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| From | Keith Thompson <Keith.S.Thompson+u@gmail.com> |
|---|---|
| Newsgroups | comp.std.c |
| Subject | Re: contradiction about the INFINITY macro |
| Date | 2021-10-09 14:28 -0700 |
| Organization | None to speak of |
| Message-ID | <87o87x6g7o.fsf@nosuchdomain.example.com> (permalink) |
| References | (7 earlier) <87r1d0g0dh.fsf@nosuchdomain.example.com> <861r4xq6a8.fsf@linuxsc.com> <87czog7uso.fsf@nosuchdomain.example.com> <874k9r7419.fsf@nosuchdomain.example.com> <20211009194742$9114@zira.vinc17.org> |
Vincent Lefevre <vincent-news@vinc17.net> writes:
> In article <874k9r7419.fsf@nosuchdomain.example.com>,
> Keith Thompson <Keith.S.Thompson+u@gmail.com> wrote:
>> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>> > Tim Rentsch <tr.17687@z991.linuxsc.com> writes:
>> >> Keith Thompson <Keith.S.Thompson+u@gmail.com> writes:
>> >>> Vincent Lefevre <vincent-news@vinc17.net> writes:
>> >>>> In article <877dewimc9.fsf@nosuchdomain.example.com>,
>> >>>> Keith Thompson <Keith.S.Thompson+u@gmail.com> wrote:
>> >>>>> Vincent Lefevre <vincent-news@vinc17.net> writes:
>> >>>>>
>> >>>>>> In article <87lf3ehy4v.fsf@nosuchdomain.example.com>,
>> >>>>>> Even if FP_INFINITE could be defined conditionally, this would
>> >>>>>> not imply that INFINITY is usable, since for instance, long
>> >>>>>> double may have an infinity but not float.
>> >>>>>
>> >>>>> The standard only defines INFINITY and NAN for type float. I
>> >>>>> think the implication is that it assumes either all floating types
>> >>>>> have NaNs and/or infinities, or none do. That might be a valid
>> >>>>> assumption.
>> >>>>
>> >>>> But the standard doesn't say that explicitly. It even just says
>> >>>> "if and only if the implementation supports quiet NaNs for the
>> >>>> float type". If the intent were to have NaN support for all the
>> >>>> FP types or none, why doesn't it say "... for the floating types"
>> >>>> instead of "... for the float type"?
>> >>>
>> >>> Since the NAN macro is of type float (if it's define), it only makes
>> >>> sense to define it that way. Presumably if an implementation had
>> >>> NaN for float but not for double, it would define NAN.
>> >>
>> >> If float has a NaN then so do double and long double, because of
>> >> 6.2.5 paragraph 10. Similarly for infinity (or infinities).
>> >
>> > Agreed. 6.2.5p10 says:
>> >
>> > There are three real floating types, designated as float, double,
>> > and long double. The set of values of the type float is a subset of
>> > the set of values of the type double; the set of values of the type
>> > double is a subset of the set of values of the type long double.
>> >
>> > (No need to make everyone look it up.)
>
>> I just noticed that leaves open the possibility, for example, that
>> double supports infinity but float doesn't.
>
> This is what I had said above:
>
> "[...] for instance, long double may have an infinity but not float."
Yes. My initial assumption was that the three floating-point types
could independently have or not have infinities. Tim cited 6.2.5p10,
which implies that if float has infinities, then the wider types do
also. (I wonder if the authors had infinities and NaNs in mind when
they wrote that, but the implication is still there.)
If long double has infinities, then float and double may or may not.
If float has infinities, then double and long double must.
--
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Philips
void Void(void) { Void(); } /* The recursive call of the void */
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contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-09-30 01:47 +0000
Re: contradiction about the INFINITY macro Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-09-29 19:05 -0700
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-09-30 11:24 +0000
Re: contradiction about the INFINITY macro Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-09-30 08:38 -0700
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-10-01 09:05 +0000
Re: contradiction about the INFINITY macro Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-01 12:20 -0700
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-10-04 09:26 +0000
Re: contradiction about the INFINITY macro Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-04 10:34 -0700
Re: contradiction about the INFINITY macro Geoff Clare <geoff@clare.See-My-Signature.invalid> - 2021-10-05 13:53 +0100
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-10-06 00:12 +0000
Re: contradiction about the INFINITY macro Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-10-07 07:05 -0700
Re: contradiction about the INFINITY macro Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-07 07:51 -0700
Re: contradiction about the INFINITY macro Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-08 11:41 -0700
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-10-09 19:49 +0000
Re: contradiction about the INFINITY macro Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-09 14:28 -0700
Re: contradiction about the INFINITY macro Jakob Bohm <jb-usenet@wisemo.com.invalid> - 2021-10-01 22:55 +0200
Re: contradiction about the INFINITY macro Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-01 14:26 -0700
Re: contradiction about the INFINITY macro Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-10-08 08:30 -0700
Re: contradiction about the INFINITY macro Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-08 11:40 -0700
Re: contradiction about the INFINITY macro Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-17 21:00 -0800
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-10-09 20:05 +0000
Re: contradiction about the INFINITY macro James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-11 12:40 -0400
Re: contradiction about the INFINITY macro Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-17 21:02 -0800
Re: contradiction about the INFINITY macro Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-10-08 00:02 -0700
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-10-09 20:17 +0000
Re: contradiction about the INFINITY macro James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-11 12:40 -0400
Re: contradiction about the INFINITY macro Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-11 12:39 -0700
Re: contradiction about the INFINITY macro James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-11 21:04 -0400
Re: contradiction about the INFINITY macro Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-10-11 18:33 -0700
Re: contradiction about the INFINITY macro Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-03 12:03 -0800
Re: contradiction about the INFINITY macro Richard Damon <Richard@Damon-Family.org> - 2022-01-03 16:45 -0500
Re: contradiction about the INFINITY macro Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-01-03 14:36 -0800
Re: contradiction about the INFINITY macro James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-04 02:10 -0500
Re: contradiction about the INFINITY macro Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-17 10:09 -0800
Re: contradiction about the INFINITY macro Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-03 11:55 -0800
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-10-26 10:01 +0000
Re: contradiction about the INFINITY macro James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-26 12:53 -0400
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-10-28 09:38 +0000
Re: contradiction about the INFINITY macro James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-28 11:23 -0400
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-10-29 12:12 +0000
Re: contradiction about the INFINITY macro James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-10-30 02:08 -0400
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-11-08 02:44 +0000
Re: contradiction about the INFINITY macro James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-11-08 01:46 -0500
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-11-08 10:56 +0000
Re: contradiction about the INFINITY macro James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-11-08 13:50 -0500
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-11-09 02:48 +0000
Re: contradiction about the INFINITY macro James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-11-09 00:50 -0500
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-11-09 10:12 +0000
Re: contradiction about the INFINITY macro James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-11-09 12:51 -0500
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-11-10 12:48 +0000
Re: contradiction about the INFINITY macro James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-11-10 12:03 -0500
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-11-12 23:17 +0000
Re: contradiction about the INFINITY macro James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-11-12 21:03 -0500
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-11-15 09:18 +0000
Re: contradiction about the INFINITY macro James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-11-15 14:25 -0500
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-11-16 01:17 +0000
Re: contradiction about the INFINITY macro James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-11-16 10:29 -0500
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-12-08 10:09 +0000
Re: contradiction about the INFINITY macro Derek Jones <derek@NOSPAM-knosof.co.uk> - 2021-11-16 11:32 +0000
Re: contradiction about the INFINITY macro James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-11-16 10:35 -0500
Re: contradiction about the INFINITY macro Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-11-09 07:13 -0800
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-11-10 13:16 +0000
Re: contradiction about the INFINITY macro Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-11-10 08:02 -0800
Re: contradiction about the INFINITY macro Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-11-10 15:01 -0800
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-11-13 00:30 +0000
Re: contradiction about the INFINITY macro Thomas Koenig <tkoenig@netcologne.de> - 2021-12-02 22:14 +0000
Re: contradiction about the INFINITY macro Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-03 12:48 -0800
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-11-12 23:55 +0000
Re: contradiction about the INFINITY macro Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-11-15 07:59 -0800
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-11-15 23:39 +0000
Re: contradiction about the INFINITY macro James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-11-15 20:00 -0500
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-11-16 01:28 +0000
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-11-16 01:57 +0000
Re: contradiction about the INFINITY macro James Kuyper <jameskuyper@alumni.caltech.edu> - 2021-11-16 09:52 -0500
Re: contradiction about the INFINITY macro Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-11-16 19:00 -0800
Re: contradiction about the INFINITY macro Vincent Lefevre <vincent-news@vinc17.net> - 2021-12-08 10:56 +0000
Re: contradiction about the INFINITY macro Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-03 12:56 -0800
Re: contradiction about the INFINITY macro James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-03 22:45 -0800
Re: contradiction about the INFINITY macro Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-17 05:35 -0800
Re: contradiction about the INFINITY macro Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-09-30 03:20 +0100
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