From: Max Muermann <ruby@...>
Date: 2006-08-09T11:18:10+09:00
Subject: Re: Simple looping question

equire 'yaml'
require 'enumerator'

data = YAML::load File.read('data.yml')
data.entries.sort_by{|date, *| date }.each_cons(2) do  | first, second |
 date_first = DateTime.parse(second[0].to_s)
 date_second = DateTime.parse(first[0].to_s)
 duration = date_first - date_second
 miles = second[1][1] - first[1][1]
 miles_per_gallon = miles / first[1][0]
 p "The #{first[1][0]} gallons of gas purchased on
#{date_first.strftime('%m/%d/%Y')} lasted #{duration.to_i} days. The
mileage was #{miles_per_gallon} miles per gallon."
end

The key here is the each_cons coming from the enumerable mixin, which
iterates the array in pairs of twos.

Disclaimer: I am a German living in Australia, so if I got the date
format or the miles per gallon calculation wrong, blame the non-metric
system.

Max