On 30 Jun 2010, at 15:56, Frederick Bartram wrote:
> Hope that I am not being too pedantic but imo you should never test for
> 'equality' ('==') when using machine real data types.
Sometimes you really do want binary equivalence, and in that case == may be the
right thing to use. Normally, though, you're quite right, you need to be
careful with floating point comparisons (not just equality tests, actually;
sometimes for greater-than or less-than comparisons you might want two floats
to be "un-ordered" if they're close in value).
I thought it'd be useful to link to the excellent "What Every Computer
Scientist Should Know About Floating-Point Arithmetic", since that's usually
the best thing to give to people who are worrying about this kind of thing:
<http://dlc.sun.com/pdf/800-7895/800-7895.pdf>
<http://docs.sun.com/source/806-3568/ncg_goldberg.html>
Anyone who hasn't read it should.
Kind regards,
Alastair.
--
http://alastairs-place.net
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