From: Francis Cianfrocca <garbagecat10@...>
Date: 2007-07-30T13:47:27+09:00
Subject: Re: Performance diffrence between ifs and case

------=_Part_30567_4071104.1185770850466
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Content-Disposition: inline

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.

------=_Part_30567_4071104.1185770850466--