enum with select to return custom collection

cool_enum.rb

class CoolCollection
  include Enumerable
  def initialize
    @elements = []
  end
  def <<(elem)
    @elements << elem
  end
  def each &block
    @elements.each do |elem|
      if block_given?
        block.call elem
      else
        yield elem
      end
    end
  end
  
  def select &block
    selection = @elements.select do |elem|
      if block_given?
        block.call elem
      else
        yield elem
      end
    end
    output = self.class.new
    selection.each do |elem|
      output << elem
    end
    output
  end
end

my_coll = CoolCollection.new
my_coll << 7
my_coll << 9
p my_coll
#=> #<CoolCollection:0x25cad78 @elements=[7, 9]>
my_coll.each {|elem| puts elem}
selection = my_coll.select {|elem| elem == 7}
p selection
#<CoolCollection:0x25c9e48 @elements=[7]>