From: Chad Perrin <perrin@...>
Date: 2007-03-15T12:20:19+09:00
Subject: Re: Newbie: if / elseif

On Thu, Mar 15, 2007 at 12:12:17PM +0900, Augie De Blieck Jr. wrote:
> >if $val =~ /this/i
> >  puts "this"
> >elseif $val =~ /that/i
> >  puts "that"
> >elseif $val =~ /the other/i
> >  puts "the other"
> >end
> 
> Just remember that even when you spell it right, it's going to drop
> out of the whole construct just as soon as it fulfills a RegEx.  After
> it prints "this," it stops looking at any of the other "elsif"
> statements.
> 
> That short circuiting is a feature. =)

Indeed -- that's the whole point of using elsif rather than just a list
of separate if statements.  The if/elsif/else construct is used for
mutually exclusive flow control, where only one of several is to be
executed.  Using a series of if statements considers each in a vacuum,
in order, while if/elsif/else considers them all as part of a greater
whole.

-- 
CCD CopyWrite Chad Perrin [ http://ccd.apotheon.org ]
"Real ugliness is not harsh-looking syntax, but having to
build programs out of the wrong concepts." - Paul Graham