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Re: Is there any way to refer to another array in qsort's compare function?

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Stone <stonekyx@gmail.com> writes:

> Here's the problem.
>
> I wrote a function 'int my_compare(const void *, const void *);' and
> passed it to qsort() of stdlib.h, in order to sort an array named
> *ptr* which contains indices of another array *data*. By that I
> intended to sort elements of *ptr* (i.e. ptr[i]) using data[ptr[i]] as
> the key value.
>
> However, the *data* array was defined as static in main(), and seemed
> not easy to access in my_compare(). Is there any way to achieve this?

Not that I know of.  It's a design flaw in the standard library IMO -
any function that takes a user provided function and calls it in this
way should take an extra, void *, parameter that it passes to the called
function.  After all, it can always be NULL.  In this case, it could
carry a pointer to your "data" array.

There are non-standard versions of qsort (usually called qsort_r or
qsort_s) that do this, but whether you have access to one, and how
concerned you are about portability will feature in your decision on
whether to this or whether to make your array global (or to have a
global pointer to it - suitably named and identified).

Anyone know if this is going to appear in standard C (and if not, why
not?; it seems a clear flaw to me).
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Is there any way to refer to another array in qsort's compare function? Stone <stonekyx@gmail.com> - 2011-12-29 00:27 -0800
  Re: Is there any way to refer to another array in qsort's compare function? Dr Nick <3-nospam@temporary-address.org.uk> - 2011-12-29 08:57 +0000
  Re: Is there any way to refer to another array in qsort's compare function? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-12-29 11:58 +0000
    Re: Is there any way to refer to another array in qsort's compare function? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-29 04:20 -0800
      Re: Is there any way to refer to another array in qsort's compare function? Dr Nick <3-nospam@temporary-address.org.uk> - 2011-12-29 12:37 +0000
        Re: Is there any way to refer to another array in qsort's compare function? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-29 04:48 -0800
          Re: Is there any way to refer to another array in qsort's compare function? Dr Nick <3-nospam@temporary-address.org.uk> - 2011-12-29 12:59 +0000
            Re: Is there any way to refer to another array in qsort's compare function? Geoff <geoff@invalid.invalid> - 2011-12-29 10:09 -0800
              Re: Is there any way to refer to another array in qsort's compare function? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-29 17:50 -0800
                Re: Is there any way to refer to another array in qsort's compare function? Geoff <geoff@invalid.invalid> - 2011-12-29 19:29 -0800
                Re: Is there any way to refer to another array in qsort's compare function? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-30 00:36 -0800
                Re: Is there any way to refer to another array in qsort's compare function? Bull in a China Blue Shop <chine.bleu@yahoo.com> - 2011-12-30 00:52 -0800
                Re: Is there any way to refer to another array in qsort's compare function? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-30 02:16 -0800
              Re: Is there any way to refer to another array in qsort's compare function? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-29 18:01 -0800
            Re: Is there any way to refer to another array in qsort's compare function? James Kuyper <jameskuyper@verizon.net> - 2011-12-29 13:21 -0500
        Re: Is there any way to refer to another array in qsort's compare function? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-30 23:18 -0800
    Re: Is there any way to refer to another array in qsort's compare function? 88888 Dihedral <dihedral88888@googlemail.com> - 2012-01-07 23:40 -0800
      Re: Is there any way to refer to another array in qsort's compare function? pete <pfiland@mindspring.com> - 2012-01-08 07:26 -0500
        Re: Is there any way to refer to another array in qsort's compare function? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-08 12:50 +0000
          Re: Is there any way to refer to another array in qsort's compare function? 88888 Dihedral <dihedral88888@googlemail.com> - 2012-01-08 06:02 -0800
        Re: Is there any way to refer to another array in qsort's compare function? Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-01-17 12:35 +0200
  Re: Is there any way to refer to another array in qsort's compare function? Bull in a China Blue Shop <chine.bleu@yahoo.com> - 2011-12-29 05:07 -0800
    Re: Is there any way to refer to another array in qsort's compare function? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-12-29 14:16 +0000
      Re: Is there any way to refer to another array in qsort's compare function? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-12-29 15:29 +0000
        Re: Is there any way to refer to another array in qsort's compare function? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-29 09:33 -0800
        Re: Is there any way to refer to another array in qsort's compare function? 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-29 15:40 -0800
  Re: Is there any way to refer to another array in qsort's compare function? James Kuyper <jameskuyper@verizon.net> - 2011-12-29 10:50 -0500
  Re: Is there any way to refer to another array in qsort's compare function? pete <pfiland@mindspring.com> - 2012-01-07 20:50 -0500

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