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Groups > comp.lang.c++ > #72021
| From | Tim Rentsch <tr.17687@z991.linuxsc.com> |
|---|---|
| Newsgroups | comp.lang.c++ |
| Subject | Re: two's complement idea |
| Date | 2020-02-25 07:56 -0800 |
| Organization | A noiseless patient Spider |
| Message-ID | <86y2sqace9.fsf@linuxsc.com> (permalink) |
| References | <qppva0$cbj$1@news.albasani.net> <r08tpr$e3b$1@news.albasani.net> <r090qk$dv2$1@dont-email.me> <r2veum$8oa$1@reader2.panix.com> |
cross@spitfire.i.gajendra.net (Dan Cross) writes: > In article <r090qk$dv2$1@dont-email.me>, > Alf P. Steinbach <alf.p.steinbach+usenet@gmail.com> wrote: > >> On 22.01.2020 08:32, Bonita Montero wrote: >> >>> I recently had the problem that I wanted to have a constant which is >>> size_t wide and where the highest bit is set. I simply solved it that >>> way (I assume ptrdiff_t as wide as size_t, but this should be common >>> today on all platforms): >>> std::size_t const SIZE_T_MSB = std::numeric_limits<ptrdiff_t>::min(); >>> A guarantee from the standard that signed values are 2's-complement >>> woud be nice for that. >> >> C++20 will give you that guarantee. >> >> But e.g. `size_t(-1) - size_t(-1)/2` does the job with just C++98 >> guarantees. > > Hmm, can't one simply compute: > > ~(size_t)0 ^ (~(size_t)0 >> 1) > > ? Why not just this? (size_t)-1 /2 +1
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Re: two's complement idea Bonita Montero <Bonita.Montero@gmail.com> - 2020-01-22 08:32 +0100
Re: two's complement idea "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2020-01-22 09:23 +0100
Re: two's complement idea Bonita Montero <Bonita.Montero@gmail.com> - 2020-01-22 14:20 +0100
Re: two's complement idea Chris Vine <chris@cvine--nospam--.freeserve.co.uk> - 2020-01-22 13:37 +0000
Re: two's complement idea Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-01-27 01:17 -0800
Re: two's complement idea "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2020-01-27 12:35 +0100
Re: two's complement idea Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-02-15 05:56 -0800
Re: two's complement idea "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2020-02-16 09:17 +0100
Re: two's complement idea Richard Damon <Richard@Damon-Family.org> - 2020-02-21 19:35 -0500
Re: two's complement idea "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2020-02-22 07:01 +0100
Re: two's complement idea Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-02-24 08:22 -0800
Re: two's complement idea cross@spitfire.i.gajendra.net (Dan Cross) - 2020-02-24 03:12 +0000
Re: two's complement idea cdalten@gmail.com - 2020-02-24 05:53 -0800
Re: two's complement idea Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-02-25 07:56 -0800
Re: two's complement idea cross@spitfire.i.gajendra.net (Dan Cross) - 2020-02-25 22:00 +0000
Re: two's complement idea Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-02-25 16:14 -0800
Re: two's complement idea cdalten@gmail.com - 2020-02-25 18:18 -0800
Re: two's complement idea cross@spitfire.i.gajendra.net (Dan Cross) - 2020-02-26 02:22 +0000
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