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Re: Fortran Guy Learning C - Structures...

From Richard Heathfield <rjh@cpax.org.uk>
Newsgroups comp.lang.c
Subject Re: Fortran Guy Learning C - Structures...
Date 2015-02-08 22:04 +0000
Organization go, ion artisan!
Message-ID <mb8mgf$8ef$1@dont-email.me> (permalink)
References (11 earlier) <mb7hab$90b$1@dont-email.me> <ln7fvsjjzl.fsf@nuthaus.mib.org> <mb8fa5$9og$1@dont-email.me> <mb8fjl$atg$1@dont-email.me> <lnr3u0hz0k.fsf@nuthaus.mib.org>

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On 08/02/15 21:30, Keith Thompson wrote:
> Richard Heathfield <rjh@cpax.org.uk> writes:
>> On 08/02/15 20:01, Bartc wrote:
>>> On 08/02/2015 19:12, Keith Thompson wrote:
>> <snip>
>>>>
>>>> Look at this piece of code:
>>>>
>>>>      x = y + z;
>>>>
>>>> Any of x, y, and z could be either an integer or a floating-point
>>>> object.  In some languages, including C, they could be certain
>>>> combinations of integers and pointers.
>>>
>>> Sure, but in the absence of any "*" prefix operators, you know there is
>>> no pointer dereferencing going on. Not so with array indexing.
>>>
>>> With a[i][j], is that a direct, rectangular array,
>>
>> No such thing in C, unless you mean a rather long, very thin rectangle.
>>
>> a[i][j] means *(a[i] + j), which means *( *(a + i) + j)
>>
>> so you know for sure that there is some pointer dereferencing going on.
>>
>> <snip>
>
> Yes, but `a` could be defined as a 2-dimensional array (i.e., an array
> of arrays):
>
>      int a[10][10];
>      int i = 5;
>      int j = 5;
>      a[i][j] = 42;
>
> The [] operator is defined to operate on a pointer (which must point to
> an array element), and in this case there are two levels of an array
> expression decaying to a pointer and being dereferenced.  But Bartc is
> correct in saying that given `a[i][j]`, `a` could have been defined as
> an array of arrays (which can reasonably be called a rectangular array).


We're tilting at windmills. As we both know and as you rightly say, an 
array in C is defined in terms of pointers (6.5.2.1). It is therefore 
necessarily true that an array of arrays is also ultimately defined in 
terms of pointers, and accessing an array element is isomorphic to 
dereferencing a pointer.

-- 
Richard Heathfield
Email: rjh at cpax dot org dot uk
"Usenet is a strange place" - dmr 29 July 1999
Sig line 4 vacant - apply within

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Thread

Fortran Guy Learning C - Structures... jeffkrob16@gmail.com - 2015-02-03 09:33 -0800
  Re: Fortran Guy Learning C - Structures... Bartc <bc@freeuk.com> - 2015-02-03 17:59 +0000
  Re: Fortran Guy Learning C - Structures... James Kuyper <jameskuyper@verizon.net> - 2015-02-03 13:01 -0500
  Re: Fortran Guy Learning C - Structures... Barry Schwarz <schwarzb@dqel.com> - 2015-02-03 10:49 -0800
  Re: Fortran Guy Learning C - Structures... Richard Heathfield <invalid@see.sig.invalid> - 2015-02-03 18:54 +0000
  Fortran Guy Learning C - Structures... asetofsymbols@gmail.com - 2015-02-03 11:50 -0800
    Fortran Guy Learning C - Structures... asetofsymbols@gmail.com - 2015-02-03 12:07 -0800
    Re: Fortran Guy Learning C - Structures... Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2015-02-03 15:14 -0500
    Re: Fortran Guy Learning C - Structures... Barry Schwarz <schwarzb@dqel.com> - 2015-02-03 15:06 -0800
      Re: Fortran Guy Learning C - Structures... asetofsymbols@gmail.com - 2015-02-03 22:19 -0800
  Re: Fortran Guy Learning C - Structures... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-02-03 21:40 +0000
    Re: Fortran Guy Learning C - Structures... asetofsymbols@gmail.com - 2015-02-03 22:56 -0800
      Re: Fortran Guy Learning C - Structures... asetofsymbols@gmail.com - 2015-02-03 23:02 -0800
      Re: Fortran Guy Learning C - Structures... asetofsymbols@gmail.com - 2015-02-04 00:01 -0800
  Re: Fortran Guy Learning C - Structures... jeffkrob16@gmail.com - 2015-02-04 10:53 -0800
    Re: Fortran Guy Learning C - Structures... Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-02-04 11:21 -0800
    Re: Fortran Guy Learning C - Structures... Bartc <bc@freeuk.com> - 2015-02-04 19:32 +0000
    Re: Fortran Guy Learning C - Structures... Barry Schwarz <schwarzb@dqel.com> - 2015-02-04 11:59 -0800
    Re: Fortran Guy Learning C - Structures... hormelfree@gmail.com - 2015-02-04 15:30 -0800
      Re: Fortran Guy Learning C - Structures... jeffkrob16@gmail.com - 2015-02-04 19:41 -0800
        Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-05 04:06 +0000
          Re: Fortran Guy Learning C - Structures... Bartc <bc@freeuk.com> - 2015-02-05 10:36 +0000
            Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-05 10:59 +0000
            Re: Fortran Guy Learning C - Structures... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-02-05 11:03 +0000
            Re: Fortran Guy Learning C - Structures... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-02-05 12:30 +0000
              Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-05 12:46 +0000
                Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-05 12:49 +0000
            Re: Fortran Guy Learning C - Structures... hormelfree@gmail.com - 2015-02-05 15:08 -0800
          Re: Fortran Guy Learning C - Structures... Keith Thompson <kst-u@mib.org> - 2015-02-05 08:48 -0800
          Re: Fortran Guy Learning C - Structures... hormelfree@gmail.com - 2015-02-05 15:16 -0800
            Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-05 23:35 +0000
              Re: Fortran Guy Learning C - Structures... hormelfree@gmail.com - 2015-02-07 12:11 -0800
                Re: Fortran Guy Learning C - Structures... Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-02-07 12:22 -0800
                Re: Fortran Guy Learning C - Structures... Bartc <bc@freeuk.com> - 2015-02-07 22:03 +0000
                Re: Fortran Guy Learning C - Structures... Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-02-07 14:47 -0800
                Re: Fortran Guy Learning C - Structures... Keith Thompson <kst-u@mib.org> - 2015-02-07 17:15 -0800
                Re: Fortran Guy Learning C - Structures... Ian Collins <ian-news@hotmail.com> - 2015-02-08 17:22 +1300
                Re: Fortran Guy Learning C - Structures... Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-02-08 02:47 -0800
                Re: Fortran Guy Learning C - Structures... Keith Thompson <kst-u@mib.org> - 2015-02-08 11:20 -0800
                Re: Fortran Guy Learning C - Structures... Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-02-08 14:36 -0800
                Re: Fortran Guy Learning C - Structures... Ian Collins <ian-news@hotmail.com> - 2015-02-09 11:51 +1300
                Re: Fortran Guy Learning C - Structures... Keith Thompson <kst-u@mib.org> - 2015-02-08 15:02 -0800
                Re: Fortran Guy Learning C - Structures... Geoff <geoff@invalid.invalid> - 2015-02-08 16:55 -0800
                Re: Fortran Guy Learning C - Structures... Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-02-09 03:24 -0800
                Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-09 11:56 +0000
                Re: Fortran Guy Learning C - Structures... David Brown <david.brown@hesbynett.no> - 2015-02-09 14:25 +0100
                Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-09 14:00 +0000
                Re: Fortran Guy Learning C - Structures... David Brown <david.brown@hesbynett.no> - 2015-02-09 15:26 +0100
                Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-09 14:39 +0000
                Re: Fortran Guy Learning C - Structures... David Brown <david.brown@hesbynett.no> - 2015-02-09 16:59 +0100
                Re: Fortran Guy Learning C - Structures... raltbos@xs4all.nl (Richard Bos) - 2015-02-09 16:01 +0000
                Re: Fortran Guy Learning C - Structures... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-02-09 13:39 +0000
                Re: Fortran Guy Learning C - Structures... James Kuyper <jameskuyper@verizon.net> - 2015-02-09 09:46 -0500
                Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-09 14:50 +0000
                Re: Fortran Guy Learning C - Structures... Keith Thompson <kst-u@mib.org> - 2015-02-09 08:22 -0800
                Re: Fortran Guy Learning C - Structures... gazelle@shell.xmission.com (Kenny McCormack) - 2015-02-09 13:24 +0000
                Re: Fortran Guy Learning C - Structures... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-02-09 16:03 +0000
                Re: Fortran Guy Learning C - Structures... Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-02-09 11:01 -0800
                Re: Fortran Guy Learning C - Structures... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-02-09 21:54 +0000
                Re: Fortran Guy Learning C - Structures... Öö Tiib <ootiib@hot.ee> - 2015-02-09 19:22 -0800
                Re: Fortran Guy Learning C - Structures... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-02-10 11:34 +0000
                Re: Fortran Guy Learning C - Structures... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-02-10 14:15 +0000
                Re: Fortran Guy Learning C - Structures... Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-02-10 00:38 -0800
                Re: Fortran Guy Learning C - Structures... Bartc <bc@freeuk.com> - 2015-02-10 09:21 +0000
                Re: Fortran Guy Learning C - Structures... Ian Collins <ian-news@hotmail.com> - 2015-02-10 22:24 +1300
                Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-10 09:25 +0000
                Re: Fortran Guy Learning C - Structures... Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-02-10 09:03 -0800
                Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-10 17:12 +0000
                Re: Fortran Guy Learning C - Structures... Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-02-10 09:56 -0800
                Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-10 18:12 +0000
                Re: Fortran Guy Learning C - Structures... Keith Thompson <kst-u@mib.org> - 2015-02-10 11:24 -0800
                Re: Fortran Guy Learning C - Structures... gazelle@shell.xmission.com (Kenny McCormack) - 2015-02-10 20:18 +0000
                Re: Fortran Guy Learning C - Structures... Keith Thompson <kst-u@mib.org> - 2015-02-10 09:16 -0800
                Re: Fortran Guy Learning C - Structures... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-02-10 22:12 +0000
                Re: Fortran Guy Learning C - Structures... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-02-11 02:58 +0000
                Re: Fortran Guy Learning C - Structures... Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-02-10 19:00 -0800
                Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-11 07:56 +0000
                Re: Fortran Guy Learning C - Structures... David Thompson <dave.thompson2@verizon.net> - 2015-02-22 18:08 -0500
                Re: Fortran Guy Learning C - Structures... Keith Thompson <kst-u@mib.org> - 2015-02-10 16:01 -0800
                Re: Fortran Guy Learning C - Structures... Ian Collins <ian-news@hotmail.com> - 2015-02-10 11:26 +1300
                Re: Fortran Guy Learning C - Structures... David Brown <david.brown@hesbynett.no> - 2015-02-10 10:29 +0100
                Re: Fortran Guy Learning C - Structures... Keith Thompson <kst-u@mib.org> - 2015-02-09 08:32 -0800
                Re: Fortran Guy Learning C - Structures... Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-02-09 11:09 -0800
                Re: Fortran Guy Learning C - Structures... gazelle@shell.xmission.com (Kenny McCormack) - 2015-02-09 19:39 +0000
                Re: Fortran Guy Learning C - Structures... Martin Shobe <martin.shobe@yahoo.com> - 2015-02-09 14:04 -0600
                Re: Fortran Guy Learning C - Structures... Keith Thompson <kst-u@mib.org> - 2015-02-09 12:24 -0800
                Re: Fortran Guy Learning C - Structures... David Brown <david.brown@hesbynett.no> - 2015-02-10 10:34 +0100
                Re: Fortran Guy Learning C - Structures... Bartc <bc@freeuk.com> - 2015-02-08 11:42 +0000
                Re: Fortran Guy Learning C - Structures... Bartc <bc@freeuk.com> - 2015-02-07 22:50 +0000
                Re: Fortran Guy Learning C - Structures... Keith Thompson <kst-u@mib.org> - 2015-02-07 17:07 -0800
                Re: Fortran Guy Learning C - Structures... Bartc <bc@freeuk.com> - 2015-02-08 11:29 +0000
                Re: Fortran Guy Learning C - Structures... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-02-08 12:14 +0000
                Re: Fortran Guy Learning C - Structures... Bartc <bc@freeuk.com> - 2015-02-08 13:44 +0000
                Re: Fortran Guy Learning C - Structures... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-02-08 22:39 +0000
                Re: Fortran Guy Learning C - Structures... Keith Thompson <kst-u@mib.org> - 2015-02-08 11:12 -0800
                Re: Fortran Guy Learning C - Structures... Bartc <bc@freeuk.com> - 2015-02-08 20:01 +0000
                Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-08 20:06 +0000
                Re: Fortran Guy Learning C - Structures... Bartc <bc@freeuk.com> - 2015-02-08 21:04 +0000
                Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-08 21:11 +0000
                Re: Fortran Guy Learning C - Structures... Bartc <bc@freeuk.com> - 2015-02-08 23:48 +0000
                Re: Fortran Guy Learning C - Structures... Keith Thompson <kst-u@mib.org> - 2015-02-08 13:30 -0800
                Re: Fortran Guy Learning C - Structures... Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2015-02-08 16:47 -0500
                Re: Fortran Guy Learning C - Structures... Keith Thompson <kst-u@mib.org> - 2015-02-08 14:53 -0800
                Re: Fortran Guy Learning C - Structures... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-02-09 02:31 +0000
                Re: Fortran Guy Learning C - Structures... Bartc <bc@freeuk.com> - 2015-02-09 10:35 +0000
                Re: Fortran Guy Learning C - Structures... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-02-09 13:57 +0000
                Re: Fortran Guy Learning C - Structures... Keith Thompson <kst-u@mib.org> - 2015-02-09 07:59 -0800
                Re: Fortran Guy Learning C - Structures... Öö Tiib <ootiib@hot.ee> - 2015-02-09 18:15 -0800
                Re: Fortran Guy Learning C - Structures... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-02-10 05:54 +0000
                Re: Fortran Guy Learning C - Structures... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-02-09 16:17 +0000
                Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-08 22:04 +0000
                Re: Fortran Guy Learning C - Structures... Keith Thompson <kst-u@mib.org> - 2015-02-08 14:57 -0800
                Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-08 23:45 +0000
                Re: Fortran Guy Learning C - Structures... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-02-09 02:53 +0000
                Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-09 09:29 +0000
                Re: Fortran Guy Learning C - Structures... Bartc <bc@freeuk.com> - 2015-02-09 10:10 +0000
                Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-09 11:24 +0000
                Re: Fortran Guy Learning C - Structures... Ike Naar <ike@iceland.freeshell.org> - 2015-02-09 17:36 +0000
                Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-09 17:56 +0000
                Re: Fortran Guy Learning C - Structures... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-02-09 10:51 +0000
                Re: Fortran Guy Learning C - Structures... Bartc <bc@freeuk.com> - 2015-02-09 11:10 +0000
                Re: Fortran Guy Learning C - Structures... Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-02-09 11:25 +0000
                Re: Fortran Guy Learning C - Structures... Bartc <bc@freeuk.com> - 2015-02-09 11:43 +0000
                Re: Fortran Guy Learning C - Structures... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-02-10 02:13 +0000
                Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-10 03:26 +0000
                Re: Fortran Guy Learning C - Structures... raltbos@xs4all.nl (Richard Bos) - 2015-02-09 21:18 +0000
                Re: Fortran Guy Learning C - Structures... Bartc <bc@freeuk.com> - 2015-02-09 23:11 +0000
                Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-08 12:10 +0000
                Re: Fortran Guy Learning C - Structures... Keith Thompson <kst-u@mib.org> - 2015-02-08 11:18 -0800
                Re: Fortran Guy Learning C - Structures... Richard Heathfield <rjh@cpax.org.uk> - 2015-02-08 19:27 +0000
                Re: Fortran Guy Learning C - Structures... hormelfree@gmail.com - 2015-02-09 15:00 -0800
                Re: Fortran Guy Learning C - Structures... Keith Thompson <kst-u@mib.org> - 2015-02-09 16:00 -0800
        Re: Fortran Guy Learning C - Structures... Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-02-05 02:49 -0800
          Re: Fortran Guy Learning C - Structures... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-02-05 11:16 +0000
          Re: Fortran Guy Learning C - Structures... Keith Thompson <kst-u@mib.org> - 2015-02-05 09:00 -0800
            Re: Fortran Guy Learning C - Structures... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-02-06 00:29 +0000
              Re: Fortran Guy Learning C - Structures... Robert Wessel <robertwessel2@yahoo.com> - 2015-02-05 19:20 -0600
              Re: Fortran Guy Learning C - Structures... "Charles Richmond" <numerist@aquaporin4.com> - 2015-02-06 16:15 -0600
                Re: Fortran Guy Learning C - Structures... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-02-07 00:57 +0000
              Re: Fortran Guy Learning C - Structures... Kaz Kylheku <kaz@kylheku.com> - 2015-02-07 01:40 +0000
                Re: Fortran Guy Learning C - Structures... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-02-07 08:22 +0000
                Re: Fortran Guy Learning C - Structures... glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-02-07 12:06 +0000
            Re: Fortran Guy Learning C - Structures... John Bode <jfbode1029@gmail.com> - 2015-02-06 15:03 -0800
        Re: Fortran Guy Learning C - Structures... hormelfree@gmail.com - 2015-02-05 15:12 -0800

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