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Groups > comp.lang.c > #164418
| From | Meredith Montgomery <mmontgomery@levado.to> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: does a double cast to unsigned makes sense in any circumstance? |
| Date | 2022-01-15 22:09 -0300 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <86h7a4trk3.fsf@levado.to> (permalink) |
| References | <86czl8kaew.fsf@levado.to> <sqvc03$v6n$1@dont-email.me> |
Bart <bc@freeuk.com> writes:
> On 03/01/2022 17:15, Meredith Montgomery wrote:
>> I've seen this somewhere or I wrote this some time in the past for some
>> reason and I can't see how this make sense any longer. In a procedure
>> to read a numeric string and turn it into a number, we need to convert
>> each char-digit to some kind of integer:
>> (uint64_t) (unsigned char) (s[pos] - '0');
>> But the double cast here seems odd. I could have written this by
>> copying it from somewhere else. Today, what I would write is just
>> (uint64_t) (s[pos] - '0');
>> Am I making a mistake now? I can't anything wrong with this. Isn't
>> a
>> char just an int? I'm turning an int into an unsigned integer (of a
>> larger size).
>
> Have you tried it? With this code:
>
> signed char c=-10;
> printf("%llu\n", (unsigned long long) c);
> printf("%llu\n", (unsigned long long) (unsigned char) c);
>
> The output is
>
> 18446744073709551606
> 246
>
> So clearly there's a difference.
Indeed. Thank you. I had tried it, but I wasn't quite thinking of
negative numbers because I was thinking of just my chars and my chars
are never negative. So the purpose there is to not let the number grow
to 64 bits. That's my understanding right now. Thank you.
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does a double cast to unsigned makes sense in any circumstance? Meredith Montgomery <mmontgomery@levado.to> - 2022-01-03 14:15 -0300
Re: does a double cast to unsigned makes sense in any circumstance? Bart <bc@freeuk.com> - 2022-01-03 17:32 +0000
Re: does a double cast to unsigned makes sense in any circumstance? Meredith Montgomery <mmontgomery@levado.to> - 2022-01-15 22:09 -0300
Re: does a double cast to unsigned makes sense in any circumstance? Andrey Tarasevich <andreytarasevich@hotmail.com> - 2022-01-03 10:06 -0800
Re: does a double cast to unsigned makes sense in any circumstance? Meredith Montgomery <mmontgomery@levado.to> - 2022-01-15 22:12 -0300
Re: does a double cast to unsigned makes sense in any circumstance? James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-15 23:12 -0500
Re: does a double cast to unsigned makes sense in any circumstance? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-20 19:37 -0800
Re: does a double cast to unsigned makes sense in any circumstance? "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2022-01-21 09:35 -0800
Re: does a double cast to unsigned makes sense in any circumstance? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-21 17:19 -0800
Re: does a double cast to unsigned makes sense in any circumstance? Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-03 19:31 +0100
Re: does a double cast to unsigned makes sense in any circumstance? Meredith Montgomery <mmontgomery@levado.to> - 2022-01-15 22:14 -0300
Re: does a double cast to unsigned makes sense in any circumstance? James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-15 23:24 -0500
Re: does a double cast to unsigned makes sense in any circumstance? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-01-16 13:30 -0800
Re: does a double cast to unsigned makes sense in any circumstance? James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-16 23:25 -0500
Re: does a double cast to unsigned makes sense in any circumstance? Meredith Montgomery <mmontgomery@levado.to> - 2022-01-17 09:43 -0300
Re: does a double cast to unsigned makes sense in any circumstance? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-01-17 13:59 -0800
Re: does a double cast to unsigned makes sense in any circumstance? Meredith Montgomery <mmontgomery@levado.to> - 2022-01-28 22:13 -0300
Re: does a double cast to unsigned makes sense in any circumstance? James Kuyper <jameskuyper@alumni.caltech.edu> - 2022-01-28 21:29 -0500
Re: does a double cast to unsigned makes sense in any circumstance? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-02-03 22:28 -0800
Re: does a double cast to unsigned makes sense in any circumstance? "james...@alumni.caltech.edu" <jameskuyper@alumni.caltech.edu> - 2022-02-04 10:43 -0800
Re: does a double cast to unsigned makes sense in any circumstance? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-01-28 19:37 -0800
Re: does a double cast to unsigned makes sense in any circumstance? Manfred <noname@add.invalid> - 2022-01-30 03:45 +0100
Re: does a double cast to unsigned makes sense in any circumstance? Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2022-01-30 00:01 -0800
Re: does a double cast to unsigned makes sense in any circumstance? Richard Damon <Richard@Damon-Family.org> - 2022-01-30 12:59 -0500
Re: does a double cast to unsigned makes sense in any circumstance? Meredith Montgomery <mmontgomery@levado.to> - 2022-01-17 09:41 -0300
Re: does a double cast to unsigned makes sense in any circumstance? Richard Damon <Richard@Damon-Family.org> - 2022-01-03 14:37 -0500
Re: does a double cast to unsigned makes sense in any circumstance? Meredith Montgomery <mmontgomery@levado.to> - 2022-01-15 22:15 -0300
Re: does a double cast to unsigned makes sense in any circumstance? Richard Damon <Richard@Damon-Family.org> - 2022-01-15 20:55 -0500
Re: does a double cast to unsigned makes sense in any circumstance? Meredith Montgomery <mmontgomery@levado.to> - 2022-01-17 09:44 -0300
Re: does a double cast to unsigned makes sense in any circumstance? Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-16 05:13 +0100
Re: does a double cast to unsigned makes sense in any circumstance? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-15 18:53 -0800
Re: does a double cast to unsigned makes sense in any circumstance? Meredith Montgomery <mmontgomery@levado.to> - 2022-01-17 09:46 -0300
Re: does a double cast to unsigned makes sense in any circumstance? Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-29 16:57 +0100
Re: does a double cast to unsigned makes sense in any circumstance? Öö Tiib <ootiib@hot.ee> - 2022-01-29 09:54 -0800
Re: does a double cast to unsigned makes sense in any circumstance? Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-30 13:17 +0100
Re: does a double cast to unsigned makes sense in any circumstance? Öö Tiib <ootiib@hot.ee> - 2022-01-30 23:53 -0800
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