Newtype on Ruby

new_type.rb

class Class
  def new_type(&block)
    new_class = self.dup
    new_class.class_eval(&block) if block_given?
    new_class
  end
end

CArray = Array.new_type do
  def example
    sample
  end
end

cary = CArray.new(10){ rand(10) }
p cary.example