Re: Copy array with small changes

From	Spiros Bousbouras <spibou@gmail.com>
Newsgroups	comp.lang.c
Subject	Re: Copy array with small changes
References	<p848dh$oko$1@dont-email.me> <qShpC.133290$Zg.23093@fx21.am4> <SJspC.109257$qj4.65637@fx37.am4>
Message-ID	<NvupC.120298$856.70911@fx42.am4> (permalink)
Organization	virginmedia.com
Date	2018-03-12 12:37 +0000

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On Mon, 12 Mar 2018 10:35:32 +0000
bartc <bc@freeuk.com> wrote:
> On 11/03/2018 22:13, Spiros Bousbouras wrote:
> > On Sun, 11 Mar 2018 22:51:40 +0100
> > Noob <root@127.0.0.1> wrote:
> >> Hello,
> >>
> >> I'm writing a toy program where I have a function that copies
> >> a small sorted array (less than 12 ints) while making two small
> >> changes: remove two elements, insert one element.
> >>
> >> The function prototype is:
> >>
> >> void update_array(int *arr, int n, int zi, int zj, int val);
> >>
> >> arr = the original array, sorted by increasing values
> >> n = number of elements < N = 12
> >> zi = 1st index to remove
> >> zj = 2nd index to remove
> >> val = new value to insert while keeping the array sorted
> >>
> >> Here's my current implementation:
> >>
> >> void update_array(int *arr, int n, int zi, int zj, int val)
> > 
> > void update_array(const int * const arr , const size_t n ,
> >                    const size_t zi , const size_t zj , const int val)
> > 
> > Actually something like  arrsz  is a better name than  n.
> 
> No, this suggests array size which in C usually means byte-size, not 
> number of elements.

You have any statistics to back this up ? I always use it to mean number
of elements.

> You might have pointed out that 'update-array' is 
> misnamed as the array passed is not modified.

Sure.

> >But since the
> > function is short it doesn't matter that much.
> 
> Well, it /had/ been short until you introduced all these consts! (Is 
> there really a benefit from declaring individual int parameters as const?)

It remains short. I thought the  const  declarations might help with
optimisation but the only way to tell is to test.

> Also, wasn't the OP requesting something less ugly? And something a bit 
> faster? Stipulating possible 64-bit types for n, zi and zj, when it was 
> stated that all these will be less than 12, probably won't help.

size_t  is the canonical way to refer to array sizes and array indexes ;
anything else gives one more to think and worry about (like type conversions)
in an area where dangerous errors happen most often. So  size_t  is the
default option unless one has good reasons to do otherwise. If on a machine
size_t  is 64 bit then almost certainly it will be a 64 bit processor so 32
bit integer operations aren't going to be faster than 64 bit. In any case the
opening poster can test ; if using  int  achieves faster speed than using
size_t  and it makes a difference to him then this would be a good reason to
prefer  int  over  size_t .

-- 
vlaho.ninja/prog

Thread

Copy array with small changes Noob <root@127.0.0.1> - 2018-03-11 22:51 +0100
  Re: Copy array with small changes supercat@casperkitty.com - 2018-03-11 15:11 -0700
  Re: Copy array with small changes Richard Damon <Richard@Damon-Family.org> - 2018-03-11 18:12 -0400
    Re: Copy array with small changes Spiros Bousbouras <spibou@gmail.com> - 2018-03-11 22:35 +0000
      Re: Copy array with small changes Richard Damon <Richard@Damon-Family.org> - 2018-03-13 13:10 -0400
  Re: Copy array with small changes Spiros Bousbouras <spibou@gmail.com> - 2018-03-11 22:13 +0000
    Re: Copy array with small changes Spiros Bousbouras <spibou@gmail.com> - 2018-03-12 00:04 +0000
    Re: Copy array with small changes bartc <bc@freeuk.com> - 2018-03-12 10:35 +0000
      Re: Copy array with small changes Spiros Bousbouras <spibou@gmail.com> - 2018-03-12 12:37 +0000
        Re: Copy array with small changes bartc <bc@freeuk.com> - 2018-03-12 13:10 +0000
        Re: Copy array with small changes Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-03-12 13:34 +0000
          Re: Copy array with small changes Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-17 09:22 -0700
        Re: Copy array with small changes mark.bluemel@gmail.com - 2018-03-12 07:47 -0700
          Re: Copy array with small changes bartc <bc@freeuk.com> - 2018-03-12 14:56 +0000
            Re: Copy array with small changes Spiros Bousbouras <spibou@gmail.com> - 2018-03-12 15:14 +0000
            Re: Copy array with small changes mark.bluemel@gmail.com - 2018-03-12 08:53 -0700
        Re: Copy array with small changes Keith Thompson <kst-u@mib.org> - 2018-03-12 09:08 -0700
          Re: Copy array with small changes supercat@casperkitty.com - 2018-03-12 09:57 -0700
            Re: Copy array with small changes Richard Damon <Richard@Damon-Family.org> - 2018-03-13 13:21 -0400
    Re: Copy array with small changes Noob <root@127.0.0.1> - 2018-03-12 15:25 +0100
      Re: Copy array with small changes Spiros Bousbouras <spibou@gmail.com> - 2018-03-12 15:09 +0000
  Re: Copy array with small changes Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-03-12 06:59 +0000
    Re: Copy array with small changes Noob <root@127.0.0.1> - 2018-03-12 15:55 +0100
      Re: Copy array with small changes bartc <bc@freeuk.com> - 2018-03-12 15:07 +0000
      Re: Copy array with small changes mark.bluemel@gmail.com - 2018-03-12 09:03 -0700
      Re: Copy array with small changes Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-03-12 17:42 +0000
        Re: Copy array with small changes Noob <root@127.0.0.1> - 2018-03-12 23:33 +0100
          Re: Copy array with small changes Wouter Verhelst <w@uter.be> - 2018-03-12 23:44 +0100
          Re: Copy array with small changes Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-17 09:48 -0700
            Re: Copy array with small changes Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-18 03:31 -0700
            Re: Copy array with small changes Noob <root@127.0.0.1> - 2018-03-22 17:10 +0100
        Re: Copy array with small changes Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-17 09:24 -0700
          Re: Copy array with small changes Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-03-17 18:04 +0000
            Re: Copy array with small changes Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-26 22:55 -0700
              Re: Copy array with small changes Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-03-27 15:28 +0100
                Re: Copy array with small changes Steven Petruzzellis <frelwizzen@gmail.com> - 2018-03-28 14:42 -0700
      Re: Copy array with small changes Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-03-13 12:46 +0000
  Re: Copy array with small changes Anton Shepelev <anton.txt@gmail.com> - 2018-03-12 22:36 +0300
  Re: Copy array with small changes Wouter Verhelst <w@uter.be> - 2018-03-12 23:32 +0100
    Re: Copy array with small changes Wouter Verhelst <w@uter.be> - 2018-03-13 10:42 +0100
    Re: Copy array with small changes Noob <root@127.0.0.1> - 2018-03-13 11:37 +0100
      Re: Copy array with small changes Wouter Verhelst <w@uter.be> - 2018-03-13 21:27 +0100
  Re: Copy array with small changes Tim Rentsch <txr@alumni.caltech.edu> - 2018-03-17 09:55 -0700

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