[Mono-dev] Double multiplication

[Vladimir Dimitrov]

Today was one of the strangest days that I had recently. I woke up today to
discover another way of thinking about numbers ::-)

 

To cut the long story short let me ask a simple question. Do you know the
result that the following code will produce as a console output:

 

using System;

 

namespace MultTest

{

    class Program

    {

        static void Main (string [] args)

        {

            double d1 = 127.2;

            double d2 = 128.2;

            double hundred = 100;

 

            Console.WriteLine ("{0} * {1} = {2}", d1, hundred, Math.Floor
(d1 * 100));

            Console.WriteLine ("{0} * {1} = {2}", d2, hundred, Math.Floor
(d2 * 100));

            Console.ReadKey ();

        }

    }

}

 

Well what I get from it is:

 

127.2 * 100 = 12720

128.2 * 100 = 12819

 

Am I the only one that thinks this is wrong? The things are even worse
because I noticed the problem on MS.NET first, and then on Mono and since
Microsoft is very unlikely to care about what I have to say, I decided that
you guys can be a lot more helpful.

 

Thanks

 Vladimir Dimitrov

 

P.S. I tried it on different machines Core 2 Duo (T7200) and Pentium 4.

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