Ruby rot13

rot13.rb

# or simply:
'foobar'.tr 'A-Za-z','N-ZA-Mn-za-m'


# rot(x)
class String
  def rot(num = 13)
    return self.split('').collect do|ch|
      if /^[a-z]$/ === ch
        ((ch.ord + num - 'a'.ord) % 26 + 'a'.ord).chr
      elsif /^[A-Z]$/ === ch
        ((ch.ord + num - 'A'.ord) % 26 + 'A'.ord).chr
      else
        ch
      end
    end.join('')
  end

  alias rot13 rot
end


# Example usage
p 'fefe'.rot(10)