2. Safely_Comparing_Floats

/* Write a program that safely compares floating-point numbers (double) with precision
 * eps = 0.000001. Note that we cannot directly compare two floating-point numbers a and b
 * by a==b because of the nature of the floating-point arithmetic.
 * Therefore, we assume two numbers are equal if they are more closely
 * to each other than a fixed constant eps. */

namespace _13.ComparingFloats
{
    using System;

    public class SafelyComparingFloats
    {
        private const double EPS = 0.000001d;

        public static void Main(string[] args)
        {
            checked
            {
                Console.Write("Enter the First real number: ");
                double numA = double.Parse(Console.ReadLine());
                Console.Write("Enter the Second real number: ");
                double numB = double.Parse(Console.ReadLine());

                if (!double.Equals(numA, numB))
                {
                    if (numA < 0 && numB < 0)
                    {
                        numA = Math.Abs(numA);
                        numB = Math.Abs(numB);
                    }

                    double difference = Math.Abs(numA - numB);
                    if (difference < EPS)
                    {
                        Console.WriteLine("These two Float-Point numbers IS EQUALS !");
                        Console.WriteLine("The Difference is too small: {0:F8} !", difference);
                    }
                    else
                    {
                        Console.WriteLine("These two Float-Point numbers is NOT EQUALS !");
                        Console.WriteLine("The Difference is: {0} !", difference);
                    }
                }
                else
                {
                    Console.WriteLine("These two Float-Point numbers IS EQUALS !");
                }
            }
        }
    }
}