def compact
      filter("compact") do |yielder|
        each do |element|
          yielder.call(element) unless element.nil?
        end
      end
    end
def compact
      filter("compact") do |yielder|
        each do |element|
          yielder.call(element) unless element.nil?
        end
      end
    end
Ignore nil values.

 @return [Enumerable] the elements that are not nil

 @see ::Array#compact