gistfile1.lisp

(defclass myclass (c2mop:funcallable-standard-object)
  ()
  (:metaclass c2mop:funcallable-standard-class))


(defmethod call ((obj myclass) mesg &rest args)
  (error "foo?"))

(defmethod initialize-instance :before ((self myclass)
                                        &key definition-source lambda-list
                                        name)
  (c2mop:set-funcallable-instance-function self
                                           (lambda (mesg &rest args)
                                             (apply #'call self mesg args))))


(defclass foo (myclass)
  ((x :initform 0 :initarg :x)
   (y :initform 1 :initarg :y)
   (z :initform 2 :initarg :z))
  (:metaclass c2mop:funcallable-standard-class))


;;; 
;;; 
;;; 

(defmethod call ((self foo) (mesg (eql :x)) &rest args)
  (slot-value self 'x))


(defmethod call ((self foo) (mesg (eql :set-x)) &rest args)
  (setf (slot-value self 'x) (car args)))


(defun send (obj &rest mesgs)
  (apply obj mesgs))


(let ((o (make-instance 'foo :x 42)))
  (print (send o :x))
  (send o :set-x (* 2 (send o :x)))
  (print (send o :x)))
;>>  
;>>  42 
;>>  84 
;=>  84


(defclass bar (foo)
  ((a :initform 100))
  (:metaclass c2mop:funcallable-standard-class))


(defmethod call ((self foo) (mesg (eql :a)) &rest args)
  (slot-value self 'a))


(let ((o (make-instance 'bar :x 42)))
  (print (list (send o :x) (send o :a)))
  (send o :set-x (* 2 (send o :x)))
  (print (send o :x)))
;>>  
;>>  (42 100) 
;>>  84 
;=>  84