;; This file contains excerpts from the textbook Concrete
;; Abstractions: An Introduction to Computer Science Using Scheme, by
;; Max Hailperin, Barbara Kaiser, and Karl Knight, Copyright (c) 1998
;; by Brooks/Cole Publishing Company. This file may not be reproduced
;; or redistributed other than for use with that textbook.

;; From chapter 14:

(define-class
  'item-list
  object-class
  '(item-vector
  num-items)
 '(
   ;; intended for public consumption:
   add
   display
   total-price
   delete
   choose
   empty?
   ;; intended for private, internal use:
   grow
   ))

(class/set-method!
 item-list-class 'init
 (lambda (this)
   (item-list/set-item-vector! this (make-vector 10))
   (item-list/set-num-items! this 0)))

(class/set-method!
 item-list-class 'add
 (lambda (this item)
   (let ((num-items (item-list/get-num-items this))
         (item-vector (item-list/get-item-vector this)))
     (if (= num-items (vector-length item-vector))
         (begin (item-list/grow this)
                (item-list/add this item))
         (begin (vector-set! item-vector num-items item)
                (item-list/set-num-items! this (+ num-items 1))
                'added)))))

(define-class
  'item
  object-class
  '(price)
  '(
    ;; intended for public consumption:
    price
    display
    input-specifics
    revise-specifics))

(class/set-method!
 item-class 'init
 (lambda (this price)
   (item/set-price! this price)))

;; From chapter 13:

(define from-to-do
  (lambda (start stop body)
    (if (> start stop)
        'done
        (begin (body start)
               (from-to-do (+ 1 start) stop body)))))

;; Partial solution to exercise 14.8:

(class/set-method!
 item-class 'price
 (lambda (this)
   (item/get-price this)))