From: Michael Fellinger <m.fellinger@...>
Date: 2007-03-27T09:39:59+09:00
Subject: Re: Question about if in Ruby

i have used that yet another way:

this or that if foo

but it depens on the return-value...

On 3/24/07, Trans <transfire@gmail.com> wrote:
>
>
> On Mar 23, 7:53 am, Vince H&K <vince.h...@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.
>
>
> There is one other difference.
>
>   if a = 1
>     p a
>   end
>
>   p a if a = 1
>
> The later does not assign the a.
>
> btw you can also use parens for more than one call.
>
>
>   ( do_this ; do_that ) if something
>
> or
>
>   ( do_this
>     do_that
>   ) if something
>
>
> T.
>
>
>