From: Rick DeNatale <rick.denatale@...>
Date: 2007-05-01T05:10:29+09:00
Subject: Re: cyclic array

On 4/30/07, Xavier Noria <fxn@hashref.com> wrote:
> On Apr 30, 2007, at 3:43 AM, Rick DeNatale wrote:
>
> > On 4/28/07, Xavier Noria <fxn@hashref.com> wrote:
> >
> >>
> >> This is a possible approach:
> >>
> >>    module Enumerable
> >>      def each_cycle(window, start=0)
> >>        (start...length+start).each do |i|
> >>          yield((i..i+window).map {|n| self[n % length]})
> >>        end
> >>      end
> >>    end
> >
> > This method won't work for Enumerables in general, although I guess it
> > does work for Arrays.
> >
> > Not all enumerables have one or both length or [] methods.
>
> Oh right, thank you. I don't know why ri Enumerable lists length
> here, looks like it is getting non-core methods from somewhere else.
> I overlooked [] though. The OP wanted this for an Array, it would
> certainly work there.

By the way I think that there's a typo that should be an open range in
the yield expression, otherwise you get

     yield((i...i+window).map {|n| self[n % length]})

Thinking about the Enumerable vs. Array aspect of this got me thinking
abou the subtleties of duck typing leading to another blog entry:

http://talklikeaduck.denhaven2.com/articles/2007/04/30/our-kind-of-ducks-odd-ducks-and-trained-ducks


-- 
Rick DeNatale

My blog on Ruby
http://talklikeaduck.denhaven2.com/