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Re: [PATCH v3] Add nextup and nextdown math functions
- From: Joseph Myers <joseph at codesourcery dot com>
- To: Rical Jasan <ricaljasan at pacific dot net>
- Cc: Rajalakshmi Srinivasaraghavan <raji at linux dot vnet dot ibm dot com>, <libc-alpha at sourceware dot org>, "Paul E. Murphy" <murphyp at linux dot vnet dot ibm dot com>
- Date: Wed, 8 Jun 2016 12:40:32 +0000
- Subject: Re: [PATCH v3] Add nextup and nextdown math functions
- Authentication-results: sourceware.org; auth=none
- References: <201606011211 dot u51C9sVN019582 at mx0a-001b2d01 dot pphosted dot com> <574FE5C6 dot 6040303 at pacific dot net> <alpine dot DEB dot 2 dot 20 dot 1606022330330 dot 9542 at digraph dot polyomino dot org dot uk> <201606061715 dot u56HEkNN001197 at mx0a-001b2d01 dot pphosted dot com> <57567324 dot 6030301 at pacific dot net> <alpine dot DEB dot 2 dot 20 dot 1606071711260 dot 10967 at digraph dot polyomino dot org dot uk> <5757BF47 dot 4070605 at pacific dot net>
On Tue, 7 Jun 2016, Rical Jasan wrote:
> I don't believe quiet NaNs are mentioned, though, so if that just means
> a normal NaN that doesn't make noise by signalling like a sNaN, it might
> not hurt to introduce that language in the Infinity and NaN section.
NaNs are quiet by default, as per the usage in the C standard. Yes, maybe
the glibc manual needs to say a bit more there.
> nextup(-Inf) is more interesting :), as well as the subnormal, but is
> the zero behaviour you just described abnormal in some way? That seems
The point is that it's not about an ordering (-DBL_TRUE_MIN, -0.0, 0.0,
DBL_TRUE_MIN) that has both -0.0 and +0.0 (like for the totalorder
function in TS 18661-1) and goes from one to the other - but about going
to the next value that is strictly greater or less than the argument
(depending on the function). And saying that then leaves the choice of
-0.0 or +0.0 as ambiguous, so it needs to be specified.
Joseph S. Myers