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Re: just a curiosity about starting array indexing at 0 as opposed to 1

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Lew Pitcher <lew.pitcher@digitalfreehold.ca> wrote:
> On Saturday November 21 2015 21:50, in comp.lang.c, "G G" <gdotone@gmail.com>
> wrote:
 
>> Just a curiosity about C starting array subscripts at 0 as
>> opposed to starting at 1.
 
(snip)

> It is implicit in the structure of arrays.
 
> K&R "The C Programming Language", Chapter 5 "Pointers and Arrays"
> 
>  "Rather more surprising, at least at first sight, is the fact that a
>   reference to a[i] can also be written as *(a+i). In evaluating a[i], C
>   converts it to *(a+i) immediately; the two forms are completely
>   equivalent."
 
> If arrays started at any subscript other than zero, then
>  a[subscript]
> could /not/ be equivalent to
>  *(a+subscript)

Yes, but a[i] could have been equivalent to *(a+i-1).

That might be a little strange, though. 

Note that in my programs I never write &a[i], but instead
always a+i. But with other definitions of a[i], you have to
be more careful. 

Fortran 66 programmers got used to all the +1 and -1 that come
about with array indexing. Fortran 77 added the ability to specify
the origin, but most arrays still index from 1.

Mathematicians still describe matrices as 1 origin.
 
> Consider: in a "arrays start at subscript 1" array,
>  array[1]
> would be equivalent to
>  *(array+0)
> and /not/ equivalent to
>  *(array+1)

-- glen

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just a curiosity about starting array indexing at 0 as opposed to 1 G G <gdotone@gmail.com> - 2015-11-21 18:50 -0800
  Re: just a curiosity about starting array indexing at 0 as opposed to 1 supercat@casperkitty.com - 2015-11-21 19:31 -0800
    Re: just a curiosity about starting array indexing at 0 as opposed to 1 Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-22 00:15 -0800
      Re: just a curiosity about starting array indexing at 0 as opposed to 1 supercat@casperkitty.com - 2015-11-22 07:20 -0800
        Re: just a curiosity about starting array indexing at 0 as opposed to 1 BartC <bc@freeuk.com> - 2015-11-22 16:22 +0000
          Re: just a curiosity about starting array indexing at 0 as opposed to 1 supercat@casperkitty.com - 2015-11-22 08:44 -0800
    Re: just a curiosity about starting array indexing at 0 as opposed to 1 Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2015-11-22 10:37 -0500
      Re: just a curiosity about starting array indexing at 0 as opposed to 1 BartC <bc@freeuk.com> - 2015-11-22 15:50 +0000
        Re: just a curiosity about starting array indexing at 0 as opposed to 1 Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2015-11-22 11:02 -0500
          Re: just a curiosity about starting array indexing at 0 as opposed to 1 BartC <bc@freeuk.com> - 2015-11-22 16:15 +0000
  Re: just a curiosity about starting array indexing at 0 as opposed to 1 Ian Collins <ian-news@hotmail.com> - 2015-11-22 16:42 +1300
    Re: just a curiosity about starting array indexing at 0 as opposed to 1 G G <gdotone@gmail.com> - 2015-11-21 19:55 -0800
    Re: just a curiosity about starting array indexing at 0 as opposed to 1 Keith Thompson <kst-u@mib.org> - 2015-11-23 11:01 -0800
      Re: just a curiosity about starting array indexing at 0 as opposed to 1 BartC <bc@freeuk.com> - 2015-11-23 19:18 +0000
        Re: just a curiosity about starting array indexing at 0 as opposed to 1 Keith Thompson <kst-u@mib.org> - 2015-11-23 11:26 -0800
          Re: just a curiosity about starting array indexing at 0 as opposed to 1 glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-23 22:54 +0000
            Re: just a curiosity about starting array indexing at 0 as opposed to 1 Robert Wessel <robertwessel2@yahoo.com> - 2015-11-23 18:37 -0600
              Re: just a curiosity about starting array indexing at 0 as opposed to 1 raltbos@xs4all.nl (Richard Bos) - 2015-11-24 15:22 +0000
      Re: just a curiosity about starting array indexing at 0 as opposed to 1 raltbos@xs4all.nl (Richard Bos) - 2015-11-24 15:13 +0000
  Re: just a curiosity about starting array indexing at 0 as opposed to 1 Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2015-11-22 01:21 -0500
    Re: just a curiosity about starting array indexing at 0 as opposed to 1 glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-22 15:00 +0000
      Re: just a curiosity about starting array indexing at 0 as opposed to 1 Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2015-11-22 10:15 -0500
        Re: just a curiosity about starting array indexing at 0 as opposed to 1 glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-23 13:47 +0000
          Re: just a curiosity about starting array indexing at 0 as opposed to 1 BartC <bc@freeuk.com> - 2015-11-23 14:50 +0000
            Re: just a curiosity about starting array indexing at 0 as opposed to 1 Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2015-11-23 12:01 -0500
              Re: just a curiosity about starting array indexing at 0 as opposed to 1 James Kuyper <jameskuyper@verizon.net> - 2015-11-23 12:12 -0500
                Re: just a curiosity about starting array indexing at 0 as opposed to 1 Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2015-11-23 12:57 -0500
            Re: just a curiosity about starting array indexing at 0 as opposed to 1 glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-23 23:08 +0000
          Re: just a curiosity about starting array indexing at 0 as opposed to 1 bert <bert.hutchings@btinternet.com> - 2015-11-23 08:52 -0800
      Re: just a curiosity about starting array indexing at 0 as opposed to 1 BartC <bc@freeuk.com> - 2015-11-22 15:42 +0000
        Re: just a curiosity about starting array indexing at 0 as opposed to 1 Keith Thompson <kst-u@mib.org> - 2015-11-22 12:36 -0800
        Re: just a curiosity about starting array indexing at 0 as opposed to 1 BartC <bc@freeuk.com> - 2015-11-22 21:06 +0000
  Re: just a curiosity about starting array indexing at 0 as opposed to 1 BartC <bc@freeuk.com> - 2015-11-22 10:28 +0000
    Re: just a curiosity about starting array indexing at 0 as opposed to 1 gazelle@shell.xmission.com (Kenny McCormack) - 2015-11-22 12:04 +0000
  Re: just a curiosity about starting array indexing at 0 as opposed to 1 Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-11-22 11:24 +0000
    Re: just a curiosity about starting array indexing at 0 as opposed to 1 G G <gdotone@gmail.com> - 2015-11-22 04:29 -0800
  Re: just a curiosity about starting array indexing at 0 as opposed to 1 see.my.homepage@gmail.com - 2015-11-22 04:54 -0800
    Re: just a curiosity about starting array indexing at 0 as opposed to 1 BartC <bc@freeuk.com> - 2015-11-22 13:43 +0000
    Re: just a curiosity about starting array indexing at 0 as opposed to 1 James Kuyper <jameskuyper@verizon.net> - 2015-11-22 11:04 -0500
  Re: just a curiosity about starting array indexing at 0 as opposed to 1 Jens Stuckelberger <Jens_Stuckelberger@nowhere.net> - 2015-11-22 15:29 +0000
  Re: just a curiosity about starting array indexing at 0 as opposed to 1 Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-22 14:06 -0800
  Re: just a curiosity about starting array indexing at 0 as opposed to 1 John Bode <jfbode1029@gmail.com> - 2015-11-23 07:49 -0800

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