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Re: rms from rosettacode

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On 12/27/2011 07:01 AM, superpollo wrote:
> James Kuyper ha scritto:
>> On 12/27/2011 05:25 AM, superpollo wrote:
>>> http://rosettacode.org/wiki/Averages/Root_mean_square#C
>>>
>>>
>>> ...
>>> [~/superpollo]$ cat rms_rc.c
>>> #include <stdio.h>
>>> #include <math.h>
>>>
>>> double rms(double *v, int n)
>>> {
>>>      int i;
>>>      double sum = 0.0;
>>>      for (i = 0; i < n; i++)
>>>          sum += v[i] * v[i];
>>>      return sqrt(sum / n);
>>> }
>>>
>>> int main()
>>> {
>>>      double v[] = { 1., 2., 3., 4., 5., 6., 7., 8., 9., 10. };
>>>      printf("%f\n", rms(v, sizeof(v) / sizeof(double)));
>>>
>>>      return 0;
>>> }
>>> [~/superpollo]$ cc -lm rms_rc.c && ./a.out
>>> 6.204837
>>> ...
>>>
>>> that works fine, but i am quite unhappy with having to say to the rms 
>>> function how big the array is... after all, i guess, shouldn't the 
>>> function be able to figure it out herself?
>>
>> How?
> 
> just in the same way as "main" does. no?

main() doesn't figure out the length itself; it's told the length by the
routine that calls main, by two different mechanisms: argc contains the
count of the arguments; since you're objecting to having to pass 'n' to
rms(), you should object, on the same ground, to the fact that the
implementation has to pass argc to main(). main() also uses the sentinel
value method I mentioned in the part of my message which you snipped:
argv[argc] is required to be a null pointer.
-- 
James Kuyper

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rms from rosettacode superpollo <superpollo@tznvy.pbz> - 2011-12-27 11:25 +0100
  Re: rms from rosettacode James Kuyper <jameskuyper@verizon.net> - 2011-12-27 06:48 -0500
    Re: rms from rosettacode superpollo <superpollo@tznvy.pbz> - 2011-12-27 13:01 +0100
      Re: rms from rosettacode James Kuyper <jameskuyper@verizon.net> - 2011-12-27 07:10 -0500
        Re: rms from rosettacode superpollo <superpollo@tznvy.pbz> - 2011-12-27 13:36 +0100
          Re: rms from rosettacode James Kuyper <jameskuyper@verizon.net> - 2011-12-27 10:04 -0500
    Re: rms from rosettacode Keith Thompson <kst-u@mib.org> - 2011-12-27 14:42 -0800
      Re: rms from rosettacode James Kuyper <jameskuyper@verizon.net> - 2011-12-27 18:46 -0500
  Re: rms from rosettacode 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-27 09:49 -0800
  Re: rms from rosettacode "BartC" <bc@freeuk.com> - 2011-12-27 18:14 +0000
    Re: rms from rosettacode superpollo <superpollo@tznvy.pbz> - 2011-12-27 19:33 +0100
      Re: rms from rosettacode jt@toerring.de (Jens Thoms Toerring) - 2011-12-27 19:04 +0000
        Re: rms from rosettacode Keith Thompson <kst-u@mib.org> - 2011-12-27 14:45 -0800
        Re: rms from rosettacode blp@cs.stanford.edu (Ben Pfaff) - 2011-12-27 14:57 -0800
      Re: rms from rosettacode "BartC" <bc@freeuk.com> - 2011-12-27 19:06 +0000
        Re: rms from rosettacode Bull in a China Blue Shop <chine.bleu@yahoo.com> - 2011-12-27 16:16 -0800
      Re: rms from rosettacode James Kuyper <jameskuyper@verizon.net> - 2011-12-27 14:11 -0500
      Re: rms from rosettacode Seebs <usenet-nospam@seebs.net> - 2011-12-27 20:13 +0000
      Re: rms from rosettacode Johann Klammer <klammerr@NOSPAM.aon.at> - 2011-12-28 00:23 +0100
      Re: rms from rosettacode 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-27 15:54 -0800
        Re: rms from rosettacode Keith Thompson <kst-u@mib.org> - 2011-12-27 22:53 -0800
          Re: rms from rosettacode Seebs <usenet-nospam@seebs.net> - 2011-12-28 06:29 +0000
          Re: rms from rosettacode 88888 Dihedral <dihedral88888@googlemail.com> - 2011-12-28 02:45 -0800
  Re: rms from rosettacode Kaz Kylheku <kaz@kylheku.com> - 2011-12-27 19:53 +0000
    Re: rms from rosettacode Seebs <usenet-nospam@seebs.net> - 2011-12-27 20:13 +0000
    Re: rms from rosettacode superpollo <superpollo@tznvy.pbz> - 2011-12-27 21:31 +0100
      Re: rms from rosettacode Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-12-27 20:49 -0500
        Re: rms from rosettacode superpollo <superpollo@tznvy.pbz> - 2011-12-28 11:42 +0100
          Re: rms from rosettacode Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-12-29 08:18 -0800
        Re: rms from rosettacode superpollo <superpollo@tznvy.pbz> - 2011-12-28 11:54 +0100
          Re: rms from rosettacode Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-12-29 04:12 +0200
            Re: rms from rosettacode superpollo <superpollo@tznvy.pbz> - 2011-12-29 14:38 +0100
        Re: rms from rosettacode Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-12-28 02:26 -0800
          Re: rms from rosettacode Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-12-28 21:35 -0500
            Re: rms from rosettacode superpollo <superpollo@tznvy.pbz> - 2011-12-29 14:10 +0100
        Re: rms from rosettacode James Kuyper <jameskuyper@verizon.net> - 2011-12-28 08:03 -0500
          Re: rms from rosettacode "BartC" <bc@freeuk.com> - 2011-12-28 13:32 +0000
            Re: rms from rosettacode Dr Nick <3-nospam@temporary-address.org.uk> - 2011-12-28 13:41 +0000
            Re: rms from rosettacode Kaz Kylheku <kaz@kylheku.com> - 2011-12-28 19:29 +0000
            Re: rms from rosettacode Keith Thompson <kst-u@mib.org> - 2011-12-28 13:47 -0800
            Re: rms from rosettacode Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-12-29 04:19 +0200
      Re: rms from rosettacode Kaz Kylheku <kaz@kylheku.com> - 2011-12-28 19:11 +0000

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