From: Martin DeMello <martindemello@...>
Date: 2003-05-30T05:42:57+09:00
Subject: Re: Iteration - last detection

Orion Hunter <orion2480@hotmail.com> wrote:
> Is there any built in functionality for iteration that will allow me to 
> detect when I am on the last element?  This would not be hard for an Array, 
> using array.length, but what about a Hash?  How would I know when I am at 
> the last element?

Not built in, but this should work:

module Enumerable
  def each_with_lastp # no shortage of nicer names, I'm sure :)
    flag = nil
    i = nil
    each {|j|
      yield [i, false] if flag
      i = j
      flag = true
    }
    yield [i,true]
  end
end

a = [1,2,3,4,5,6,7,8,9]
a.each_with_lastp {|i, last|
  print i
  print last ? "" : ","
}

It's rather crude, in that there's the overhead of a call to 'if flag'
with every iteration, but I couldn't think of a way around that.

martin