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From Sébastien Brisard <sebastien.bris...@m4x.org>
Subject Re: [math] UnexpectedNegativeIntegerException
Date Thu, 23 Aug 2012 10:35:18 GMT
Hi Gilles,

2012/8/23 Gilles Sadowski <gilles@harfang.homelinux.org>:
> On Thu, Aug 23, 2012 at 10:05:10AM +0200, Sébastien Brisard wrote:
>> Hi Luc,
>>
>> 2012/8/23 Luc Maisonobe <Luc.Maisonobe@free.fr>:
>> > Le 23/08/2012 05:16, Sébastien Brisard a écrit :
>> >> Hi,
>> >> in MATH-849, I have proposed an implementation of Gamma(x)
>> >> (previously, class Gamma had only logGamma(x)). Gamma(x) is not
>> >> defined for x negative integer. In such instances, I would like to
>> >> throw an exception instead of returning Double.NaN. However, creating
>> >> a new exception in o.a.c.m.exception seems exagerated, since it's very
>> >> unlikely that this exception should be used elsewhere (or maybe).
>> >> Should I define a nested exception instead [1]?
>> >>
>> >> What do you think of the name "UnexpectedNegativeIntegerException"? It
>> >> does not really match the pattern of already defined exceptions, but I
>> >> can't find a better name.
>> >
>> > Don't we already have NotPositiveException?
>> >
>> > Luc
>> >
>> We do, but Gamma is defined for all negative values, except integer ones...
>
> I think that in some circumstances, it might be useful to not throw
> exceptions...
> FastMath's "log" returns NaN for negative input.
>
then I guess that logGamma(x) should also return NaN if x <= 0?
I have to say I do not really like this option. My life would
sometimes be much easier if NaNs didn't exist... the good old days of
the "floating-point error".

Sébastien


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