Caesar cypher for Ruby

caesar_cypher.rb

class String
  def to_caesar shift
    shift = (shift % 26).abs
    each_byte.map { |b| ((b + shift - 97) % 26 + 97).chr }.join
  end
end

a = "Caesar was a cool guy"

p a.split.map { |w| w.to_caesar 4 }.join(' ') # => "aeiwev aew e gssp kyc"