Re-implementing the iterators

my_impl.rb

class Array
  def my_map(&nameless_fn)
    new_arr = []
    return Enumerator.new(self, :my_map) unless nameless_fn
    self.each do |x|
      new_arr << nameless_fn.call(x)
    end
    new_arr
  end

  def my_map!(&nameless_fn)
    return Enumerator.new(self, :my_map!) unless nameless_fn
    self.each_with_index do |x, i|
      self[i] = nameless_fn.call(x)
    end
  end

  def my_select(&nameless_fn)
    new_arr = []
    self.each do |x|
      new_arr << x if nameless_fn.call(x)
    end
    new_arr
  end
end