From: forgottenwizard <phrexianreaper@...>
Date: 2007-07-30T14:10:31+09:00
Subject: Re: Performance diffrence between ifs and case

On 13:47 Mon 30 Jul     , Francis Cianfrocca wrote:
> On 7/28/07, forgottenwizard <phrexianreaper@hushmail.com> wrote:
> >
> > What kind of diffrences are there, effectivly, between case and a series
> > of if statements, like in this:
> >
> > if i="hi"
> >         puts "hi"
> > elsif i="bye"
> >         puts "bye"
> > else
> >         puts i
> > end
> >
> > and
> >
> > case i
> >         when hi
> >                 puts "hi"
> >         when bye
> >                 puts "bye"
> > else
> >         puts i
> > end
> >
> >
> >
> 
> As you've written the code, the first example will probably run noticeably
> faster because it will never perform a comparison. The assignment in the
> first if statement will always be true, and so the first branch will always
> be taken.
> 
> To answer a related question (but one that you didn't ask): case/when uses
> the === operator rather than  ==, which is typically used in if/when
> constructions that (unlike yours) are intended to perform comparisons rather
> than assignments.
> 
> And perhaps surprisingly, === is extremely slow when applied to arguments
> that are Symbols. In those cases, I always use if/else.

Actually, I'm going by the contents of ARGV[] with the actual program. I
ran across symbols just awhile ago looking through a few refrences, but
havn't messed with them any currently.

A more-or-less realistic example would be (just using case here):

case ARGV[9]
	when "hi", "H"
		puts "hi"
	when "bye, "B"
		puts "bye"
else
	puts ARGV[9]
end

Don't know if that makes a diff, but all this is pretty much passed down
through a single starting function as arguments to the function.