95 lines
3.6 KiB
Plaintext
95 lines
3.6 KiB
Plaintext
;;;;
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;;;; E x a m p l e 0 . s t k
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;;;;
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;;;; Copyright © 1994-1999 Erick Gallesio - I3S-CNRS/ESSI <eg@unice.fr>
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;;;;
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;;;; Permission to use, copy, modify, distribute,and license this
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;;;; software and its documentation for any purpose is hereby granted,
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;;;; provided that existing copyright notices are retained in all
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;;;; copies and that this notice is included verbatim in any
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;;;; distributions. No written agreement, license, or royalty fee is
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;;;; required for any of the authorized uses.
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;;;; This software is provided ``AS IS'' without express or implied
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;;;; warranty.
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;;;;
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;;;; Author: Erick Gallesio [eg@kaolin.unice.fr]
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;;;; Creation date: 5-Aug-1994 10:30
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;;;; Last file update: 3-Sep-1999 20:08 (eg)
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;;;; This file desmonstates the use of composite objects. First we define the class
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;;;; <Car> and <Caravan>.
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(define-class <Car> ()
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((power :init-keyword :power :accessor power)
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(driver :init-keyword :driver :accessor driver)
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(color :init-keyword :color :accessor color)))
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(define-class <Caravan> ()
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((capacity :init-keyword :capacity :accessor capacity)
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(color :init-keyword :color :accessor color)))
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;;;; Hereafter is a first definition of <Camping-car>. Note that the color slot
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;;;; is propagated to the color slot of the "house" and "car" components of the
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;;;; camping car. Note the use of the :metaclass option for managing :propagated
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;;;; slots.
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(define-class <Camping-car>()
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((car :getter car-of) ;; Don't redefine CAR!!!!
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(house :getter house)
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(color :init-keyword :color :accessor color
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:allocation :propagated :propagate-to (car house)))
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:metaclass <Composite-metaclass>)
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;;;; Defining a composite widget requires to define a initialize method.
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(define-method initialize ((self <Camping-car>) initargs)
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(slot-set! self 'car (make <Car>))
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(slot-set! self 'house (make <Caravan>))
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(next-method))
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;;;; And now we can define a camping-car
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(define cc (make <Camping-car> :color "red"))
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(color cc) ; ===> "red"
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(color (car-of cc)) ; ===> "red"
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(color (house cc)) ; ===> "red"
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(slot-set! cc 'color "yellow") ; other writing: (set! (color cc) "yellow")
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(color cc) ; ===> "yellow"
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(color (car-of cc)) ; ===> "yellow"
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(color (house cc)) ; ===> "yellow"
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;;;; Of course, color of the house coud be different and we can do
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(set! (color (house cc)) "green")
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(color cc) ; ===> "yellow"
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(color (car-of cc)) ; ===> "yellow"
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(color (house cc)) ; ===> "green"
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;;;; Getting or setting the power of the car with this first definition
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;;;; is a little bit messy. We have to do
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;;;; (set! (power (car-of cc)) 10)
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;;;; To avoid this we can use a "power" propagated slot which will propagate
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;;;; to the "car" component. Another way consists to use inheritance.
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;;;;
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;;;; Note: Purists will tell you that inheritance permits object specialization
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;;;; and NOT object composition. However, we can use it here to avoid the
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;;;; definition of propagated slots.
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;;;;
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;;;; Here is the new definition of <Camping-car>.
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(define-class <Camping-car>(<Car>)
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((car :getter car-of) ;; Don't redefine CAR!!!!
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(house :getter house)
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(color :init-keyword :color :accessor color
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:allocation :propagated :propagate-to (car house)))
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:metaclass <Composite-metaclass>)
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;;;; initialize is unmodified (but we have to redefine it since <Camping-car>
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;;;; was changed.
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(define-method initialize ((self <Camping-car>) initargs)
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(slot-set! self 'car (make <Car>))
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(slot-set! self 'house (make <Caravan>))
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(next-method))
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;;;; Now we can do
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(define cc2 (make <Camping-Car> :color "brown" :driver "Joe" :power 10))
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