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| From | Keith Thompson <kst-u@mib.org> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Pointers, constant values |
| Date | 2015-10-16 12:18 -0700 |
| Organization | None to speak of |
| Message-ID | <ln4mhq62rz.fsf@kst-u.example.com> (permalink) |
| References | <5b2ab074-7644-4798-9b90-a3ae47e1f2b8@googlegroups.com> <ln4mhq7s4z.fsf@kst-u.example.com> <mvr9nb$ra4$1@dont-email.me> <KoaUx.29137$os5.11289@fx14.iad> |
Lew Pitcher <lew.pitcher@digitalfreehold.ca> writes:
> On Friday October 16 2015 12:49, in comp.lang.c, "Bartc" <bc@freeuk.com>
> wrote:
[...]
>> But 'int *array' *is* a pointer to a single element. C allows you to
>> pass a pointer to an actual array, if not the array itself:
>>
>> int array_sum(int (*array)[], int n);
>
> That's one way of looking at it. OTOH, you can also interpret <<array>> above
> as a pointer-to a pointer-to an int. In other words, you haven't really
> passed "a pointer to an actual array", but instead have passed a pointer to a
> pointer (that, hopefully, points to at least one element of an array). Now,
> you have two problems instead of one.
No, `array` is not a pointer to a pointer; it's actually a pointer to an
array. The problem is that the array type is incomplete, so there's not
much you can do with it.
[...]
> I do concur with Keith for the most part, but I differ (slightly) in his
> characterization of the benefit of the "*(pointer+displacement)" argument.
> Where he says:
>> some will argue that using the [] notation is a reminder that it points to
>> an element of an array, not just a single int object.
> I would rephrase that as
> some will argue that using the [] notation is a reminder that it IS INTENDED
> to point to an element of an array, not just a single int object.
> (caps to show the difference in phrasing)
> Hopefully, when using the [] notation, both the caller and the called
> function /agree/ that the parameter is intended to point to an array.
Good point. Using [] notation for a parameter doesn't *enforce*
anything on the caller.
The bottom line, I think, is that array manipulation in C is generally
done via pointers to individual array elements, with other elements
accessed by doing pointer arithmetic. Array indexing is just a
syntactic wrapper around pointer arithmetic (a[i] means *(a+i)).
--
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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Pointers, constant values Alla _ <modelling.data@gmail.com> - 2015-10-16 00:49 -0700
Re: Pointers, constant values Philip Lantz <prl@canterey.us> - 2015-10-16 01:49 -0700
Re: Pointers, constant values James Kuyper <jameskuyper@verizon.net> - 2015-10-16 09:41 -0400
Re: Pointers, constant values supercat@casperkitty.com - 2015-10-16 08:55 -0700
Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-16 08:25 -0700
Re: Pointers, constant values supercat@casperkitty.com - 2015-10-16 09:11 -0700
Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-16 12:06 -0700
Re: Pointers, constant values supercat@casperkitty.com - 2015-10-16 12:55 -0700
Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-16 17:49 +0100
Re: Pointers, constant values Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2015-10-16 13:23 -0400
Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-16 19:34 +0100
Re: Pointers, constant values supercat@casperkitty.com - 2015-10-16 12:05 -0700
Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-16 12:18 -0700
Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-16 12:13 -0700
Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-16 20:33 +0100
Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-16 13:01 -0700
Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-16 21:09 +0100
Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-16 13:41 -0700
Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-16 21:07 +0100
Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-16 21:20 +0100
Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-16 22:02 +0100
Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-16 22:21 +0100
Re: Pointers, constant values supercat@casperkitty.com - 2015-10-16 14:39 -0700
Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-16 15:26 -0700
Re: Pointers, constant values supercat@casperkitty.com - 2015-10-16 15:44 -0700
Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-16 16:58 -0700
Re: Pointers, constant values supercat@casperkitty.com - 2015-10-16 17:28 -0700
Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-16 22:50 +0100
Re: Pointers, constant values supercat@casperkitty.com - 2015-10-16 15:14 -0700
Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-17 01:23 +0100
Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-17 19:39 +0100
Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-17 22:42 +0100
Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-18 00:31 +0100
Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-18 02:11 +0100
Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-18 11:59 +0100
Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-18 12:12 +0100
Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-18 12:28 +0100
Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-18 23:16 +0100
Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-18 23:34 +0100
Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-19 01:45 +0100
Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-19 11:51 +0100
Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-19 12:55 +0100
Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-19 13:51 +0100
Re: Pointers, constant values Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-19 06:02 -0700
Re: Pointers, constant values supercat@casperkitty.com - 2015-10-19 07:02 -0700
Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-19 15:39 +0100
Re: Pointers, constant values supercat@casperkitty.com - 2015-10-19 08:54 -0700
Re: Pointers, constant values Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-19 09:14 -0700
Re: Pointers, constant values supercat@casperkitty.com - 2015-10-19 10:21 -0700
Re: Pointers, constant values Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-19 12:57 -0700
Re: Pointers, constant values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-19 21:20 +0000
Re: Pointers, constant values supercat@casperkitty.com - 2015-10-20 20:50 -0700
Re: Pointers, constant values glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-21 04:58 +0000
Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-19 08:40 -0700
Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-19 20:17 +0100
Re: Pointers, constant values supercat@casperkitty.com - 2015-10-17 16:44 -0700
Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-18 11:52 +0100
Re: Pointers, constant values Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-18 05:15 -0700
Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-18 21:54 +0100
Re: Pointers, constant values Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-10-18 16:09 -0700
Re: Pointers, constant values supercat@casperkitty.com - 2015-10-18 07:55 -0700
Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-18 21:47 +0100
Re: Pointers, constant values supercat@casperkitty.com - 2015-10-18 15:37 -0700
Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-19 00:10 +0100
Re: Pointers, constant values supercat@casperkitty.com - 2015-10-18 19:04 -0700
Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-16 21:13 +0100
Re: Pointers, constant values Ian Collins <ian-news@hotmail.com> - 2015-10-17 11:27 +1300
Re: Pointers, constant values Bartc <bc@freeuk.com> - 2015-10-17 00:56 +0100
Re: Pointers, constant values Les Cargill <lcargill99@comcast.com> - 2015-10-16 12:37 -0500
Re: Pointers, constant values James Kuyper <jameskuyper@verizon.net> - 2015-10-16 14:22 -0400
Re: Pointers, constant values Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-10-16 18:57 +0000
Re: Pointers, constant values Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-16 20:40 +0100
Re: Pointers, constant values Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-10-16 20:46 +0000
Re: Pointers, constant values Keith Thompson <kst-u@mib.org> - 2015-10-16 14:24 -0700
Re: Pointers, constant values Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-10-19 12:43 +0000
Re: Pointers, constant values Siri Cruz <chine.bleu@yahoo.com> - 2015-10-16 13:20 -0700
Re: Pointers, constant values supercat@casperkitty.com - 2015-10-17 13:59 -0700
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