From: Martin DeMello <martindemello@...>
Date: 2004-08-11T05:26:13+09:00
Subject: Re: empty? and size in Enumerable

Robert Klemme <bob.news@gmx.net> wrote:
> "Martin DeMello" <martindemello@yahoo.com> schrieb im Newsbeitrag
> >
> > Can empty? be reliably implemented in terms of each for every
> > enumerable? I can't think of an obvious problem with it, but that
> > doesn't mean there isn't one.
> 
> Yes, that's possible IMHO.  My suggestion would be:
> 
> module Enumerable
>   # O(1)
>   def empty?
>     each { return false }
>     true
>   end

My concern was if #each created a temporary data structure in O(n) time
(e.g. an ordered hash) - this would make sense for #each, since its
running time is O(n) anyway, but would be a large hit for empty?

martin