add two double given wrong result

Question

I\'m using the following piece of code and under some mysterious circumstances the result of the addition is not as it\'s supposed to be:

double _west = 9.482935         


        

Answer 1

You cannot represent every floating point number in the decimal system with a floating point in a binary system accurately, this isn't even directly related to how "small" the decimal number is, some numbers just don't "fit" in base-2 nicely.

Using a longer bit width can help in most cases, but not always.

To specify your constants in Decimal (128-bit floating point ) precision, use this declaration:

decimal _west = 9.482935905456543m;
decimal _off = 0.00000093248155508263153m;
decimal _lon = _west + _off;