Technical Question

rot.rb

def rotx(x, string, encrypt=true)
  alphabet = Array("A".."Z") + Array("a".."z")
  results = []

  if encrypt == true
    key_encrypt_true = Hash[alphabet.zip(alphabet.rotate(x))]
    string.chars.each do |i|
      if ('a'..'z').include? i
        results << key_encrypt_true.fetch(i).downcase
      elsif ('A'..'Z').include? i
        results << key_encrypt_true.fetch(i).upcase
      else
        results << i
      end
    end
    return results.join
  else
    key_encrypt_false = Hash[alphabet.zip(alphabet.rotate(26 - x))]
    string.chars.each do |i|
      if ('a'..'z').include? i
        results << key_encrypt_false.fetch(i).downcase
      elsif ('A'..'Z').include? i
        results << key_encrypt_false.fetch(i).upcase
      else
        results << i
      end
    end
    return results.join
  end
end

raise "You shall not pass!" if not rotx(10, "Hello, World") == "Rovvy, Gybvn"
raise "You shall not pass!" if not rotx(10, "Rovvy, Gybvn", false) == "Hello, World"
raise "You shall not pass!" if not rotx(36, "Hello, World") == "Rovvy, Gybvn"