;;; Packages.
(defpackage #:mdw.mop
- (:use #:common-lisp #+cmu #:pcl)
+ (:use #:common-lisp #:mdw.base #+(or cmu clisp) #:mop)
(:export #:compatible-class
+ #:copy-instance #:copy-instance-using-class
#:initargs-for-effective-slot #:make-effective-slot
#:filtered-slot-class-mixin
#:filtered-direct-slot-definition
#:filtered-effective-slot-definition
#:predicate-class-mixin
#:abstract-class-mixin #:instantiate-abstract-class
- #:mdw-class #:abstract-class
+ #:singleton-class-mixin
+ #:mdw-class #:abstract-class #:singleton-class
#:print-object-with-slots))
(in-package #:mdw.mop)
(eq (class-of sub) (find-class 'standard-class)))
;;;--------------------------------------------------------------------------
+;;; Copying instances.
+
+(defgeneric copy-instance-using-class (class object &rest initargs)
+ (:documentation
+ "Does the donkey-work behind copy-instance."))
+
+(defmethod copy-instance-using-class
+ ((class standard-class) object &rest initargs)
+ (let ((new (apply #'allocate-instance class initargs)))
+ (dolist (slot (class-slots class))
+ (setf (slot-value-using-class class new slot)
+ (slot-value-using-class class object slot)))
+ (apply #'shared-initialize new nil initargs)
+ new))
+
+(defun copy-instance (object &rest initargs)
+ "Make a copy of OBJECT, modifying it by setting slots as requested by
+ INITARGS."
+ (apply #'copy-instance-using-class (class-of object) object initargs))
+
+;;;--------------------------------------------------------------------------
;;; Utilities for messing with slot options.
(defgeneric initargs-for-effective-slot (class direct-slots)
(defmethod compute-effective-slot-definition
((class compatible-class) slot-name direct-slots)
"Construct an effective slot definition for the given slot."
+ (declare (ignore slot-name))
;;
;; Ideally we don't want to mess with a slot if it's entirely handled by
;; the implementation. This check seems to work OK.
(error 'instantiate-abstract-class :class class))
;;;--------------------------------------------------------------------------
+;;; Singleton classes.
+
+(defclass singleton-class-mixin (compatible-class)
+ ((instance :initform nil :type (or null standard-object)))
+ (:documentation
+ "A class which has only one instance. All calls to `make-instance' return
+ the same object."))
+
+(defmethod allocate-instance ((class singleton-class-mixin) &key)
+ "If the class already has an instance, return it; otherwise allocate one,
+ store it away, and return that."
+ (with-slots (instance) class
+ (or instance
+ (setf instance (call-next-method)))))
+
+;;;--------------------------------------------------------------------------
;;; Useful classes.
(defclass mdw-class (filtered-slot-class-mixin
features."))
(defclass abstract-class (mdw-class abstract-class-mixin) ())
+(defclass singleton-class (mdw-class singleton-class-mixin) ())
;;;--------------------------------------------------------------------------
;;; Printing things.
(defun print-object-with-slots (obj stream)
"Prints objects in a pleasant way. Not too clever about circularity."
- (let ((class (pcl:class-of obj))
+ (let ((class (class-of obj))
(magic (cons 'magic nil)))
(print-unreadable-object (obj stream)
(pprint-logical-block
(if (slot-boundp-using-class class obj slot)
(slot-value-using-class class obj slot)
magic)))
- (pcl:class-slots class)))
- (format stream "~S" (pcl:class-name class))
+ (class-slots class)))
+ (format stream "~S" (class-name class))
(let ((sep nil))
(loop
(pprint-exit-if-list-exhausted)
(progn (format stream " ~@_~:I") (setf sep t)))
(let ((name (pprint-pop))
(value (pprint-pop)))
- (format stream "~S ~@_~:[~S~;<unbound>~*~]"
+ (format stream "~S ~@_~:[~W~;#<unbound>~*~]"
name (eq value magic) value))))))))
;;;----- That's all, folks --------------------------------------------------