;;; Paul Y Gloess, http://www.enseirb-matmeca.fr/~gloess

;;; created 15 February 2011, last edition 25 March 2011


;;; Purpose: DEFCL is a simplified version of DEFCLASS

;;;           for pure LISP: no side-effects, standard

;;;           :reader and :initarg.

;;;          NEW is a short for MAKE-INSTANCE.


(in-package :common-lisp-user)

(defmacro defcl (class-name



                 &body slot-specs)

  "Assuming CLASS-NAME is a symbol, and SUPER-CLASS-LIST is a list

    of just one symbol, CLASS-DOCUMENTATION-STRING is a string,

    and SLOT-SPECS is defined by the grammar

         slot-specs ::=   ()

                        | (slot-spec . slot-specs)

          slot-spec ::=   slot-name       ; means the same as (slot-name nil).

                        | (slot-name)     ; means no default.

                        | (slot-name slot-default)

          slot-name ::= symbol            ; all slot-name should be distinct.

       slot-default ::= lisp-form         ; valid in the context of defcl.        


expands into a DEFCLASS that derives standard :READER and :INITARG

 and :INITFORM (when there is a slot-default) from each slot-spec in SLOT-SPECS,

 see code for detail!"

  (when (and (consp super-class-list) (consp (cdr super-class-list)))

    (warn "~%Multiple inheritance ~a is not a good idea!~%

Please try to stick to one superclass only!"


  `(defclass ,class-name ,super-class-list

     ,(mapcar (lambda (slot-spec)

                (let ((slot-name (if (consp slot-spec)

                                      (car slot-spec)


                  (unless (symbolp slot-name)

                    (error "~%Invalid slot name ~a in slot spec ~a." slot-name slot-spec))

                  `(,slot-name :initarg ,(intern (symbol-name slot-name) :keyword)

                               :reader ,slot-name

                               . ,(cond ((and (consp slot-spec) (consp (cdr slot-spec)))

                                         `(:initform ,(second slot-spec)))

                                        ((atom slot-spec)

                                         `(:initform nil))

                                        (t nil)))))   ; (slot-name) => no default.


     (:documentation ,class-documentation-string)))

;;; (load "defcl")

;;; (macroexpand-1 '(defcl person () "A person" name (sex 'female) (age)))

;;; (macroexpand-1 '(defcl employee (person) "An employee" salary))

(defmacro new (&rest args)

  "Just a short synonymous of MAKE-INSTANCE CLOS function."

  `(make-instance . ,args))

;;; Evaluate the following forms in THIS ORDER in *slime-repl sbcl* buffer

;;;  (DO NOT use C-x C-e !):


;;; (load "defcl")

;;; (defcl person () "A person" name (sex 'female) (age))

;;; (defcl employee (person) "An employee" salary)

;;; (new 'person :sex 'male :age 50 :name "Michael Jackson")

;;;   (name *)

;;; (name (new 'person))   ; => NIL

;;; (sex (new 'person))    ; => FEMALE

;;; (age (new 'person))    ; ERROR because AGE is unbound!

;;; (new 'employee :sex 'female :age 45 :name "Madonna" :salary 50000000000000)

;;;   (name *)

;;;   (salary **)

(provide "DEFCL")