From: Drew Olson <olsonas@...>
Date: 2007-08-09T04:05:26+09:00
Subject: Re: Iterating list in pairs

FireAphis wrote:
> Hello,
> 
> I need to iterate through a list and handle two elements on every
> iteration. That is I'd like to do something like

Weird, I just blogged about this topic: http://drewolson.wordpress.com/.

I did it using the zip method, something like this (I added block 
handling to this example):

class Array
  def adjacent_pairs
    if block_given?
      self[0..-2].zip(self[1..-1]).each do |a,b|
        yield a,b
      end
    else
      self[0..-2].zip(self[1..-1])
    end
  end
end

Now we can do either of the following:

irb(main):012:0> [1,2,3,4].adjacent_pairs
=> [[1, 2], [2, 3], [3, 4]]
irb(main):013:0> [1,2,3,4].adjacent_pairs do |a,b|
irb(main):014:1*   puts "#{a} #{b}"
irb(main):015:1> end
1 2
2 3
3 4
=> [[1, 2], [2, 3], [3, 4]]
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