From: Kendall Gifford <zettabyte@...>
Date: 2009-06-12T01:43:16+09:00
Subject: Idiomatic way to detect first/last iteration?

Hi there, is there any recognized ruby idiomatic way for detecting
when you're on the first and/or last iteration over a collection? Or,
if not, anyone know of any tricky ways?

Specifically, I'm trying to avoid using each_with_index (as shown
below):

genres = %w{ classical punk rock jazz }
genres.each_with_index do |genre, i|
  desc = "one of my favorites"
  desc = "my absolute favorite" if i.zero?
  desc = "my least fav. of all my favorites" if i + 1 == genres.length
  puts "#{genre} is #{desc}"
end

I just don't like having to compare an index value (especially as when
detecting the final iteration) and hate even having it as a loop
parameter unless absolutely necessary. I know, I'm picky. Just wanted
to beat the bushes and see if any cool alternatives pop up.