Implementation of Array#transpose

array_transpose.rb

require 'test/unit'
include Test::Unit::Assertions

class Array
  def transpose
    return [] if empty?
    a = Array.new(self.first.size) {[]}
    
    each do |e|
      begin
        e.each_index { |j| a[j].push e[j] || nil }
      rescue NoMethodError
        raise "Element size differs: #{e.size} ? #{a.size}"
      end
    end
    
    a
  end
end

assert_equal [[1, 2, 3], [:a, :b, :c]].transpose, [[1, :a], [2, :b], [3, :c]]
assert_equal [[1,2], [3,4], [5,6]].transpose, [[1, 3, 5], [2, 4, 6]]
assert_equal [].transpose, []