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Groups > comp.lang.c > #168903
| From | Keith Thompson <Keith.S.Thompson+u@gmail.com> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: structs passed by copy |
| Date | 2023-01-22 16:01 -0800 |
| Organization | None to speak of |
| Message-ID | <87o7qqglva.fsf@nosuchdomain.example.com> (permalink) |
| References | (4 earlier) <1btu0jojlm.fsf@pfeifferfamily.net> <87edrnifxn.fsf@nosuchdomain.example.com> <tqk855$386s5$2@dont-email.me> <87sfg2gszl.fsf@nosuchdomain.example.com> <tqkcal$393b1$1@dont-email.me> |
James Kuyper <jameskuyper@alumni.caltech.edu> writes:
> On 1/22/23 16:27, Keith Thompson wrote:
>> James Kuyper <jameskuyper@alumni.caltech.edu> writes:
> ...
>>> Just as it is extremely common for numbers to be pure-real, with no
>>> imaginary part, it is not uncommon, when doing physics or engineering
>>> using complex values, to have some of those quantities being calculated
>>> to be guaranteed to be pure imaginary. Storing such quantities using
>>> _Imaginary types reduces the space required by a factor of 2, which can
>>> be important if you have huge arrays of them (not an uncommon feature of
>>> physics/engineering programs). More importantly, I think, is that use of
>>> such types should enable warnings about questionable uses of such types,
>>> such as taking the Real part of them.
>>>
>>> It's certainly not impossible to work with such quantities efficiently
>>> without using the _Imaginary types - before the introduction of those
>>> types, they could have been stored as real values, with a comment
>>> indicating that these real values are the imaginary component of the
>>> actual value. However, making _Imaginary a part of the declaration of
>>> such objects is better than relying upon people to notice such a comment.
>>
>> Thanks, I didn't know that.
>>
>> Given that imaginary types are useful, I wonder why they're not
>> widely supported. Neither gcc 12.2.0 nor clang 15.0.0 supports
>> `_Imaginary double`.
>>
>> And both predefine __STDC_IEC_559_COMPLEX__, which if I'm reading
>> Annex G correctly implies that they're required to support imaginary
>> types.
I was wrong about this; see below.
> I said that they could be useful. I didn't address how useful they would
> be. I don't imagine that the usefulness is great. I hope the committee
> had some evidence of actual demand for such a feature before deciding to
> add it to the language.
There are still a few things I'm curious about:
Why did the committee choose to make complex numbers mandatory and
imaginary numbers optional? I wouldn't expect imaginary numbers
to be very difficult to implement once you have complex numbers.
Nor would I expect users of one C implementation to have a greater
need for them than users of another (which would have been a
reasonable basis for making them optional).
Have any C compilers implemented _Imaginary? (If not, it seems
like a failed experiment.)
A minor note: N1256 (C99) has a footnote in 7.3 referring
to "informative annex G". N1570 (C11) has the same footnote.
But Annex G is informative in C99, normative in C11.
BTW, I was wrong about one thing: Support for _Imaginary is optional
even for an implementation that predefines __STDC_IEC_559_COMPLEX__.
`#ifdef _Imaginary_I` can be used to detect whether an implementation
supports imaginary types.
--
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for XCOM Labs
void Void(void) { Void(); } /* The recursive call of the void */
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structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-01-20 10:41 -0800
Re: structs passed by copy gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-20 19:01 +0000
Re: structs passed by copy Anton Shepelev <anton.txt@gmail.com> - 2023-01-20 23:01 +0300
Re: structs passed by copy gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-20 21:28 +0000
Re: structs passed by copy Kaz Kylheku <864-117-4973@kylheku.com> - 2023-01-21 09:14 +0000
Re: structs passed by copy Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2023-01-21 10:58 -0700
Re: structs passed by copy gazelle@shell.xmission.com (Kenny McCormack) - 2023-01-21 18:00 +0000
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-21 16:14 -0800
Re: structs passed by copy James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-01-22 16:00 -0500
Re: structs passed by copy "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-22 13:07 -0800
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-22 13:27 -0800
Re: structs passed by copy "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-22 13:51 -0800
Re: structs passed by copy "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-22 13:51 -0800
Re: structs passed by copy James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-01-22 17:11 -0500
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-22 16:01 -0800
Re: structs passed by copy Richard Damon <Richard@Damon-Family.org> - 2023-01-22 21:22 -0500
Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-01-23 10:46 +0100
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-23 12:15 -0800
Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-01-23 21:47 +0100
Re: structs passed by copy Michael S <already5chosen@yahoo.com> - 2023-01-23 13:21 -0800
Re: structs passed by copy Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-23 23:49 +0000
Re: structs passed by copy Michael S <already5chosen@yahoo.com> - 2023-01-24 02:46 -0800
Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-24 04:18 -0800
Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-24 04:45 -0800
Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-24 04:54 -0800
Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-24 05:26 -0800
Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-24 05:38 -0800
Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-24 05:53 -0800
Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-24 06:20 -0800
Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-24 06:56 -0800
Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-24 07:17 -0800
Re: structs passed by copy Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-24 12:56 +0000
Re: structs passed by copy Michael S <already5chosen@yahoo.com> - 2023-01-24 07:29 -0800
Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-01-23 15:44 -0800
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-23 16:37 -0800
Re: structs passed by copy James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-01-23 20:13 -0500
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-23 17:58 -0800
Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-01-24 07:53 -0800
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-24 11:14 -0800
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-24 12:02 -0800
Re: structs passed by copy Phil Carmody <pc+usenet@asdf.org> - 2023-01-25 10:18 +0200
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-25 10:53 -0800
Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-01-29 13:30 -0800
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-29 17:42 -0800
Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-02-17 07:19 -0800
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-02-17 09:35 -0800
Re: structs passed by copy John Forkosh <forkosh@panix.com> - 2023-01-30 04:24 +0000
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-29 21:10 -0800
Re: structs passed by copy Michael S <already5chosen@yahoo.com> - 2023-01-30 13:55 -0800
Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-02-17 05:57 -0800
Re: structs passed by copy James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-01-21 05:00 -0500
Re: structs passed by copy Anton Shepelev <anton.txt@gmail.com> - 2023-01-21 23:00 +0300
Re: structs passed by copy Richard Damon <Richard@Damon-Family.org> - 2023-01-21 17:10 -0500
Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-01-20 18:12 -0800
Re: structs passed by copy antispam@math.uni.wroc.pl - 2023-01-21 02:28 +0000
Re: structs passed by copy Blue-Maned_Hawk <bluemanedhawk@gmail.com> - 2023-01-20 14:09 -0500
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-20 11:26 -0800
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-20 11:22 -0800
Re: structs passed by copy Bart <bc@freeuk.com> - 2023-01-20 20:16 +0000
Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-01-20 19:16 -0800
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-01-20 21:08 -0800
Re: structs passed by copy Bart <bc@freeuk.com> - 2023-01-21 13:30 +0000
Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-22 10:27 -0800
Re: structs passed by copy Richard Damon <Richard@Damon-Family.org> - 2023-01-20 21:35 -0500
Re: structs passed by copy "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-20 19:01 -0800
Re: structs passed by copy "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-21 17:01 -0800
Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-01-21 14:59 +0100
Re: structs passed by copy Opus <ifonly@youknew.org> - 2023-01-21 19:59 +0100
Re: structs passed by copy Michael S <already5chosen@yahoo.com> - 2023-01-21 16:55 -0800
Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-01-22 02:32 -0800
Re: structs passed by copy Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-22 15:54 +0000
Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-22 09:17 -0800
Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-22 09:56 -0800
Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-22 10:19 -0800
Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-22 11:01 -0800
Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-22 11:08 -0800
Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-22 11:17 -0800
Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-01-22 13:27 -0800
Re: structs passed by copy "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-22 13:04 -0800
Re: structs passed by copy Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-22 21:43 +0000
Re: structs passed by copy "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-22 14:10 -0800
Re: structs passed by copy Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-22 22:29 +0000
Re: structs passed by copy "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-01-22 14:39 -0800
Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-01-22 19:06 -0800
Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-01-23 10:54 +0100
Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-01-22 19:00 -0800
Re: structs passed by copy Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-01-23 12:14 +0000
Re: structs passed by copy Jorgen Grahn <grahn+nntp@snipabacken.se> - 2023-02-11 19:35 +0000
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-02-11 15:08 -0800
Re: structs passed by copy Öö Tiib <ootiib@hot.ee> - 2023-02-11 15:56 -0800
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-02-11 16:32 -0800
Re: structs passed by copy James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-02-12 01:23 -0500
Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-02-12 11:24 +0100
Re: structs passed by copy Vir Campestris <vir.campestris@invalid.invalid> - 2023-02-12 22:11 +0000
Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-02-13 10:25 +0100
Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-02-13 06:41 -0800
Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-02-13 06:50 -0800
Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-02-13 17:22 +0100
Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-02-13 10:47 -0800
Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-02-13 21:50 +0100
Re: structs passed by copy bart c <bart4858@gmail.com> - 2023-02-15 17:14 -0800
Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-02-16 10:53 +0100
Re: structs passed by copy scott@slp53.sl.home (Scott Lurndal) - 2023-02-16 15:22 +0000
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-02-12 11:04 -0800
Re: structs passed by copy Öö Tiib <ootiib@hot.ee> - 2023-02-12 12:41 -0800
Re: structs passed by copy Andrey Tarasevich <andreytarasevich@hotmail.com> - 2023-02-16 22:49 -0800
Re: structs passed by copy "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2023-02-11 17:49 -0800
Grammar nitpick (Was: structs passed by copy) gazelle@shell.xmission.com (Kenny McCormack) - 2023-02-12 06:30 +0000
Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-03-06 09:32 -0800
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-03-06 09:58 -0800
Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-03-06 11:30 -0800
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-03-06 12:59 -0800
Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-02-15 01:52 -0800
Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-02-16 05:20 -0800
Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-02-16 16:49 +0100
Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-02-26 08:12 -0800
Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-02-28 05:38 -0800
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-02-28 14:18 -0800
Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-03-01 05:02 -0800
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-03-01 10:23 -0800
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-03-01 10:42 -0800
Re: structs passed by copy bart c <bart4858@gmail.com> - 2023-03-01 15:13 -0800
Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-03-02 04:17 -0800
Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-03-05 04:17 -0800
Re: structs passed by copy fir <profesor.fir@gmail.com> - 2023-03-05 04:55 -0800
Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-03-02 10:48 +0100
Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-03-02 04:07 -0800
Re: structs passed by copy David Brown <david.brown@hesbynett.no> - 2023-03-02 15:08 +0100
Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-03-02 09:22 -0800
Re: structs passed by copy gazelle@shell.xmission.com (Kenny McCormack) - 2023-03-01 13:34 +0000
Re: structs passed by copy Richard Damon <Richard@Damon-Family.org> - 2023-03-01 21:42 -0500
Re: structs passed by copy Tim Rentsch <tr.17687@z991.linuxsc.com> - 2023-03-06 09:36 -0800
Re: structs passed by copy Maciej Zelma <maciej.projectmanager@gmail.com> - 2023-02-17 14:10 -0800
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-02-17 15:45 -0800
Re: structs passed by copy scott@slp53.sl.home (Scott Lurndal) - 2023-02-18 00:12 +0000
Re: structs passed by copy bart c <bart4858@gmail.com> - 2023-02-18 02:33 -0800
Re: structs passed by copy James Kuyper <jameskuyper@alumni.caltech.edu> - 2023-02-18 00:44 -0500
Re: structs passed by copy Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2023-02-17 22:21 -0800
Re: structs passed by copy Bonita Montero <Bonita.Montero@gmail.com> - 2023-03-01 18:00 +0100
Re: structs passed by copy Thiago Adams <thiago.adams@gmail.com> - 2023-03-01 09:18 -0800
Re: structs passed by copy Bonita Montero <Bonita.Montero@gmail.com> - 2023-03-05 14:05 +0100
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