Date: Fri, 12 Sep 2014 15:41:12 -0700 From: Steve Kargl <sgk@troutmask.apl.washington.edu> To: enh <enh@google.com> Cc: freebsd-numerics@freebsd.org Subject: Re: lgamma_r and lgammaf_r return the wrong sign for -0.f Message-ID: <20140912224112.GA97578@troutmask.apl.washington.edu> In-Reply-To: <CAJgzZoruuVxLJ1sdue-NmvxKJwW7WKrY6GsopKMQi3Us4goxCQ@mail.gmail.com> References: <CAJgzZopa-d=eR7zkqhffsjMY0NEavhqDA-B3V9bQdaJd6BMO2A@mail.gmail.com> <20140912220544.GA96714@troutmask.apl.washington.edu> <CAJgzZoruuVxLJ1sdue-NmvxKJwW7WKrY6GsopKMQi3Us4goxCQ@mail.gmail.com>
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On Fri, Sep 12, 2014 at 03:17:02PM -0700, enh via freebsd-numerics wrote: > On Fri, Sep 12, 2014 at 3:05 PM, Steve Kargl > > F.9.5.3 The lgamma functions > > -- lgamma(1) returns +0. > > -- lgamma(2) returns +0. > > -- lgamma(x) returns +inf and raises the ``divide-by-zero'' floating-point > > exception for x a negative integer or zero. > > -- lgamma(-inf) returns +inf. > > -- lgamma(+inf) returns +inf. > > > > See the 3rd bullet. -0 is 0 and -0 is a negative integer. Of course, neither POSIX nor ISO C specify lgamma_r() only lgamma. I just spent too much time on the 'divide-by-zero' bug, and conflated that with signgam. > > POSIX appears to defer to ISO C. n1570.pdf (committe draft for C11) > > has (almost?) identical text. > > > >> patch below (whitespace mangled courtesy of gmail). i'd prefer to wait > >> for this to be fixed in FreeBSD and pull down the fix rather than just > >> fix it locally. > > > > I have a bigger patch coming with ld80 and ld128 version of lgammal > > and lgammal_r. > > sorry, i haven't even looked at the *l variants. I only just finished writing the *l variants. It took me a long time to unwind the comments in e_lgamma_r.c, so that I could write the long double versions. -- Steve
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