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;;; "object.scm" Macroless Object System
;;;From: whumeniu@datap.ca (Wade Humeniuk)
;;;Date: February 15, 1994
;; Object Construction:
;; 0 1 2 3 4
;; #(object-tag get-method make-method! unmake-method! get-all-methods)
(define object:tag "object")
;;; This might be better done using COMLIST:DELETE-IF.
(define (object:removeq obj alist)
(if (null? alist)
alist
(if (eq? (caar alist) obj)
(cdr alist)
(cons (car alist) (object:removeq obj (cdr alist))))))
(define (get-all-methods obj)
(if (object? obj)
((vector-ref obj 4))
(slib:error "Cannot get methods on non-object: " obj)))
(define (object? obj)
(and (vector? obj)
(eq? object:tag (vector-ref obj 0))))
(define (make-method! obj generic-method method)
(if (object? obj)
(if (procedure? method)
(begin
((vector-ref obj 2) generic-method method)
method)
(slib:error "Method must be a procedure: " method))
(slib:error "Cannot make method on non-object: " obj)))
(define (get-method obj generic-method)
(if (object? obj)
((vector-ref obj 1) generic-method)
(slib:error "Cannot get method on non-object: " obj)))
(define (unmake-method! obj generic-method)
(if (object? obj)
((vector-ref obj 3) generic-method)
(slib:error "Cannot unmake method on non-object: " obj)))
(define (make-predicate! obj generic-predicate)
(if (object? obj)
((vector-ref obj 2) generic-predicate (lambda (self) #t))
(slib:error "Cannot make predicate on non-object: " obj)))
(define (make-generic-method . exception-procedure)
(define generic-method
(lambda (obj . operands)
(if (object? obj)
(let ((object-method ((vector-ref obj 1) generic-method)))
(if object-method
(apply object-method (cons obj operands))
(slib:error "Method not supported: " obj)))
(apply exception-procedure (cons obj operands)))))
(if (not (null? exception-procedure))
(if (procedure? (car exception-procedure))
(set! exception-procedure (car exception-procedure))
(slib:error "Exception Handler Not Procedure:"))
(set! exception-procedure
(lambda (obj . params)
(slib:error "Operation not supported: " obj))))
generic-method)
(define (make-generic-predicate)
(define generic-predicate
(lambda (obj)
(if (object? obj)
(if ((vector-ref obj 1) generic-predicate)
#t
#f)
#f)))
generic-predicate)
(define (make-object . ancestors)
(define method-list
(apply append (map (lambda (obj) (get-all-methods obj)) ancestors)))
(define (make-method! generic-method method)
(set! method-list (cons (cons generic-method method) method-list))
method)
(define (unmake-method! generic-method)
(set! method-list (object:removeq generic-method method-list))
#t)
(define (all-methods) method-list)
(define (get-method generic-method)
(let ((method-def (assq generic-method method-list)))
(if method-def (cdr method-def) #f)))
(vector object:tag get-method make-method! unmake-method! all-methods))
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