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| From | Keith Thompson <kst-u@mib.org> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: determines if it is a signed type |
| Date | 2015-05-18 08:00 -0700 |
| Organization | None to speak of |
| Message-ID | <87a8x253s1.fsf@kst-u.example.com> (permalink) |
| References | <6a4be947-376c-466e-aa9f-78a6e174725c@googlegroups.com> <mjbai5$u51$1@speranza.aioe.org> <mjbtjr$db3$1@dont-email.me> <87mw12qqk7.fsf@kst-u.example.com> <mjcnfm$43l$1@dont-email.me> |
Richard Heathfield <rjh@cpax.org.uk> writes:
> On 18/05/15 08:43, Keith Thompson wrote:
>> Richard Heathfield <rjh@cpax.org.uk> writes:
>>> On 18/05/15 01:08, Morris Dovey wrote:
>>>> On 5/17/15 12:07 PM, asetofsymbols@gmail.com wrote:
>>>>> Is there any better way?
>>>>
>>>> Of course - look at the declaration!
>>>
>>> Or, for preference, the definition, since this will also tell you
>>> whether the object has actually been defined.
>>>
>>>> If you’re too lazy to do that, you could try (untested)
>>>
>>> If he's too lazy to look at the definition, he's probably too lazy to
>>> do something that takes effort to type and effort to think about.
>>>
>>> OP: look at the definition. Really.
>>
>> How can I portably print the value returned by time(NULL)? Looking at
>> the definition doesn't help.
>
> According to N1570, time() returns a time_t, which is a "real
> type". That means it could be an integer type or a floating point
> type. So the best we can do with time(NULL) in the absence of a time_t
> conversion specifier is to cast to the widest supported floating point
> type, presumably long double. We would do better to use gmtime or
> localtime followed by strftime to get a string in a reliable format,
> and then print that.
Converting a long long to long double can lose information.
The best we can do is this:
#include <stdio.h>
#include <time.h>
#include <stdint.h>
int main(void) {
time_t now = time(NULL);
if ((time_t)-1 > 0) {
// time_t is unsigned
printf("%ju\n", (uintmax_t)now);
}
else if ((time_t)1 / 2 == 0) {
// time_t is signed
printf("%jd\n", (intmax_t)now);
}
else {
// time_t is floating-point
printf("%Lf\n", (long double)now);
}
}
--
Keith Thompson (The_Other_Keith) kst-u@mib.org <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
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determines if it is a signed type asetofsymbols@gmail.com - 2015-05-17 10:07 -0700
Re: determines if it is a signed type Richard Heathfield <rjh@cpax.org.uk> - 2015-05-17 18:12 +0100
Re: determines if it is a signed type asetofsymbols@gmail.com - 2015-05-17 10:34 -0700
Re: determines if it is a signed type asetofsymbols@gmail.com - 2015-05-17 11:09 -0700
Re: determines if it is a signed type Kusalananda <kusalananda@example.com> - 2015-05-17 18:22 +0000
Re: determines if it is a signed type asetofsymbols@gmail.com - 2015-05-17 11:31 -0700
Re: determines if it is a signed type Kusalananda <kusalananda@example.com> - 2015-05-17 19:59 +0000
Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-17 13:12 -0700
Re: determines if it is a signed type Morris Dovey <mrdovey@iedu.com> - 2015-05-17 19:08 -0500
Re: determines if it is a signed type Morris Dovey <mrdovey@iedu.com> - 2015-05-17 19:46 -0500
Re: determines if it is a signed type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-18 01:59 +0100
Re: determines if it is a signed type Morris Dovey <mrdovey@iedu.com> - 2015-05-17 20:10 -0500
Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-18 00:37 -0700
Re: determines if it is a signed type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-18 21:15 +0100
Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-18 15:15 -0700
Re: determines if it is a signed type glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-05-18 21:51 +0000
Re: determines if it is a signed type James Kuyper <jameskuyper@verizon.net> - 2015-05-18 18:00 -0400
Re: determines if it is a signed type glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-05-18 14:37 +0000
Re: determines if it is a signed type jacobnavia <jacob@jacob.remcomp.fr> - 2015-05-18 17:09 +0200
Re: determines if it is a signed type glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-05-18 18:14 +0000
Re: determines if it is a signed type Richard Heathfield <rjh@cpax.org.uk> - 2015-05-18 06:34 +0100
Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-18 00:43 -0700
Re: determines if it is a signed type Richard Heathfield <rjh@cpax.org.uk> - 2015-05-18 13:56 +0100
Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-18 08:00 -0700
Re: determines if it is a signed type Richard Heathfield <rjh@cpax.org.uk> - 2015-05-18 20:35 +0100
Re: determines if it is a signed type jacobnavia <jacob@jacob.remcomp.fr> - 2015-05-18 23:08 +0200
Re: determines if it is a signed type Richard Heathfield <rjh@cpax.org.uk> - 2015-05-18 22:32 +0100
Re: determines if it is a signed type jacobnavia <jacob@jacob.remcomp.fr> - 2015-05-19 00:44 +0200
Re: determines if it is a signed type Richard Heathfield <rjh@cpax.org.uk> - 2015-05-19 00:05 +0100
Re: determines if it is a signed type jacobnavia <jacob@jacob.remcomp.fr> - 2015-05-19 01:43 +0200
Re: determines if it is a signed type Richard Heathfield <rjh@cpax.org.uk> - 2015-05-19 01:08 +0100
Re: determines if it is a signed type "Bartc" <bartc@freeuk.com> - 2015-05-19 11:33 +0100
Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-19 08:15 -0700
Re: determines if it is a signed type "Bartc" <bartc@freeuk.com> - 2015-05-19 19:36 +0100
Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-19 11:55 -0700
Re: determines if it is a signed type jacobnavia <jacob@jacob.remcomp.fr> - 2015-05-19 11:39 +0200
Re: determines if it is a signed type "Bartc" <bartc@freeuk.com> - 2015-05-19 11:44 +0100
Re: determines if it is a signed type jacobnavia <jacob@jacob.remcomp.fr> - 2015-05-19 12:11 +0200
Re: determines if it is a signed type jadill33@gmail.com - 2015-05-19 05:45 -0700
Re: determines if it is a signed type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-19 15:03 +0100
Re: determines if it is a signed type jadill33@gmail.com - 2015-05-19 08:46 -0700
Re: determines if it is a signed type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-19 17:08 +0100
Re: determines if it is a signed type jadill33@gmail.com - 2015-05-19 09:52 -0700
Re: determines if it is a signed type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-19 20:36 +0100
Re: determines if it is a signed type jadill33@gmail.com - 2015-05-20 07:40 -0700
Re: determines if it is a signed type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-20 23:12 +0100
Re: determines if it is a signed type jadill33@gmail.com - 2015-05-21 13:52 -0700
Re: determines if it is a signed type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-21 22:48 +0100
Re: determines if it is a signed type jadill33@gmail.com - 2015-05-22 05:50 -0700
Re: determines if it is a signed type Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-05-22 23:14 +0100
Re: determines if it is a signed type jadill33@gmail.com - 2015-05-26 14:31 -0700
Re: determines if it is a signed type Tim Rentsch <txr@alumni.caltech.edu> - 2015-05-22 23:32 -0700
Re: determines if it is a signed type David Brown <david.brown@hesbynett.no> - 2015-05-20 12:26 +0200
Re: determines if it is a signed type Richard Heathfield <rjh@cpax.org.uk> - 2015-05-19 15:28 +0100
Re: determines if it is a signed type raltbos@xs4all.nl (Richard Bos) - 2015-05-23 10:37 +0000
Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-18 15:21 -0700
Re: determines if it is a signed type Richard Heathfield <rjh@cpax.org.uk> - 2015-05-19 00:04 +0100
Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-19 08:03 -0700
Re: determines if it is a signed type David Brown <david.brown@hesbynett.no> - 2015-05-19 08:47 +0200
Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-19 08:07 -0700
Re: determines if it is a signed type James Kuyper <jameskuyper@verizon.net> - 2015-05-18 11:28 -0400
Re: determines if it is a signed type Keith Thompson <kst-u@mib.org> - 2015-05-18 00:40 -0700
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