Method: (RUCKSACK-ROOTS STANDARD-RUCKSACK)

Source

(defmethod rucksack-roots ((rucksack standard-rucksack))
  (let ((result '()))
    (map-rucksack-roots (lambda (root) (push root result))
                        rucksack)
    ;; We don't need to nreverse the list, because the order isn't specified.
    result))