Prime#sexy_pair

prime_sexy.rb

require 'prime'

class Prime
  def sexy_pair n = nil
    return to_enum :sexy_pair, n unless block_given?
    each(n).each_cons(3) do |p1, p2, p3|
      yield [p1, p2] if p2 - p1 == 6
      yield [p1, p3] if p3 - p1 == 6
    end
  end

  def sexy_triplets n = nil
    return to_enum :sexy_triplets, n unless block_given?
    sexy_hash = {}
    sexy_pair(n) do |p1, p2|
      sexy_hash[p2] = true
      if sexy_hash[p1] && !(p2 + 6).prime?
        yield [p1 - 6, p1, p2]
      end
    end
  end

  def sexy_quadruplets n = nil
    return to_enum :sexy_quadruplets, n unless block_given?
    sexy_hash = {}
    sexy_pair(n) do |p1, p2|
      sexy_hash[p2] = true
      if sexy_hash[p1 - 6]
        yield [p1 - 12, p1 - 6, p1, p2]
      end
    end
  end
end