-#?(or (not (sbcl>= 0 9 14)) (featurep :clisp))
-(defmethod slot-value-using-class
- ((class virtual-slots-class) (object virtual-slots-object)
- (slotd effective-virtual-slot-definition))
- (funcall (slot-value slotd 'reader-function) object))
-
-#?(or (not (sbcl>= 0 9 14)) (featurep :clisp))
-(defmethod slot-boundp-using-class
- ((class virtual-slots-class) (object virtual-slots-object)
- (slotd effective-virtual-slot-definition))
- (funcall (slot-value slotd 'boundp-function) object))
-
-#?(or (not (sbcl>= 0 9 14)) (featurep :clisp))
-(defmethod (setf slot-value-using-class)
- (value (class virtual-slots-class) (object virtual-slots-object)
- (slotd effective-virtual-slot-definition))
- (funcall (slot-value slotd 'writer-function) value object))
-
-(defmethod slot-makunbound-using-class
- ((class virtual-slots-class) (object virtual-slots-object)
- (slotd effective-virtual-slot-definition))
- (funcall (slot-value slotd 'makunbound-function) object))
-
+(defmacro vsc-slot-x-using-class (x x-slot-name computer
+ &key allow-string-fun-p setf-p)
+ (let ((generic-name (intern (concatenate 'string
+ "SLOT-" (string x) "-USING-CLASS"))))
+ `(defmethod ,(if setf-p `(setf ,generic-name) generic-name)
+ (,@(when setf-p '(value))
+ (class virtual-slots-class) (object virtual-slots-object)
+ (slotd effective-virtual-slot-definition))
+ (unless (and (slot-boundp slotd ',x-slot-name)
+ ,@(when allow-string-fun-p
+ `((not (stringp (slot-value slotd ',x-slot-name))))))
+ (setf (slot-value slotd ',x-slot-name) (,computer slotd)))
+ (funcall (slot-value slotd ',x-slot-name)
+ ,@(when setf-p '(value))
+ object))))
+
+(vsc-slot-x-using-class value getter compute-slot-reader-function
+ :allow-string-fun-p t)
+(vsc-slot-x-using-class value setter compute-slot-writer-function
+ :allow-string-fun-p t :setf-p t)
+
+(vsc-slot-x-using-class boundp boundp-function compute-slot-boundp-function)
+(vsc-slot-x-using-class makunbound makunbound-function
+ compute-slot-makunbound-function)