Date: Sun, 4 Apr 2010 14:48:14 -0400 From: Alejandro Imass <ait@p2ee.org> To: Polytropon <freebsd@edvax.de> Cc: Chad Perrin <perrin@apotheon.com>, FreeBSD Mailing List <freebsd-questions@freebsd.org> Subject: Re: perl qstn... Message-ID: <o2oa14066a01004041148zd4ef8167q32b04d58daec8f9f@mail.gmail.com> In-Reply-To: <20100404201442.b456044e.freebsd@edvax.de> References: <20100403210610.GA4135@thought.org> <4BB8108A.9080104@FreeBSD.org> <1270371713.5861.98.camel@tao.thought.org> <86aatjnsts.fsf@red.stonehenge.com> <861vevnsow.fsf@red.stonehenge.com> <j2ya14066a01004040945z39191770k2f025752317fb14a@mail.gmail.com> <20100404163353.GA15198@guilt.hydra> <20100404201442.b456044e.freebsd@edvax.de>
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On Sun, Apr 4, 2010 at 2:14 PM, Polytropon <freebsd@edvax.de> wrote:
> On Sun, 4 Apr 2010 10:33:53 -0600, Chad Perrin <perrin@apotheon.com> wrot=
e:
>> On Sun, Apr 04, 2010 at 12:45:30PM -0400, Alejandro Imass wrote:
>> > did you mean unless? ;-)
>>
>> I find "if" to be clearer than "unless" when there's an "else", so
>> instead of making that "if" into an "unless", I'd just swap the
>> conditional actions.
>
> A quite language-independent technical sidenote :-) ...
>
<grin>
> If your if() conditional is to test an exception, something
> that you usually DON'T want to happen - i. e. missing command
> line parameters - you can use the ! negation operator to
> indicate this in the if() argument.
>
_precisely_ what unless is for. it's just a funny way of writing
if(!... or should I say if(! is a funny way to write unless ;-)
But honestly pun aside unless(){} is far more readable than if(!){}
and _especially_ if you are programming in an exception manner as you
correctly point out. Every language should have an unless construct.
[...]
> And you could even force perl to exit with an exit code !=3D 0
> to indicate that something happened (e. g. program wasn't run
> successfully).
>
a good practice in any language...
> Now, as the "don't want case" has been considered, you can
> easily continue with your program, no need to put it into
> an else { } branch.
>
ahh! the clarity of unless
>
>
>
> PS. I'm not familiar with perl enough to be sure that the !
> =A0 =A0operator can be used at @ARGV to make sure it's > 0,
In "scalar context" will automagically return the number of elements
perldoc perlintro (section Perl variable types)
> =A0 =A0and how or if to use exit() to set the return code.
die "Bailing cause you forgot the filename" unless @ARGV
Yes, that _is_ actual code :) Will not only die with a pretty message
on STDERR but will return the value of $! (errno) as exit value. (no
need to make up exit codes) Good thing we are on a FBSD list, because
I can't see the sense of programming in a non-nix environment ;-)
> =A0 =A0I hardly can read perl at all, so the essence of my
> =A0 =A0examples is of a rather generic nature. :-)
Look mommi! Reading Perl is just like reading plain english! (or in
Nigerian spam for that matter
http://search.cpan.org/~jwalt/Acme-Lingua-NIGERIAN-1.0.0/NIGERIAN.pm)
Cheers,
Alejandro Imass
>
> --
> Polytropon
> Magdeburg, Germany
> Happy FreeBSD user since 4.0
> Andra moi ennepe, Mousa, ...
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