From: Andreas Ericsson <ae@op5.se>
Date: Sun, 08 Jan 2006 00:07:25 GMT
Subject: Re: [PATCH] git-mv.perl: use stderr for error output and cleanup
Message-ID: <43C057BD.7010201@op5.se>
In-Reply-To: <7v7j9bg369.fsf@assigned-by-dhcp.cox.net>

Junio C Hamano wrote:
> 
> BTW, I never understood the usefulness of Statement Modifiers.
> Even reading the examples in perlsyn.pod:
> 
>     print "Basset hounds got long ears" if length $ear >= 10;
>     go_outside() and play() unless $is_raining;
> 
> seeing "do these things" upfront and then realize "ah, but that
> is done only when this holds true", interrupts the flow of
> understanding while reading a program by somebody else [*1*].


Here's what "Programming Perl" by O'Reilly (third edition, somewhere 
around page 604) has to say about it:
---%<---%<---%<---
*) Do things the most readable way. For instance:

     open(FOO, $foo) or die "Can't open $foo: $!";

is  better than

     die "Can't open $foo: $!" unless open(FOO, $foo);

because the second way hides the main point of the statement in a modifier.
---%<---%<---%<---

Considering the book was co-authored by Larry Wall, I'd say that's as 
good as an apology.


> It is worse if the Statement Modifier is a loop control.
> 
> (flamebait) Compound Statements take BLOCK and people who want
> to do a one-liner could not do so without braces.  I've always
> thought Statement Modifies as a lame workaround for that
> problem.
> 

Most things can be done without braces, so long as one doesn't spell out 
the 'if'.

	$opt_h and usage();
	-d $directory or mkdir($directory);

is perfectly valid perl. This way of writing it is familiar enough for 
shell-scripters. Hardcore C-programmers will look twice when they see a 
line that so obviously looks completely wrong and will almost certainly, 
with some revulsion, understand it.

-- 
Andreas Ericsson                   andreas.ericsson@op5.se
OP5 AB                             www.op5.se
Tel: +46 8-230225                  Fax: +46 8-230231