From: "Stephan Kämper" <Stephan.Kaemper@...>
Date: 2004-05-13T05:38:53+09:00
Subject: Re: Major Addition Bug?

Hal Fulton wrote:
> 
> Seriously, I think it's a matter of trying to store an infinite
> number of digits in a finite number of bits.
> 
> For a daily life example: How many digits does it take to store
> "1/3" exactly?  0.333333...

SCNR, but:

irb(main):001:0> 1/3
=> 0

*That* result fits into a single bit. ;-)

But in general there's not much to add to this thread, but to summarize it:

- For financial calculations use specialised classes (which should
   handle different currencies, BTW)
- If you *need* a higher number of digits use BigDecim (which is
    documented in the 'Ruby Standard Library Documentation' available
    at http://www.ruby-doc.org/downloads/stdlib/ )
- Never, repeat *never* compare floats with == or other operators like
   that. Define some kind of accuracy, say epsilon and use a usual metric
   like this:
         ( a_value - something_else ).abs < epsilon
- Don't use == to compare floats and last but not least
- Comparing floats with == is a Bad Thing.

Well, that's it - more or less.

Happy rubying,

Stephan