From: "David A. Black" <dblack@...>
Date: 2007-03-23T21:59:21+09:00
Subject: Re: Question about if in Ruby

Hi --

On 3/23/07, Vince H&K <vince.hetk@gmail.com> wrote:
> John Joyce wrote:
> > I've seen this in Rails, but it is just ERb, so it is Ruby...
> >
> >
> > <%= link_to 'Previous page', { :page => @product_pages.current.previous
> > } if @product_pages.current.previous %>
> >
> >
> > I'm curious how it is different from this...
> >
> >
> > <%=  if @product_pages.current.previous link_to ('Previous page', {
> > :page => @product_pages.current.previous })
> >     end
> >  %>
> >
> >
> > I've seen this kind of if statement reversal a few times now in Ruby
> > code. I call it do-if because it looks similar to do-while, but I am
> > curious if reversing the condition affects the interpreter's speed at
> > all. If they are the same, then isn't the standard if conditional better
> > for human legibility and understanding?
>
>   The first form of the statement is valid for only one instruction. Both
>
> if something
>   do_something
> end
>
> and
>
> do_something if something
>
> are equivalent, but when it comes to
>
> if a
>   one_thing
>   another_thing
> end
>
> you simply can't use the other form, as it applies to only one instruction.

Just for completeness (I'm not recommending it), I'll mention that you can do:

  one_thing if begin
                      another_thing
                      a_third_thing
                    end


David

-- 
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