From: Peter Ertl <pertl@...>
Date: 2006-03-24T23:52:37+09:00
Subject: Re: iterator class not working

Indeed, you topped my solution my needing one callcc less...

I allowed myself to change it a little so it will return 
nil once the enumeration is done and does not need exceptions:

class Iterator
  def initialize( enum )
    @enum = enum
    @next = nil
  end

  def next
    @next.call if @next
    @enum.each do |item|
      callcc do |cc|
        @next = cc
        return item
      end
    end
    nil
  end
end

i = Iterator.new( %w{ Ringo John Paul George } )

while item = i.next
  puts item
end


> --- Urspr�ngliche Nachricht ---
> Von: "Robert Dober" <robert.dober@gmail.com>
> An: ruby-talk@ruby-lang.org (ruby-talk ML)
> Betreff: Re: iterator class not working
> Datum: Fri, 24 Mar 2006 23:43:15 +0900
> 
> On 3/24/06, Ross Bamford <rossrt@roscopeco.co.uk> wrote:
> >
> > Just a small fix:
> >
> > On Fri, 2006-03-24 at 22:49 +0900, Ross Bamford wrote:
> > >   def initialize(enum)
> > >     @yield = lambda do
> > >       enum.each do |item|
> > > -       @yield = callcc { |cc|
> >   +       callcc { |cc|
> > >           @next.call cc, item
> > >         }
> > >       end
> > >       raise "Exhausted"
> > >     end
> > >   end
> >
> > Doesn't really hurt (as currently written) but it's unnecessary and
> > could cause confusion.
> >
> > --
> > Ross Bamford - rosco@roscopeco.REMOVE.co.uk
> 
> 
> Well I got it!
> Was I missing something or is my solution really better?
> 
> ---------------------------------- 8< --------------------------
> class Iterator
>     class Exhausted < Exception; end
>     def initialize( enum )
>         @enum = enum
>         @next = nil
>     end
> 
>     def next
>         return @next.call if @next
>         @enum.each do
>             |item|
>             callcc{ |cc|
>                 @next = cc
>                 return item
>             }
>         end # do
>         raise Exhausted, "No more items :("
>     end # def next
> end # class Iterator
> 
> i = Iterator.new( %w{ Ringo John Paul George } )
> loop do; puts i.next; end
> 
> 
> 
> 
> 
> --
> Deux choses sont infinies : l'univers et la b�tise humaine ; en ce qui
> concerne l'univers, je n'en ai pas acquis la certitude absolue.
> 
> - Albert Einstein
>