From: Robert <bob.news@...>
Date: 2003-05-31T18:56:47+09:00
Subject: Re: Iteration - last detection

Great solution.  Thank's for showing how simple some things become if you
look at them from the right perspective.

    robert

"Brian Candler" <B.Candler@pobox.com> schrieb im Newsbeitrag
news:20030530123215.GA8185@uk.tiscali.com...
> On Fri, May 30, 2003 at 08:33:15PM +0900, Carlos wrote:
> > > Is there any built in functionality for iteration that will allow me
to
> > > detect when I am on the last element?
> ..
> > Here is a module that implements it, but you should include it in every
> > class where you want #each to behave that way :-/.
> ..
> > def EachWithLast.append_features(klass)
> > old_each="each_"+rand(10000).to_s+Time.now.usec.to_s
> > klass.class_eval <<-FINISH
>
> Err??!
>
> I must be missing something; why is this not an incredibly simple thing to
> achieve?
>
> module Enumerable
>   def each_with_last
>     prev = nil
>     each_with_index do |item,index|
>       yield prev,false if index > 0
>       prev = item
>     end
>     yield prev,true
>   end
> end
>
> irb(main):011:0> [1,2,3,4,5].each_with_last do |a,b| puts a,b; end
> 1
> false
> 2
> false
> 3
> false
> 4
> false
> 5
> true
>
> It was Nobu's comment that this should work with IO which made me think it
> must work this way: you simply keep reading items until there are no more
> (eof in the case of IO), and then you yield with 'true' for the last one.
>
> But like I say, I might have missed something...
>
> Regards,
>
> Brian.
>