One of each item from an array of arrays.

feed_me.rb

require "./one_of_each"

meats = %w(steak carnitas chicken barbacoa)
beans = %w(no pinto black)
salsas = %w(no mild medium hot nuclear)
guacamoles = [true,false]
rices = [true,false]
sour_creams = [true,false]
cheeses = [true,false]
lettuces = [true,false]

ingredients = [meats, beans, salsas, guacamoles, rices, sour_creams, cheeses, lettuces]


ingredients.one_of_each(ingredients, []) do |i|
	p i.join " "
end

one_of_each.rb

BEGIN {

class Array
	def one_of_each (lists, elements, &block)
		if lists.size == 1
			lists[0].each do |item|
				elements.push item
				yield elements
				elements.pop
			end
		elsif lists.size > 1
			list = lists.pop
			list.each do |item|
				elements.push item
				one_of_each(lists, elements, &block)
				elements.pop
			end
			lists.push list
		end
	end
end
}

original_burritos.rb

beans = %w(no pinto black)
salsas = %w(no mild medium hot nuclear)
guacamoles = [true,false]
rices = [true,false]
sour_creams = [true,false]
cheeses = [true,false]
lettuces = [true,false]

burritos = []

meats.each do |meat|
	beans.each do |bean|
		salsas.each do |salsa|
			guacamoles.each do |guac|
				rices.each do |rice|
					sour_creams.each do |sour|
						cheeses.each do |cheese|
							lettuces.each do |lettuce|
								burrito = "#{meat} burrito with #{bean} beans"
								burrito += rice ? ", rice" : ""
								burrito += guac ? ", guacamole" : ""
								burrito += sour ? ", sour cream" : ""
								burrito += lettuce ? ", lettuce" : ""
								burrito += cheese ? ", cheese" : ""
								burrito += ", and #{salsa} salsa"
								burritos.push burrito
							end
						end
					end
				end
			end
		end
	end
end

puts burritos
puts burritos.count

Rakefile

require 'rake/testtask'

Rake::TestTask.new do |t|
  t.libs << "test"
  t.test_files = FileList['test*.rb']
  t.verbose = true
end

test_one_of_each.rb

require "./one_of_each"
require "test/unit"
 
class TestOneOfEach < Test::Unit::TestCase
 
  def setup
    beans = %w(no pinto black)
    salsas = %w(no mild medium hot nuclear)
    guacamoles = [true,false]
    rices = [true,false]
    sour_creams = [true,false]
    cheeses = [true,false]
    lettuces = [true,false]

    @burritos = []
  end
 
  def teardown
    ## Nothing really
  end
 
  def test_simple
    assert_equal(4, 4)
  end
 
  def test_simple2
    assert_equal(4, 4)
  end
 
end