Posted by Erwin Moller on 11/30/07 08:34

Tim Roberts wrote:
> bummerland@gmail.com wrote:
>> I have a problem with the function fmod.
>>
>> Why is fmod(5.7, 0.1) = 0.1 ?? Why is it not 0?
>
> Because floating point arithmetic is not exact. The number "5.7" cannot be
> represented exactly in binary. So, it's quite likely that you are really
> computing something like fmod(5.69999999999999, 0.1), and that result would
> be 0.09999999999999, which will print as 0.1.
>
> It's not the function that is broken, I am afraid. It is your
> expectations.

Hi Tim,

The same thought crossed my mind.
But what is the use of fmod if it uses unexcact representations internally?
I mean, if you offer such a function, I would expect it does what it
claims to do (eg in their examples).
And thus NOT use 'normal' floating points representation, but something
that respects 6.0 as 6.0 and not 5.9999999999999.
(I must admit I don't know HOW, but I am sure some smart guy can figure
something out.)

Wouldn't it be better to dump fmod al together?
I mean, what to expect from the function?
What is your opinion?

Regards,
Erwin Moller

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