From: Xavier Noria <fxn@...>
Date: 2009-07-29T17:50:31+09:00
Subject: Re: previous value in array block

each_cons seems natural here:

require 'enumerator'

a = [1, 3, 3, 2]
b = a[0, 1]

a.each_cons(2) { |x, y| b << y - x }