From: dblack@...
Date: 2003-05-30T07:58:35+09:00
Subject: Re: Iteration - last detection

On Fri, 30 May 2003, ahoward wrote:

> module Enumerable
>   def each_with_last(&block)
>     l = nil
>     each_with_index do |e, i|
>       block.call l, false if i > 0
>       l = e
>     end
>     block.call l, true
>   end
> end

OK, as penance for clouding the issue with the mythical
Enumerable#size, I feel morally obliged to write a real version :-)
I'm not sure how horrible this is.  Very, I suspect.  But anyway,
another possibility:

  module Enumerable
    def each_with_last
      n = -1
      each { n += 1 }
      each_with_index {|e,i| yield(e, i == n)}
    end
  end

It benchmarks a bit faster than yours, for arrays of size 10 to 10000,
but not wildly so.


David

-- 
David Alan Black
home: dblack@superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav