;; 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.

;; Chapter 14: Object-Oriented Programming

;; 14.5  An Application: Adventures in the Imaginary Land of Gack

(define-class
  'registry
  object-class
  '(list)
  '(add
    remove
    trigger
    trigger-times))

(class/set-method!
 registry-class 'init
 (lambda (this)
   (object^init this)
   (registry/set-list! this '())))

(class/set-method!
 registry-class 'add
 (lambda (this person)
   (registry/set-list! this
                       (cons person
                             (registry/get-list this)))))

(class/set-method!
 registry-class 'remove
 (lambda (this person)
   (registry/set-list! this
                       (delq person
                             (registry/get-list this)))))

(class/set-method!
 registry-class 'trigger
 (lambda (this)
   (for-each auto-person/maybe-act
             (registry/get-list this))))

(class/set-method!
 registry-class 'trigger-times
 (lambda (this n)
   (if (> n 0)
       (begin (registry/trigger this)
              (registry/trigger-times this (- n 1)))
       'done)))