Re: qsort() standard functions

From	Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups	comp.lang.c
Subject	Re: qsort() standard functions
Date	2019-04-26 17:46 +0100
Organization	A noiseless patient Spider
Message-ID	<87ef5osoib.fsf@bsb.me.uk> (permalink)
References	(13 earlier) <20190425234955.d5e41956e47d87a13c5d2be8@gmail.com> <87ef5pu5cf.fsf@bsb.me.uk> <20190426130638.ee2504b98c14cb6c666f95b8@g{oogle}mail.com> <87mukdrler.fsf@bsb.me.uk> <20190426164329.8cd319730cce76ab734f5ac6@g{oogle}mail.com>

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Anton Shepelev <anton.txt@g{oogle}mail.com> writes:

> Ben Bacarisse:
>
>>>>Also, did you mean for the "const"s to be the other way
>>>>round?
>>>>  typedef int (*comp_f)(const void *data, int i, int j, void * extra);
>>>
>>>No.  The extra data (`extra') should not be modified in
>>>the process of sorting, whereas the data to sort (`data')
>>>should.  This `extra' parameter may point to whatever
>>>additional information the user wants to supply.  When
>>>sorting a table, for example, it may contain the column by
>>>which to sort
>>
>>Hmm... I think that's wrong (about what's const and what
>>isn't).  The data items should /not/ be modified simply by
>>the act of comparing one to another,
>
> But they are modified in swap_f, and I intended to make the
> parameter type the same throughout.

That, to me, is a false consistency.  The two functions are not the
same.  A swap function has to modify the pointer targets, a comparison
function should not.

> It is better to accept
> a `void *' and pass on as `const void *' to the comparison
> function.

I don't understand this.

>>but the extra data might very well be.  For example, I've
>>done collection of statistics via the 'extra' data pointer.
>
> This is the only case of modifying `extra' that I could
> think of, but it belongs more to debugging than to actual
> use, so I didn't provide it.

I think it's better to consider what's logical rather than what you (or
I) can think of.  But there are certainly other uses of non-const target
extra data.

> Not a big deal if I do,
> though, except if one is a devotee of const correctness...

Again, I'm not side what you mean here.  It seems as if you are saying
that if you did make 'extra' a 'const void *', that would annoy devotees
of const correctness.  Seems like the other way round to me, but many
I've missed your meaning.

-- 
Ben.

Thread

qsort() standard functions rick.c.hodgin@gmail.com - 2019-04-24 09:08 -0700
  Re: qsort() standard functions gazelle@shell.xmission.com (Kenny McCormack) - 2019-04-24 16:12 +0000
    Re: qsort() standard functions rick.c.hodgin@gmail.com - 2019-04-24 09:18 -0700
      Re: qsort() standard functions Chad <cdalten@gmail.com> - 2019-05-02 12:02 -0700
    Re: qsort() standard functions Real Troll <real.troll@trolls.com> - 2019-04-24 22:30 -0400
      Re: qsort() standard functions "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-04-24 19:32 -0700
        Re: qsort() standard functions Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-04-25 10:19 +0000
          Re: qsort() standard functions rick.c.hodgin@gmail.com - 2019-04-25 04:09 -0700
            Re: qsort() standard functions Richard Damon <Richard@Damon-Family.org> - 2019-04-25 08:13 -0400
              Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-25 06:39 -0700
              Re: qsort() standard functions already5chosen@yahoo.com - 2019-04-25 07:23 -0700
      Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-25 00:39 -0700
        Re: qsort() standard functions Real Troll <Real.Troll@Trolls.com> - 2019-04-25 23:27 +0100
  Re: qsort() standard functions John Bode <jfbode1029@gmail.com> - 2019-04-24 09:34 -0700
    Re: qsort() standard functions "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-04-24 09:47 -0700
    Re: qsort() standard functions John Bode <jfbode1029@gmail.com> - 2019-04-24 09:47 -0700
      Re: qsort() standard functions "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-04-24 12:54 -0400
        Re: qsort() standard functions John Bode <jfbode1029@gmail.com> - 2019-04-24 11:33 -0700
          Re: qsort() standard functions "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-04-24 14:41 -0400
            Re: qsort() standard functions John Bode <jfbode1029@gmail.com> - 2019-04-24 11:52 -0700
              Re: qsort() standard functions gazelle@shell.xmission.com (Kenny McCormack) - 2019-04-24 19:12 +0000
              Re: qsort() standard functions "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-04-24 16:05 -0400
                Re: qsort() standard functions queequeg@trust.no1 (Queequeg) - 2019-04-24 20:39 +0000
            Re: qsort() standard functions James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-04-24 16:33 -0700
      Re: qsort() standard functions gazelle@shell.xmission.com (Kenny McCormack) - 2019-04-24 19:18 +0000
        Re: qsort() standard functions Bart <bc@freeuk.com> - 2019-04-24 20:28 +0100
          Re: qsort() standard functions gazelle@shell.xmission.com (Kenny McCormack) - 2019-04-24 21:27 +0000
        Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-24 12:31 -0700
        Re: qsort() standard functions John Bode <jfbode1029@gmail.com> - 2019-04-24 13:02 -0700
          Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-24 13:41 -0700
            Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-24 14:00 -0700
              Re: qsort() standard functions Anton Shepelev <anton.txt@gmail.com> - 2019-04-25 00:22 +0300
                Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-24 15:04 -0700
                Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-24 15:20 -0700
                Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-24 15:40 -0700
                Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-24 15:57 -0700
                Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-24 16:06 -0700
                Re: qsort() standard functions Anton Shepelev <anton.txt@gmail.com> - 2019-04-25 23:49 +0300
                Re: qsort() standard functions Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-04-25 22:45 +0100
                Re: qsort() standard functions Bart <bc@freeuk.com> - 2019-04-25 23:00 +0100
                Re: qsort() standard functions Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-04-25 23:24 +0100
                Re: qsort() standard functions Real Troll <Real.Troll@Trolls.com> - 2019-04-25 23:20 +0100
                Re: qsort() standard functions Anton Shepelev <anton.txt@g{oogle}mail.com> - 2019-04-26 13:06 +0300
                Re: qsort() standard functions Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-04-26 13:38 +0100
                Re: qsort() standard functions Anton Shepelev <anton.txt@g{oogle}mail.com> - 2019-04-26 16:43 +0300
                Re: qsort() standard functions Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-04-26 17:46 +0100
                Re: qsort() standard functions Anton Shepelev <anton.txt@gmail.com> - 2019-04-27 14:55 +0300
                Re: qsort() standard functions Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-04-27 14:59 +0100
                Re: qsort() standard functions Robert Wessel <robertwessel2@yahoo.com> - 2019-04-27 11:41 -0500
                Re: qsort() standard functions Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-05-02 09:46 -0700
                Re: qsort() standard functions Anton Shepelev <anton.txt@gmail.com> - 2019-05-02 20:35 +0300
                Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-05-02 15:35 -0700
                Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-05-05 04:39 -0700
                Re: qsort() standard functions Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-05-04 07:35 -0700
                Re: qsort() standard functions Anton Shepelev <anton.txt@gmail.com> - 2019-05-05 00:01 +0300
                Re: qsort() standard functions Anton Shepelev <anton.txt@gmail.com> - 2019-05-02 15:11 +0300
                Re: qsort() standard functions Ben Bacarisse <ben.usenet@bsb.me.uk> - 2019-05-02 16:36 +0100
                Re: qsort() standard functions Anton Shepelev <anton.txt@gmail.com> - 2019-04-27 14:47 +0300
                Re: qsort() standard functions Robert Wessel <robertwessel2@yahoo.com> - 2019-04-27 08:30 -0500
                Re: qsort() standard functions Anton Shepelev <anton.txt@gmail.com> - 2019-05-02 14:52 +0300
                Re: qsort() standard functions Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-05-04 07:13 -0700
                Re: qsort() standard functions Anton Shepelev <anton.txt@gmail.com> - 2019-05-05 22:57 +0300
                Re: qsort() standard functions David Brown <david.brown@hesbynett.no> - 2019-05-06 10:09 +0200
                Re: qsort() standard functions Tim Rentsch <tr.17687@z991.linuxsc.com> - 2019-06-01 05:22 -0700
                Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-25 17:09 -0700
                Re: qsort() standard functions Bart <bc@freeuk.com> - 2019-04-26 10:58 +0100
                Re: qsort() standard functions mark.bluemel@gmail.com - 2019-04-26 03:59 -0700
                Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-26 06:34 -0700
                Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-26 07:16 -0700
                Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-26 07:45 -0700
                Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-26 08:29 -0700
                Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-26 12:06 -0700
                Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-26 13:09 -0700
                Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-26 13:37 -0700
                Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-26 14:05 -0700
                Re: qsort() standard functions Anton Shepelev <anton.txt@gmail.com> - 2019-04-27 14:59 +0300
                Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-27 06:19 -0700
                Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-27 06:32 -0700
  Re: qsort() standard functions Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2019-04-24 10:54 -0600
    Re: qsort() standard functions "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-04-24 10:10 -0700
    Re: qsort() standard functions Anton Shepelev <anton.txt@gmail.com> - 2019-04-25 00:06 +0300
  Re: qsort() standard functions scott@slp53.sl.home (Scott Lurndal) - 2019-04-24 17:37 +0000
    Re: qsort() standard functions "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-04-24 10:56 -0700
      Re: qsort() standard functions Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2019-04-24 12:12 -0600
        Re: qsort() standard functions "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-04-24 14:27 -0400
          Re: qsort() standard functions John Bode <jfbode1029@gmail.com> - 2019-04-24 11:44 -0700
            Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-24 11:57 -0700
              Re: qsort() standard functions fir <profesor.fir@gmail.com> - 2019-04-24 12:04 -0700
            Re: qsort() standard functions nobody@example.org (Scott) - 2019-04-25 01:16 +0000
              Re: qsort() standard functions James Kuyper <jameskuyper@alumni.caltech.edu> - 2019-04-24 21:38 -0400
  Re: qsort() standard functions "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-04-24 14:42 -0400
    Re: qsort() standard functions David Brown <david.brown@hesbynett.no> - 2019-04-24 22:13 +0200
    Re: qsort() standard functions queequeg@trust.no1 (Queequeg) - 2019-04-24 20:46 +0000
  Re: qsort() standard functions jadill33@gmail.com - 2019-04-24 14:01 -0700
  Re: qsort() standard functions "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2019-04-24 15:41 -0700
  Re: qsort() standard functions "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2019-04-26 22:24 +0800
    Re: qsort() standard functions Anton Shepelev <anton.txt@gmail.com> - 2019-05-02 15:05 +0300
      Re: qsort() standard functions "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2019-05-03 17:02 +0800
        Re: qsort() standard functions Chad <cdalten@gmail.com> - 2019-05-03 10:10 -0700
          Re: qsort() standard functions "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2019-05-04 01:22 +0800
            Re: qsort() standard functions Chad <cdalten@gmail.com> - 2019-05-03 15:14 -0700
              [OT]Eternal.... programmer? "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2019-05-04 06:20 +0800
                Re: [OT]Eternal.... programmer? Chad <cdalten@gmail.com> - 2019-05-04 05:53 -0700

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