;
        }

        static void Main(string[] args)
        {
            int radius = 1;
            double accuracy = 1E-10;
            double areaPI = Math.PI * radius * radius;
            double areaINT = integral(new function(circle), radius, accuracy);

            Console.WriteLine("Интегральная площадь: {0} \nПлощадь через пи: {1} \nРазница: {2}", areaINT, areaPI, Math.Abs(areaINT - areaPI));

            //Console.WriteLine("end");
            Console.ReadKey();
        }
    }
}