From: John W Higgins <wishdev@...>
Date: 2009-06-12T02:18:31+09:00
Subject: Re: Idiomatic way to detect first/last iteration?

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On Thu, Jun 11, 2009 at 9:43 AM, Kendall Gifford <zettabyte@gmail.com>wrote:

> 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.
>
>
One option (not necessarily much prettier) would be to explicitly select out
the portions

genres = %w{ classical punk rock jazz }
puts "My absolute favorite #{genres[0]}"
genres[1..-2].each{ |g| puts "Another favorite #{g}" }
puts "My least favorite #{genres[-1]}" unless genres.length == 1

John

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