;;; Packages.
(defpackage #:mdw.mop
- (:use #:common-lisp #:mdw.base #+cmu #:pcl)
- (:export #:compatible-class
+ (:use #:common-lisp #:mdw.base #+(or cmu clisp) #:mop)
+ (:export #:copy-instance #:copy-instance-using-class
+ #:with-slot-variables
+ #:compatible-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)
+;;;--------------------------------------------------------------------------
+;;; 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))
+
+;;;--------------------------------------------------------------------------
+;;; Handy macros.
+
+(defmacro with-slot-variables (slots instance &body body)
+ "A copy-out-and-write-back variant of with-slots.
+
+ The SLOTS argument is a list of slot specifications, each of which has the
+ form (NAME &key :update :variable). VARIABLE defaults to NAME, and
+ :update defaults to nil.
+
+ The INSTANCE argument has the form (INSTANCE &key :class), but an atom may
+ be used in place of a singleton list. If the CLASS is specified, then two
+ good things happen: firstly the INSTANCE is declared to be a member of the
+ CLASS, and secondly all the slot variables are declared to have the
+ appropriate types, as dredged up from the class's effective slot
+ definitions.
+
+ The effect of all this is to return the result of evaluating BODY in an
+ environment where the VARIABLEs are bound to the values of the NAMEd slots
+ of the given INSTANCE. If BODY completes successfully (rather than
+ throwing out, restarting, or anything like that) then the final values of
+ VARIABLEs for which UPDATE was set non-nil are written back to their
+ corresponding slots.
+
+ This stands a good chance of being rather faster than with-slots. It
+ does, however, run the risk of leaving things in an inconsistent state if
+ BODY escapes half-way through. Also, this requires recompilation if a
+ class's slots change type."
+ (multiple-value-bind (instance class)
+ (destructuring-bind
+ (instance &key class)
+ (listify instance)
+ (values instance (and class (find-class class))))
+ (let ((slots (mapcar (lambda (slot)
+ (destructuring-bind
+ (name &key update (variable name))
+ (listify slot)
+ (list name variable update)))
+ (if slots
+ (listify slots)
+ (mapcar #'slot-definition-name
+ (class-slots class))))))
+ (multiple-value-bind
+ (docs decls body)
+ (parse-body body :allow-docstring-p nil)
+ (declare (ignore docs))
+ (with-gensyms (instvar)
+ `(let ((,instvar ,instance))
+ ,@(and class `((declare (type ,(class-name class) ,instvar))))
+ (let ,(loop for (name var update) in slots
+ collect `(,var (slot-value ,instvar ',name)))
+ ,@(and class
+ `((declare
+ ,@(loop
+ for (name var update) in slots
+ for slot = (or (find name
+ (class-slots class)
+ :key #'slot-definition-name)
+ (error
+ "Slot ~S not found in class ~S."
+ name (class-name class)))
+ collect `(type
+ ,(slot-definition-type slot)
+ ,name)))))
+ ,@decls
+ (multiple-value-prog1
+ (progn ,@body)
+ ,@(loop for (name var update) in slots
+ when update
+ collect `(setf (slot-value ,instvar ',name)
+ ,var))))))))))
+
;;;--------------------------------------------------------------------------
;;; Basic stuff.
(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.
(declare (ignore whatever))
(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.
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)
~mdw / lisp / blobdiff