It has already been said, but it bears repeating since so many people get caught out. There is no such thing as floating point with "reasonably uncomplicated values". Just because a number looks sane in base 10 doesn't mean it's a rational number in binary.

You have a few choices about how to deal with this issue. It does depend on how important this is to you, and what you are trying to accomplish. People writing software for financial institutions will do different things from students just playing with lab results.

• Fixed Point Numbers, part of this thread
• My floating point comparison does not work. Why ?
• Strange rounding Error in Perl

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Update: Hi ikegami, I meant "rational" loosely as a synonym for sane just to avoid repeating myself. I shouldn't have used a word with a well-known mathematical meaning. :-)

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