From: Gary Wright <gwtmp01@...>
Date: 2007-04-03T15:31:09+09:00
Subject: Re: Last iteration condition


On Apr 3, 2007, at 1:44 AM, Brian Candler wrote:
> Try thread around
> http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/72518
> for some sample implementations.

Building off of Brian's suggestion in that thread, here
is a way to provide a 'countdown' as the end of the iteration
approaches.  Default is to only flag the last item but you
can ask for any number of items to be flagged.

This is the first time I've found a need for the numeric return
value of nonzero?

module Enumerable
def each_with_countdown(count=0)
    queue = []
    each_with_index do |item,index|
      if index > (count)
       yield queue.shift, true
     end
     queue.push(item)
    end
    queue.each_with_index do |item, index|
      yield item, (count - index).nonzero?
    end
end
end

[1,2,3,4,5,6].each_with_countdown(3) { |item, more|
   case more
   when TrueClass
     puts "#{item}"
   when 3
     puts "#{item}, next to next to next to last item!"
   when 2
     puts "#{item}, next to next to last item!"
   when 1
     puts "#{item}, next to last item!"
   when NilClass
     puts "#{item}, last item"
   end
}

[1,2,3,4,5,6].each_with_countdown(1) { |item, more|
   puts "#{item}, more: #{more.inspect}"
}

[1].each_with_countdown { |item, more|
   puts "#{item}, more: #{more.inspect}"
}

StringIO.new("line1\nline2\nline3").each_with_countdown do |line, more|
   if more
     puts line
   else
     puts "last: #{line}"
   end
end


Gary Wright