jackblack.rb

class Card
  attr_reader :value

  def initialize rank
    @rank = rank
    @value = case rank
             when ?A then 11
             when /[TJQK]/ then 10
             else rank.to_i
             end
  end

  def ace?
    @rank == ?A
  end
end

class Hand
  def initialize *cards
    @cards = cards.map(&Card.method(:new))
  end

  def << card
    @cards << card
  end

  def value
    val = @cards.map(&:value).reduce(:+)
    val -= 10 * @cards.count(&:ace?) if val > 21
    val
  end
end

h = Hand.new
h << Card.new(?A)
h << Card.new(?K)

p h.value
h << Card.new(?A)
p h.value

p Hand.new(?Q, ?Q).value