Prime#twins

prime_twins.rb

require 'prime'
class Prime
  def twins n = nil
    return to_enum :twins, n unless block_given?
    each(n).each_cons(2) do |p1, p2|
      yield [p1, p2] if p2 - p1 == 2
    end
  end
end

# Prime.twins.take(10)
# => [[3, 5], [5, 7], [11, 13], [17, 19], [29, 31], [41, 43], [59, 61], [71, 73], [101, 103], [107, 109]]
# Prime.twins(100).to_a
# => [[3, 5], [5, 7], [11, 13], [17, 19], [29, 31], [41, 43], [59, 61], [71, 73]]