79 lines
2.8 KiB
Scheme
79 lines
2.8 KiB
Scheme
;;; Copyright (C) Peter McGoron 2024
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;;; This program is free software: you can redistribute it and/or modify
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;;; it under the terms of the GNU General Public License as published by
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;;; the Free Software Foundation, version 3 of the License.
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;;;
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;;; This program is distributed in the hope that it will be useful,
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;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;;; GNU General Public License for more details.
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;;;
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;;; You should have received a copy of the GNU General Public License
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;;; along with this program. If not, see <https://www.gnu.org/licenses/>.
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;;;
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;;; Create a new object.
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;;;
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;;; Messages:
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;;; (SET! KEY VAL): Set KEY in the table to VAL.
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;;; (GET KEY): Get value of KEY in table.
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;;; (ADD-TYPE TYPE): Add TYPE to the list of types of the object.
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;;; (OF-TYPE? TYPE): Check if object has TYPE in the type list.
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;;;
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;;; Attributes:
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;;; TYPES: List of types associated with the object.
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(define object
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(lambda ()
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(let ((table (symbol-table)))
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(table 'set! 'set! (lambda (key val) (table 'set! key val)))
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(table 'set! 'get (lambda (key) (table 'get key)))
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(table 'set! 'delete! (lambda (key) (table 'delete! key)))
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(table 'set! 'types '(object))
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(table 'set! 'add-type (lambda (type)
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(table 'set! 'type
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(cons type (table 'get 'types)))))
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(table 'set! 'of-type? (lambda (type)
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(memq type (table 'get 'types))))
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(let ((must-execute-default
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(lambda (op args)
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(let ((proc (table 'get 'default)))
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(if (not proc)
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(error 'object 'invalid-op op args)
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(apply proc args))))))
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(lambda (op . args)
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(let ((proc (table 'get op)))
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(if (not proc)
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(must-execute-default op args)
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(apply proc args))))))))
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;;; (OBJECT/ATTRIBUTES NAME1 VAL1 NAME2 VAL2 ...)
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;;; creates a new object with NAME1 bound to VAL1, NAME2 bound to VAL2,
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;;; etc.
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(define object/attributes
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(lambda args
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(let ((obj (object)))
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(letrec ((process-args
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(lambda (name val . rest)
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(obj 'set! name val)
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(apply check-args rest)))
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(check-args
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(lambda args
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(if (null? args)
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obj
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(apply process-args args)))))
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(apply check-args args)))))
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(define object-make-abstract!
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(lambda (obj)
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(obj 'delete! 'set!)
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(obj 'delete! 'get)
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(obj 'delete! 'delete!)
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obj))
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;;; Like OBJECT/ATTRIBUTES, but with SET!, GET, and DELETE! removed.
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(define object/abstract
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(lambda args
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(object-make-abstract! (apply object/attributes args))))
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