Scheme's cons, car, and cdr in Ruby

cons_car_cdr.rb

# A possible implementation of
# Scheme's cons, car, and cdr in Ruby
def cons x, y
  lambda do |pick|
    case pick
    when 1; x
    when 2; y
    end
  end
end

def car pair
  pair.call 1
end

def cdr pair
  pair.call 2
end

ex = (cons 3, (cons 4, (cons 5, 6)))

p (car (cdr (cdr ex)))