Addition of Double values inconsistent

Question

I came across following issue while developing some engineering rule value engine using eval(...) implementation.

    Dim first As Double = 1.1
    Dim secon         


        

Answer 1

You are not adding decimals - you are adding up doubles.

Not all doubles can be represented accurately in a computer, hence the error. I suggest reading this article for background (What Every Computer Scientist Should Know About Floating-Point Arithmetic).

Use the Decimal type instead, it doesn't suffer from these issues.

Dim first As Decimal = 1.1
Dim second As Decimal = 2.2
Dim sum As Decimal= first + second
 If (sum = 3.3) Then
    Console.WriteLine("Matched")
Else
    Console.WriteLine("Not Matched")
End If