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Re: Synthetic 'unless' keyword

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On 04/08/2016 10:44, Jens Thoms Toerring wrote:
> Hi,
>
>   everyone uses 'if' probably hundreds of times a day.
> But in some situations I'd feel that being able to use
> 'unless' instead, as in the trivial example
>
>   unless (argc > 1) {
>       fprintf(stderr, "Missing argument(s)\n");
>       return EXIT_FAILURE;
>   }
>
> might contribute to the readability of the code. Now,
> 'unless' isn't a C keyword (as it is in some other
> languages, e.g. Perl) but it seems easy to use a
> define like this
>
> #define unless(expr) if (!(expr))
>
> What possibly could go wrong (except that 'unless' may
> be used as a variable name somewhere

I can't see a problem (except that people like to have macro names in 
capitals).

I use 'unless' in another language which can be translated to C. And 
there the translation uses exactly the same construct as yours, with a 
few extra parentheses:

Original source:

     unless a=0 then
         b:=c/a
     end

C output:

     if ((!(a==0)))
     {
         b=(c/a);
     }

(I can also write the above as:

     b:=c/a unless a=0

but this goes beyond the capabilities of the macro system.)

One thing about 'unless' is that it can get confusing in a chain:

  unless (a) {x;}
  else unless (b) {y;}
  else if (c) {z;}

So I keep uses of it simple.

  and that editors
> with syntax highlighting won't recognize it)? Or would
> it be to "alien" to most C programmers?

As someone has suggested, if you want to enhance the language with such 
macros, then you should be able to do so.

I would also add ones such as LEN() which replaces 
sizeof(a)/sizeof(a[0]), which saves writing the latter hundreds of 
times. Such things are not popular in this newsgroup, but ignore that...

Not having syntax highlighting support can be a problem. Although 
individual apps might have a way of extending the set of keywords that 
are recognised.

-- 
Bartc

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Thread

Synthetic 'unless' keyword jt@toerring.de (Jens Thoms Toerring) - 2016-08-04 09:44 +0000
  Re: Synthetic 'unless' keyword David Brown <david.brown@hesbynett.no> - 2016-08-04 12:21 +0200
  Re: Synthetic 'unless' keyword Mark Storkamp <mstorkamp@yahoo.com> - 2016-08-04 07:01 -0500
    Re: Synthetic 'unless' keyword bert <bert.hutchings@btinternet.com> - 2016-08-04 05:42 -0700
    Re: Synthetic 'unless' keyword Keith Thompson <kst-u@mib.org> - 2016-08-04 08:45 -0700
      Re: Synthetic 'unless' keyword Philip Lantz <prl@canterey.us> - 2016-08-04 21:55 -0700
      Re: Synthetic 'unless' keyword BartC <bc@freeuk.com> - 2016-08-05 10:08 +0100
    Re: Synthetic 'unless' keyword Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-05 01:17 -0700
      Re: Synthetic 'unless' keyword BartC <bc@freeuk.com> - 2016-08-05 10:01 +0100
        Re: Synthetic 'unless' keyword Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-05 04:34 -0700
      Re: Synthetic 'unless' keyword Mark Storkamp <mstorkamp@yahoo.com> - 2016-08-05 09:37 -0500
        Re: Synthetic 'unless' keyword Malcolm McLean <malcolm.mclean5@btinternet.com> - 2016-08-06 02:28 -0700
  Re: Synthetic 'unless' keyword jt@toerring.de (Jens Thoms Toerring) - 2016-08-04 13:38 +0000
  Re: Synthetic 'unless' keyword BartC <bc@freeuk.com> - 2016-08-04 15:04 +0100
  Re: Synthetic 'unless' keyword mark.bluemel@gmail.com - 2016-08-04 07:06 -0700
  Re: Synthetic 'unless' keyword Keith Thompson <kst-u@mib.org> - 2016-08-04 08:52 -0700
    Re: Synthetic 'unless' keyword supercat@casperkitty.com - 2016-08-04 09:45 -0700
      Re: Synthetic 'unless' keyword Keith Thompson <kst-u@mib.org> - 2016-08-04 10:23 -0700
        Re: Synthetic 'unless' keyword Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-04 19:39 +0100
          Re: Synthetic 'unless' keyword supercat@casperkitty.com - 2016-08-04 12:02 -0700
            Re: Synthetic 'unless' keyword Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-04 20:33 +0100
            Re: Synthetic 'unless' keyword BartC <bc@freeuk.com> - 2016-08-04 20:42 +0100
              Re: Synthetic 'unless' keyword David Brown <david.brown@hesbynett.no> - 2016-08-05 13:14 +0200
                Re: Synthetic 'unless' keyword Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-05 12:41 +0100
    Re: Synthetic 'unless' keyword mark.bluemel@gmail.com - 2016-08-05 00:53 -0700
  Re: Synthetic 'unless' keyword Jerry Stuckle <jstucklex@attglobal.net> - 2016-08-04 16:43 -0400
    Re: Synthetic 'unless' keyword David Brown <david.brown@hesbynett.no> - 2016-08-05 13:16 +0200
  Re: Synthetic 'unless' keyword jt@toerring.de (Jens Thoms Toerring) - 2016-08-04 23:16 +0000
    Re: Synthetic 'unless' keyword Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-08-05 00:35 +0100
    Re: Synthetic 'unless' keyword Tim Rentsch <txr@alumni.caltech.edu> - 2016-08-04 20:13 -0700
    Re: Synthetic 'unless' keyword Tim Rentsch <txr@alumni.caltech.edu> - 2016-08-05 04:57 -0700
      Re: Synthetic 'unless' keyword BartC <bc@freeuk.com> - 2016-08-05 13:15 +0100
        Re: Synthetic 'unless' keyword Tim Rentsch <txr@alumni.caltech.edu> - 2016-08-18 08:11 -0700
          Re: Synthetic 'unless' keyword BartC <bc@freeuk.com> - 2016-08-18 16:36 +0100
            Re: Synthetic 'unless' keyword supercat@casperkitty.com - 2016-08-18 10:20 -0700
  Re: Synthetic 'unless' keyword Paul N <gw7rib@aol.com> - 2016-08-07 12:56 -0700

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