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Re: Return value for error

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pozz <pozzugno@gmail.com> writes:
> A very simple question. What do you use as the return value of a
> function for error/ok results?
> I can't decide between 0 for error and !=0 for ok, or 0 for ok and !=0
> for errors.
>
> If !=0 is ok, I can write:
>
>   if (myfunction()) printf("OK\n");
>
> but I have only one error code (0), while, in some cases, it could be
> useful to have more informations about the type of error.
>
> If !=0 is error I can have several error codes, but I have to write
>
>   if (!myfuction()) printf("OK\n");
>
> that apparently seems myfunction has not terminated with success.

Just because you're checking whether a result is equal to zero, you
don't *have* to use the "!" operator.

Personally, I use "!" only for values that are logically Boolean
(zero means false, anything non-zero means true, and there's no
meaningful distinction among different non-zero values).  So I
might write the above as:

    if (myfunction() == 0) printf("OK\n");

Or I might define a constant of some sort with the value 0
to make the code clearer, as you suggest:

> Another strategy is to define custom error code:
>
> #define ERROR_OK  0
> #define ERROR_UNDEFINED 1
> #define ERROR_WRONGVALUE 2
>
> and so on, and always write:
>
>   if (myfuction() == ERROR_OK) printf("OK\n");

(but not with a name that's reserved to the implementation).

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Nokia
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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Return value for error pozz <pozzugno@gmail.com> - 2011-05-03 01:31 -0700
  Re: Return value for error jacob navia <jacob@spamsink.net> - 2011-05-03 10:46 +0200
  Re: Return value for error Ike Naar <ike@otaku.freeshell.org> - 2011-05-03 09:04 +0000
    Re: Return value for error Ian Collins <ian-news@hotmail.com> - 2011-05-03 21:19 +1200
  Re: Return value for error James Kuyper <jameskuyper@verizon.net> - 2011-05-03 06:26 -0400
    Re: Return value for error Keith Thompson <kst-u@mib.org> - 2011-05-03 12:03 -0700
      Re: Return value for error "Kleuskes & Moos" <kleuske@xs4all.nl> - 2011-05-04 05:15 -0700
        Re: Return value for error Keith Thompson <kst-u@mib.org> - 2011-05-04 08:26 -0700
          Re: Return value for error "Kleuskes & Moos" <kleuske@xs4all.nl> - 2011-05-04 17:08 -0700
            Re: Return value for error Keith Thompson <kst-u@mib.org> - 2011-05-04 17:54 -0700
              Re: Return value for error "Kleuskes & Moos" <kleuske@xs4all.nl> - 2011-05-05 12:03 -0700
  Re: Return value for error James Dow Allen <jdallen2000@yahoo.com> - 2011-05-03 03:45 -0700
    Re: Return value for error Jorgen Grahn <grahn+nntp@snipabacken.se> - 2011-05-03 20:50 +0000
  Re: Return value for error pete <pfiland@mindspring.com> - 2011-05-03 07:50 -0400
    Re: Return value for error Keith Thompson <kst-u@mib.org> - 2011-05-03 12:04 -0700
  Re: Return value for error Martin Ambuhl <mambuhl@earthlink.net> - 2011-05-03 07:59 -0400
  Re: Return value for error Mark Storkamp <mstorkamp@yahoo.com> - 2011-05-03 08:46 -0500
  Re: Return value for error Stephen Sprunk <stephen@sprunk.org> - 2011-05-03 10:13 -0500
    Re: Return value for error William Ahern <william@wilbur.25thandClement.com> - 2011-05-03 13:08 -0700
  Re: Return value for error Kenneth Brody <kenbrody@spamcop.net> - 2011-05-03 13:23 -0400
    Re: Return value for error Peter Nilsson <airia@acay.com.au> - 2011-05-03 16:01 -0700
    Re: Return value for error Nobody <nobody@nowhere.com> - 2011-05-05 07:21 +0100
      Re: Return value for error Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-05-05 15:13 +0100
        Re: Return value for error Nobody <nobody@nowhere.com> - 2011-05-06 03:51 +0100
          Re: Return value for error James Kuyper <jameskuyper@verizon.net> - 2011-05-05 23:38 -0400
      Re: Return value for error Keith Thompson <kst-u@mib.org> - 2011-05-05 08:44 -0700
        Re: Return value for error Seebs <usenet-nospam@seebs.net> - 2011-05-05 20:49 +0000
          Re: Return value for error Keith Thompson <kst-u@mib.org> - 2011-05-05 14:10 -0700
            Re: Return value for error Seebs <usenet-nospam@seebs.net> - 2011-05-06 00:26 +0000
  Re: Return value for error Keith Thompson <kst-u@mib.org> - 2011-05-03 12:09 -0700

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