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Groups > comp.lang.c > #138945
| Subject | Re: A final word on casting. |
|---|---|
| Newsgroups | comp.lang.c |
| References | <af569436-b2e1-492b-8379-9f927013c590@googlegroups.com> |
| From | Bart <bc@freeuk.com> |
| Message-ID | <1YKTD.30400$CD3.15082@fx05.am4> (permalink) |
| Organization | virginmedia.com |
| Date | 2018-12-23 12:11 +0000 |
On 23/12/2018 11:02, chanrasjid@gmail.com wrote:
> I have been playing with C for about 30 years, but I could never get to really understand casting. I made various weak attempts and gave up; I knew I don't need to be professional in C.
>
> I take my layman approach to casting: it is to represent the value of a certain type in a different data type.
>
> Some things I tested work and I don't care about its correctness. I always get it correct: (int) 1.23 always give 1.
Try:
printf("%d\n", (int)1.9999999999999999999999999999999);
I seem to get the answer 2.
> Casting a signed int to a long unsigned integer is meaningless if the original integer is negative; I think the experts know what result would be returned as per some C standards; but then what is the purpose when it is meaningless.
It seems to be the same as (unsigned long long)(signed long long int)(a)
when a is signed int. So, sign-extend a to the new width, then interpret
the bits as unsigned.
> The only use I think is safe is casting compatible types to another with the larger storage, as int to _int64, or float to double. Casting double to float is OK as we expect a loss of precision.
Double has a wider magnitude range than float, so it can fail that way
(the float value ends up as infinity when the magnitude is too big).
--
bart
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A final word on casting. chanrasjid@gmail.com - 2018-12-23 03:02 -0800
Re: A final word on casting. Bart <bc@freeuk.com> - 2018-12-23 12:11 +0000
Re: A final word on casting. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-23 13:08 +0000
Re: A final word on casting. Bart <bc@freeuk.com> - 2018-12-23 14:43 +0000
Re: A final word on casting. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-23 14:56 +0000
Re: A final word on casting. chanrasjid@gmail.com - 2018-12-23 07:08 -0800
Re: A final word on casting. Bart <bc@freeuk.com> - 2018-12-23 15:55 +0000
Re: A final word on casting. Bart <bc@freeuk.com> - 2018-12-23 16:07 +0000
Re: A final word on casting. James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-23 08:21 -0800
Re: A final word on casting. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-23 17:56 +0000
Re: A final word on casting. Bart <bc@freeuk.com> - 2018-12-23 19:23 +0000
Re: A final word on casting. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-23 20:12 +0000
Re: A final word on casting. James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-23 14:06 -0800
Re: A final word on casting. Tim Rentsch <txr@alumni.caltech.edu> - 2018-12-28 09:34 -0800
Re: A final word on casting. Bart <bc@freeuk.com> - 2018-12-28 20:29 +0000
Re: A final word on casting. Tim Rentsch <txr@alumni.caltech.edu> - 2018-12-28 15:07 -0800
Re: A final word on casting. Richard Damon <Richard@Damon-Family.org> - 2018-12-28 20:56 -0500
Re: A final word on casting. Tim Rentsch <txr@alumni.caltech.edu> - 2018-12-29 09:22 -0800
Re: A final word on casting. Tim Rentsch <txr@alumni.caltech.edu> - 2019-01-01 13:27 -0800
Re: A final word on casting. Bart <bc@freeuk.com> - 2019-01-02 01:07 +0000
Re: A final word on casting. Bart <bc@freeuk.com> - 2019-01-03 18:55 +0000
Re: A final word on casting. Richard Damon <Richard@Damon-Family.org> - 2019-01-03 22:27 -0500
Re: A final word on casting. James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-01-04 16:25 -0500
Re: A final word on casting. Ike Naar <ike@iceland.freeshell.org> - 2018-12-28 19:10 +0000
Re: A final word on casting. James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-28 12:33 -0800
Re: A final word on casting. "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-23 14:11 -0800
Re: A final word on casting. Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2018-12-24 02:54 -0800
Re: A final word on casting. fir <profesor.fir@gmail.com> - 2018-12-24 03:24 -0800
Re: A final word on casting. fir <profesor.fir@gmail.com> - 2018-12-24 03:29 -0800
Re: A final word on casting. fir <profesor.fir@gmail.com> - 2018-12-24 03:45 -0800
Re: A final word on casting. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-24 13:44 +0000
Re: A final word on casting. Richard Damon <Richard@Damon-Family.org> - 2018-12-24 08:51 -0500
Re: A final word on casting. Richard Damon <Richard@Damon-Family.org> - 2018-12-23 14:53 -0500
Re: A final word on casting. Robert Wessel <robertwessel2@yahoo.com> - 2018-12-24 09:39 -0600
Re: A final word on casting. Richard Damon <Richard@Damon-Family.org> - 2018-12-24 13:38 -0500
Re: A final word on casting. Manfred <noname@add.invalid> - 2018-12-23 21:22 +0100
Re: A final word on casting. Manfred <noname@add.invalid> - 2018-12-23 21:33 +0100
Re: A final word on casting. James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-23 10:56 -0500
Re: A final word on casting. Sjouke Burry <burrynulnulfour@ppllaanneett.nnll> - 2018-12-23 17:18 +0100
Re: A final word on casting. Bart <bc@freeuk.com> - 2018-12-23 20:03 +0000
Re: A final word on casting. "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-28 14:47 -0500
Re: A final word on casting. Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-23 12:24 +0000
Re: A final word on casting. Richard Damon <Richard@Damon-Family.org> - 2018-12-23 07:28 -0500
Re: A final word on casting. Tim Rentsch <txr@alumni.caltech.edu> - 2018-12-28 07:50 -0800
Re: A final word on casting. fir <profesor.fir@gmail.com> - 2018-12-23 04:35 -0800
Re: A final word on casting. fir <profesor.fir@gmail.com> - 2018-12-23 04:42 -0800
Re: A final word on casting. fir <profesor.fir@gmail.com> - 2018-12-23 04:52 -0800
Re: A final word on casting. James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-23 10:28 -0500
Re: A final word on casting. Barry Schwarz <schwarzb@dqel.com> - 2018-12-23 11:39 -0800
Re: A final word on casting. Ike Naar <ike@iceland.freeshell.org> - 2018-12-24 07:56 +0000
Re: A final word on casting. chanrasjid@gmail.com - 2018-12-24 14:03 -0800
Re: A final word on casting. Barry Schwarz <schwarzb@dqel.com> - 2018-12-24 14:39 -0800
Re: A final word on casting. chanrasjid@gmail.com - 2018-12-24 14:50 -0800
Re: A final word on casting. Keith Thompson <kst-u@mib.org> - 2018-12-24 15:34 -0800
Re: A final word on casting. Keith Thompson <kst-u@mib.org> - 2018-12-24 15:23 -0800
Re: A final word on casting. chanrasjid@gmail.com - 2018-12-24 20:34 -0800
Re: A final word on casting. Keith Thompson <kst-u@mib.org> - 2018-12-24 14:52 -0800
Re: A final word on casting. chanrasjid@gmail.com - 2018-12-24 20:25 -0800
Re: A final word on casting. James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-24 17:52 -0500
Re: A final word on casting. luser droog <luser.droog@gmail.com> - 2018-12-24 21:27 -0800
Re: A final word on casting. luser droog <luser.droog@gmail.com> - 2018-12-24 21:39 -0800
Re: A final word on casting. chanrasjid@gmail.com - 2018-12-24 22:36 -0800
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