;;;;
;;;; object.stk	-- -- A variation of the Gregor Kickzales Tiny CLOS for STklos
;;;; 
;;;; Copyright  1993-2002 Erick Gallesio - I3S-CNRS/ESSI <eg@unice.fr>
;;;; 
;;;; 
;;;; This program is free software; you can redistribute it and/or modify
;;;; it under the terms of the GNU General Public License as published by
;;;; the Free Software Foundation; either version 2 of the License, or
;;;; (at your option) any later version.
;;;; 
;;;; This program is distributed in the hope that it will be useful,
;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;;; GNU General Public License for more details.
;;;; 
;;;; You should have received a copy of the GNU General Public License
;;;; along with this program; if not, write to the Free Software
;;;; Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, 
;;;; USA.
;;;; 
;;;;           Author: Erick Gallesio [eg@unice.fr]
;;;;    Creation date: 20-Feb-1994 21:09
;;;; Last file update: 27-Dec-2002 23:11 (eg)


#|
//FIXMOI

* decoupage du source
* methods rapides
* Vrification que tous les points du mop sont implments

|#



(define class-redefinition (void))	;; forward declaration

;=============================================================================
;
;			      U t i l i t i e s
;
;=============================================================================

(define (%error-bad-class who obj)   (error who "bad class ~S" obj))
(define (%error-bad-generic who obj) (error who "bad generic function ~S" obj))
(define (%error-bad-method who obj)  (error who "bad method ~S" obj))

(define make-closure eval)

(define (specializers l)
  (cond
   ((null? l) '())
   ((pair? l) (cons (if (pair? (car l)) (cadar l) '<top>)
 		    (specializers (cdr l))))
   (else      '<top>)))
 
(define (formals l)
  (if (pair? l)
      (cons (if (pair? (car l)) (caar l) (car l)) (formals (cdr l)))
      l))
 

(define (declare-slots slots)
  ;; This is a *HUGE* *HACK*. Since STklos compiler displays the
  ;; unknown symbols, slots accessors are not known at compilation
  ;; time and yield a message. So, we pre-declare them here.
  ;; In the abolute this code is false, since the keywords :accessor
  ;; :getter and :setter can have a different meaning than the usual
  ;; one for a peculiar meta-class. Anyway, the only risk is to
  ;; trust that a symbol is defined whereas it is not. 
  (for-each (lambda (s)
	      (let ((getter   (slot-definition-getter   s))
		    (setter   (slot-definition-setter   s))
		    (accessor (slot-definition-accessor s)))
		(when getter   (new-global getter))
		(when setter   (new-global setter))
		(when accessor (new-global accessor))))
	    slots)
  slots)


;--------------------------------------------------
(define (make class . l)	;; A temporary version used for bootstrapping 
  (cond
    ((eq? class <generic>) (%make class
				  'generic
				  (key-get l :name '???)))
    ((eq? class <method>) (%make class
				  'method
				  (list (key-get l :generic-function #f)
					(key-get l :specializers     '())
					(key-get l :procedure        '()))))
    (else       	    (error 'basic-make "cannot make ~S with ~S" class l))))

;=============================================================================
;
; 			      Access to Meta objects
;
;=============================================================================

;// ;;;
;// ;;; Methods
;// ;;;
;// (define-method method-body ((m <method>))
;//   (let* ((spec (map class-name (slot-ref m 'specializers)))
;// 	 (proc (procedure-body (slot-ref m 'procedure)))
;// 	 (args (cdadr proc))
;// 	 (body (cddr proc)))
;//     (list* 'method (map list args spec) body)))
;// 

;;;
;;; Classes
;;;
(define (class-name C)
  (if (class? C) (slot-ref C 'name) (%error-bad-class 'class-name C)))

(define (class-direct-supers C)
  (if (class? C) 
      (slot-ref C 'direct-supers) 
      (%error-bad-class 'class-direct-supers C)))

(define (class-direct-slots C)
  (if (class? C) 
      (slot-ref C 'direct-slots) 
      (%error-bad-class 'class-direct-slots C)))

(define (class-direct-subclasses C)
  (if (class? C) 
      (slot-ref C 'direct-subclasses) 
      (%error-bad-class 'class-direct-subclasses C)))

(define (class-direct-methods C)
  (if (class? C) 
      (slot-ref C 'direct-methods) 
      (%error-bad-class 'class-direct-methods C)))

(define (class-precedence-list C)
  (if (class? C)
      (slot-ref C 'cpl)
      (%error-bad-class 'class-precedence-list C)))

(define (class-slots C)
  (if (class? C)
      (slot-ref C 'slots)
      (%error-bad-class 'class-slots C)))

;;;
;;; Slots
;;;
(define (slot-definition-name s)
  (if (pair? s) (car s) s))

(define (slot-definition-options s)
  (and (pair? s) (cdr s)))

(define (slot-definition-allocation s)
  (if (symbol? s)
      :instance
      (key-get (cdr s) :allocation :instance)))

(define (slot-definition-getter s)
  (and (pair? s) (key-get (cdr s) :getter #f)))

(define (slot-definition-setter s)
  (and (pair? s) (key-get (cdr s) :setter #f)))

(define (slot-definition-accessor s)
  (and (pair? s) (key-get (cdr s) :accessor #f)))

(define (slot-definition-init-form s)
  (if (pair? s)
      (key-get (cdr s) :init-form (void))
      (void)))

(define (slot-definition-init-keyword s)
  (and (pair? s) (key-get (cdr s) :init-keyword #f)))

(define (slot-init-function c s)
  (let ((s (slot-definition-name s)))
    (cadr (assq s (slot-ref c 'getters-n-setters)))))

(define (class-slot-definition class slot-name)
  (assq slot-name (class-slots class)))

;;;
;;; Generic functions
;;;
(define (generic-function-name gf)
  (if (generic? gf)
      (slot-ref gf 'name) 
      (%error-bad-generic 'generic-function-name gf)))

(define (generic-function-methods gf)
  (if (generic? gf)
      (slot-ref gf 'methods)
      (%error-bad-generic 'generic-function-methods gf)))

;;;
;;; Methods
;;;
(define (method-generic-function m)
  (if (method? m)
      (slot-ref m 'generic-function)
      (%error-bad-method 'method-generic-function m)))

(define (method-specializers m)
  (if (method? m)
      (slot-ref m 'specializers)
      (%error-bad-method 'method-specializers m)))

(define (method-procedure m)
  (if (method? m)
      (slot-ref m 'procedure)
      (%error-bad-method 'method-procedure m)))

;=============================================================================

;;
;; is-a?
;;
(define (is-a? obj class)
  (and (memq class (class-precedence-list (class-of obj))) #t))

;;
;; Find-class
;;
(define (find-class name :optional (default #f default?))
  (let ((cls (if (symbol? name)
		 (symbol-value* name (current-module) #f)
		 name)))
    (if (is-a? cls <class>)
	cls
	(if default?
	    default
	    (error 'find-class "bad class ~S" name)))))

;;
;; %compute-slots
;;
(define (%compute-slots C)
  (define (remove-duplicate-slots l res)
    (if (null? l) 
	res
	(let ((s (slot-definition-name (car l))))
	  (unless (symbol? s)
	    (error 'compute-slots "bad slot name ~S" s))
	  (remove-duplicate-slots (cdr l) 
				  (if (assq s res) res (cons (car l) res))))))

  (define (build-slots-list cpl res)
    (if (null? cpl) 
	(remove-duplicate-slots (reverse res) '())
	(build-slots-list (cdr cpl) 
			  (append (class-direct-slots (car cpl)) res))))
  (define (sort-slots l)
    ;; Slots are sorted such that instance slots are always before other slots.
    ;; So, virtual slots are placed fist and, for instance, virtual slots can have
    ;; an initial value which depends of real slots.
    ;; Note that the following "sort" just displace non-instance slots at the
    ;; end keeping initial order (i.e. we don't use the STklos sort procedure
    ;; since it is not stable.
    (let Loop ((l l) (instance '()) (other '()))
      (cond
	((null? l)
	   (append (reverse! instance) (reverse! other)))
	((eq? (slot-definition-allocation (car l)) :instance)
	   (Loop (cdr l) (cons (car l) instance) other))
	(else
	   (Loop (cdr l) instance (cons (car l) other))))))
  
  (sort-slots (build-slots-list (class-precedence-list C) '())))


;=============================================================================
;
; 			M e t a c l a s s e s   s t u f f
;
;=============================================================================
(define ensure-metaclass-with-supers
  (let ((table-of-metas '()))
    (lambda (meta-supers)
      (let ((entry (assoc meta-supers table-of-metas)))
	(if entry
	    ;; Found a previously created metaclass
	    (cdr entry)
	    ;; Create a new meta-class which inherit from "meta-supers"
	    (let ((new (make <class> :dsupers meta-supers
			             :slots   '()
				     :name   (gensym "metaclass"))))
	      (set! table-of-metas (cons (cons meta-supers new) table-of-metas))
	      new))))))

(define (ensure-metaclass supers)
  (if (null? supers)
      (find-class <class>)
      (let* ((all-metas (map (lambda (x)
			       (if (is-a? x <class>)
				   x
				   (class-of (find-class x))))
			     supers))
	     (all-cpls  (apply append
			       (map (lambda (m) (cdr (class-precedence-list m))) 
				    all-metas)))
	     (needed-metas '()))
	;; Find the most specific metaclasses.  The new metaclass will be
	;; a subclass of these.
	(for-each
	 (lambda (meta)
	   (when (and (not (member meta all-cpls)) (not (member meta needed-metas)))
	     (set! needed-metas (append needed-metas (list meta)))))
	 all-metas)
	;; Now return a subclass of the metaclasses we found.
	(if (null? (cdr needed-metas))
	    (car needed-metas)  ; If there's only one, just use it.
	    (ensure-metaclass-with-supers needed-metas)))))

;=============================================================================
;
; 			D e f i n e - c l a s s
;
;=============================================================================
;==== Define-class
(define-macro (define-class name supers slots . options)
  `(define ,name 
      (ensure-class
        ',name					; name
	',supers				; supers
	',(declare-slots slots)		; slots 
	,(or (key-get options :metaclass #f)	; metaclass
	     `(ensure-metaclass ',supers))
	,@options)))

;==== Ensure-class
(define (ensure-class name supers slots metaclass . options)

  (define (find-duplicate l)	; find a duplicate in a list; #f otherwise
    (cond
       ((null? l)		#f)
       ((memq (car l) (cdr l))	(car l))
       (else 			(find-duplicate (cdr l)))))
 
  (let ((supers (if (null? supers) 
		    (list <object>)
		    (map find-class supers))))
    ;; Verify that all direct slots are different and that we don't inherit
    ;; several time from the same class
    (let ((tmp (find-duplicate supers)))
      (when tmp
	(error 'define-class "super class ~S is duplicated in class ~S" tmp name)))
    (let ((tmp (find-duplicate (map slot-definition-name slots))))
      (when tmp
	(error 'define-class "slot ~S is duplicated in class ~S" tmp name)))

    ;; Everything seems correct, build the class
    (let ((old (find-class name #f))
	  (cls (apply make metaclass :dsupers supers :slots slots 
		      		     :name name options)))
      (when old (class-redefinition old cls))
      cls)))

;=============================================================================
;
; 			D e f i n e - g e n e r i c
;
;=============================================================================

; ==== Define-generic
(define-macro (define-generic gf)
  `(define ,gf (ensure-generic-function ',gf)))

;==== Ensure-generic-function
(define (ensure-generic-function name)
  (let ((old (symbol-value* name (current-module) #f)))
    (if (generic? old)
	old
	(%symbol-define name 
			(make <generic> :name name 
			      		:default (and (procedure? old) old))
			(current-module)))))

;//(define (ensure-generic-function name)
;//  (let ((old (symbol-value name (current-module) #f)))
;//    (if (generic? old)
;//	old
;//	(eval `(begin
;//		 (define ,name ,(make <generic>
;//				  :name name 
;//				  :default (and (procedure? old) old)))
;//		 ,name)))))
;//

;=============================================================================
;
; 			D e f i n e - m e t h o d
;
;=============================================================================

;==== Add-method!
(define (add-method-in-classes! m)
  ;; Add method in all the classes which appears in its specializers list
  (for-each* (lambda (x)
	       (let ((dm (class-direct-methods x)))
		 (unless (memq m dm)
		   (slot-set! x 'direct-methods (cons m dm)))))
	     (method-specializers m)))

(define (remove-method-in-classes! m)
  ;; Remove method in all the classes which appears in its specializers list
  (for-each* (lambda (x)
	       (slot-set! x 'direct-methods (delete! m (class-direct-methods x)
						     eq?)))
	      (method-specializers m)))

(define (compute-new-list-of-methods gf new)
  (let ((new-spec (method-specializers new))
	(methods  (generic-function-methods gf)))
    (let Loop ((l methods))
      (if (null? l)
	  (cons new methods)
	  (if (equal? (method-specializers (car l)) new-spec)
	      (begin 
		;; This spec. list already exists. Remove old method from dependents
		(remove-method-in-classes! (car l))
		(set-car! l new) 
		methods)
	      (Loop (cdr l)))))))

;;
;; Add-method!
;;
(define (add-method! gf m)
  (slot-set! gf 'methods (compute-new-list-of-methods gf m))
  (add-method-in-classes! m)
  m)


(define (ensure-method gf args body :optional kind-of-method)
  (let* ((new  (extended-lambda->lambda `(method ,args ,@body)))
	 (args (cadr new))
	 (body (cddr new)))
    (make (or kind-of-method <method>)
          :generic-function gf
	  :specializers     (map* find-class (specializers args))
	  :procedure        (make-closure `(let ((next-method (void)))
					     (lambda ,(formals args)
					       ,@body))))))


;====  Method
(define-macro (method args . body)
  `(ensure-method #f ',args ',body))


; ==== Define-method
(define-macro (define-method name args . body)
  (let ((gf (gensym "gf")))
    `(let ((,gf (ensure-generic-function ',name)))
       (add-method! ,gf (ensure-method ,gf ',args ',body))
       (values (void) ',name))))

;=============================================================================
;
; 			    Standard methods   
; 			used by the C runtime
;
;=============================================================================

;==== Methods to compare objects
(define-method object-eqv?   (x y) #f)
(define-method object-equal? (x y) (eqv? x y))

 
;==== Methods to display/write an object
 
;     Code for writing objects must test that the slots they use are
;     bound. Otherwise a slot-unbound method will be called and will 
;     conduct to an infinite loop.
 
;; Write
(define-method write-object (o file)
  (format file "#[instance ~A]" (number->string (address-of o) 16)))
 
(define-method write-object ((o <object>) file)
  (let ((class (class-of o)))
    (if (slot-bound? class 'name) 
	(format file "#[~A ~A]" (class-name class) 
		(number->string (address-of o) 16))
	(next-method))))

(define-method write-object((class <class>) file)
  (let ((meta (class-of class)))
    (if (and (slot-bound? class 'name) (slot-bound? meta 'name)) 
	(format file "#[~A ~A ~A]" (class-name meta) (class-name class)
		(number->string (address-of class) 16))
	(next-method))))

(define-method write-object((gf <generic>) file)
  (let ((meta (class-of gf)))
    (if (and (slot-bound? gf 'name) (slot-bound? meta 'name)
	     (slot-bound? gf 'methods))
	(format file "#[~A ~A (~A)]" 
		(class-name meta)
		(generic-function-name gf)
		(length (generic-function-methods gf)))
	(next-method))))

;; Display (do the same thing as write by default)
(define-method display-object (o file) 
  (write-object o file))

;==== Slot access

;; Avoid printing object itself in the error message, because it might
;; cause an infinite loop (via write-object method). Problem signaled
;; by Shiro Kawai <shiro@acm.org>.

(define-method slot-unbound ((c <class>) (o <object>) s)
  (error "slot ~S is unbound in #p~A (an object of class ~S)"
	 s (number->string (address-of o) 16) c))

(define-method slot-missing ((c <class>) (o <object>) name :optional value)
  (error "no slot with name `~S' in #p~A (an object of class ~S)"
	 name (number->string (address-of o) 16) c))

; ==== Methods for the possible error we can encounter when calling a gf

(define-method no-next-method ((gf <generic>) method args)
  (error "no next method for ~S in call ~S" 
	 method (cons (generic-function-name gf) args)))

(define-method no-applicable-method ((gf <generic>) args)
  (error "no applicable method for ~S\nin call ~S"
	 gf (cons (generic-function-name gf) args)))

(define-method no-method ((gf <generic>) args)
  (error "no method defined for ~S"  gf))


;// (define-macro (next-method-exists?)
;//  `((with-module STklos %next-method-exists?) next-method))



;=============================================================================
;
;	      Cloning functions (from Rob Deline <rdeline@CS.CMU.EDU>)
;
;=============================================================================
(define-method shallow-clone ((self <object>))
  (let ((clone (%allocate-instance (class-of self)))
	(slots (map slot-definition-name
		    (class-slots (class-of self)))))
    (for-each (lambda (slot)
		(if (slot-bound? self slot)
		    (slot-set! clone slot (slot-ref self slot))))
	      slots)
    clone))

(define-method deep-clone ((self <object>))
  (let ((clone (%allocate-instance (class-of self)))
	(slots (map slot-definition-name
		    (class-slots (class-of self)))))
    (for-each (lambda (slot)
		(if (slot-bound? self slot)
		    (slot-set! clone slot
			       (let ((value (slot-ref self slot)))
				 (if (instance? value)
				     (deep-clone value)
				     value)))))
	      slots)
    clone))

;=============================================================================
;
; 		     	Class redefinition utilities
;;
;=============================================================================

;==== Remove-class-accessors
(define-method remove-class-accessors ((c <class>))
  (for-each 
     (lambda (m) (if (is-a? m <accessor-method>) (remove-method-in-classes! m)))
     (class-direct-methods c)))


;==== Update-direct-method
(define-method update-direct-method ((m  <method>) (old <class>) (new <class>))
  (let Loop ((l (method-specializers m)))
    (when (pair? l)       	; Note: the <top> in dotted list is never used. 
      (if (eq? (car l) old)     ; So we can work if we had only proper lists.
	(set-car! l new))
      (Loop (cdr l)))))

;==== Update-direct-subclass
(define-method update-direct-subclass ((c <class>) (old <Class>) (new <Class>))
  (let ((new-supers (map (lambda (cls) (if (eq? cls old) new cls))
			 (class-direct-supers c))))
    ;; Create a new class with same name as c. This will automagically call 
    ;; class-redefinition on this subclass and redefine all its descent
    (ensure-class (class-name c)
		  new-supers
		  (class-direct-slots c)
		  (class-of c))))

;==== Class-redefinition
(define-method class-redefinition ((old <class>) (new <class>))
  ;; Work on direct methods:
  ;;		1. Remove accessor methods from the old class 
  ;;		2. Patch the occurences of old in the specializers by new
  ;;		3. Displace the methods from old to new
  (remove-class-accessors old)					;; -1-
  (let ((methods (class-direct-methods old)))
    (for-each (lambda (m) (update-direct-method m old new))	;; -2-
	      methods)
    (slot-set! new 'direct-methods methods))			;; -3-

  ;; Remove the old class from the direct-subclasses list of its super classes
  (for-each (lambda (c) (slot-set! c 'direct-subclasses 
				   (delete! old (class-direct-subclasses c) eq?)))
	    (class-direct-supers old))

  ;; Redefine all the subclasses of old to take into account modification
  (for-each 
       (lambda (c) (update-direct-subclass c old new))
       (class-direct-subclasses old))

  ;; Invalidate class so that subsequent instances slot accesses invoke
  ;; change-object-class
  (slot-set! old 'redefined new))


;=============================================================================
;
; 			Utilities for INITIALIZE methods
;
;=============================================================================


;;;
;;; Compute-get-n-set
;;;
(define-method compute-get-n-set ((class <class>) s)
  (case (slot-definition-allocation s)
    ((:instance) ;; Instance slot
     		 ;; get-n-set is just its offset
     		 (let ((already-allocated (slot-ref class 'nfields)))
		   (slot-set! class 'nfields (+ already-allocated 1))
		   already-allocated))

    ((:class)  ;; Class slot
               ;; Class-slots accessors are implemented as 2 closures around 
     	       ;; a Scheme variable. 
               (let ((name (slot-definition-name s)))
		 (if (memq name (map slot-definition-name 
				     (class-direct-slots class)))
		     ;; This slot is direct; create a new shared cell
		     (let ((shared-cell (void)))
		       (list (lambda (o)   shared-cell)
			     (lambda (o v) (set! shared-cell v))))
		     ;; Slot is inherited. Find its definition in superclass
		     (let Loop ((l (cdr (class-precedence-list class))))
		       (let ((r (assq name (slot-ref (car l) 'getters-n-setters))))
			 (if r
			     (cddr r)
			     (Loop (cdr l))))))))

    ((:each-subclass) ;; slot shared by instances of direct subclass.
     		      ;; (Thomas Buerger, April 1998)
     		      (let ((shared-cell (void)))
			(list (lambda (o)   shared-cell)
			      (lambda (o v) (set! shared-cell v)))))

    ((:virtual) ;; No allocation
     		;; slot-ref and slot-set! function must be given by the user
     	     	(let ((get (key-get (slot-definition-options s) :slot-ref  #f))
		      (set (key-get (slot-definition-options s) :slot-set! #f)))
		  (unless (and get set)
		    (error "a :slot-ref and a :slot-set! must be supplied in ~S" s))
		  (list (make-closure get)
			(make-closure set))))
    ((:active) ;; Active slot
     	       ;; active slots admit a daemon before or after slot access
               (let* ((index 	   (slot-ref class 'nfields))
		      (name	   (car s))
		      (s	   (cdr s))
		      (before-ref  (make-closure (key-get s :before-slot-ref  #f)))
		      (after-ref   (make-closure (key-get s :after-slot-ref   #f)))
		      (before-set! (make-closure (key-get s :before-slot-set! #f)))
		      (after-set!  (make-closure (key-get s :after-slot-set!  #f))))
		 (slot-set! class 'nfields (+ index 1))
		 (list (lambda (o)
			 (if before-ref
			     (if (before-ref o)
				 (let ((res (%fast-slot-ref o index)))
				   (and after-ref
					(not (eqv? res (void)))
					(after-ref o))
				   res)
				 (void))
			     (let ((res (%fast-slot-ref o index)))
			       (and after-ref (not (eqv? res (void))) (after-ref o))
			       res)))
		       (lambda (o v) 
			 (if before-set!
			     (when (before-set! o v)
			       (%fast-slot-set! o index v)
			       (and after-set! (after-set! o v)))
			     (begin
			       (%fast-slot-set! o index v)
			       (and after-set! (after-set! o v))))))))
    (else    (next-method))))

(define-method compute-get-n-set ((o <object>) s)
  (error "allocation type \"~S\" is unknown" (slot-definition-allocation s)))


;;;
;;; compute-slot-accessors
;;;
(define (compute-slot-accessors class slots)
  (for-each
      (lambda (s)
	(let ((name     (slot-definition-name     s))
	      (getter   (slot-definition-getter   s))
	      (setter   (slot-definition-setter   s))
	      (accessor (slot-definition-accessor s)))
	  (when getter
	    (let ((gf (ensure-generic-function getter)))
	      (add-method! gf (ensure-method gf '(o) `((slot-ref o ',name))
					     <accessor-method>))))
	  (when setter
	    (let ((gf (ensure-generic-function setter)))
	      (add-method! gf (ensure-method gf '(o v) `((slot-set! o ',name v))
					     <accessor-method>))))
	  (when accessor
	    (let ((gf (ensure-generic-function accessor)))
	      (add-method! gf (ensure-method gf '(o) `((slot-ref o ',name))
					     <accessor-method>))
	      (add-method! gf (ensure-method gf '(o v) `((slot-set! o ',name v))
					     <accessor-method>))))))
      slots))

;;;
;;; compute-getters-n-setters
;;; 

(define (compute-getters-n-setters class slots)

  (define (compute-slot-init-function s)
    (let ((init (slot-definition-init-form s)))
      (cond
	((eq? init (void))
	   #f)
	((eq? (slot-definition-allocation s) :class)
	   (let ((sn (slot-definition-name s)))
	     (make-closure `(lambda (o)
			      (let ((val (%slot-ref o ',sn)))
				(if (eq? val (void))
				    ,init
				    val))))))
	(else
	   (make-closure `(lambda (o) ,init))))))


  (define (verify-accessors slot l)
    (if (pair? l)
	(let ((get (car l)) 
	      (set (cadr l)))
	  (unless (and (closure? get) (= (%procedure-arity get) 1))
	    (error "bad getter closure for slot `~S' in ~S: ~S" slot class get))
	  (unless (and (closure? set) (= (%procedure-arity set) 2))
	    (error "bad setter closure for slot `~S' in ~S: ~S" slot class set)))))

  (map (lambda (s)
	 (let* ((s     (if (pair? s) s (list s)))
		(g-n-s (compute-get-n-set class s))
		(name  (slot-definition-name s)))
	   ;; For each slot we have '(name init-function getter setter)
	   ;; If slot is an instance one, we have the simplest
	   ;; form '(name init-function . index)
	   (verify-accessors name g-n-s)
	   (list* name (compute-slot-init-function s) g-n-s)))
       slots))

;;;
;;; compute-cpl
;;;
;;; The current implementation was provided by Anthony Beuriv
;;; <beurive@labri.u-bordeaux.fr>. This implementation is monotonic and 
;;; works "by level". For more information on monotonic superclass 
;;; linearization  algorithm look at the paper 
;;; 	A Monotonic Superclass Linearization for Dylan, 
;;;     K. Barrett, B. Cassels, P. Haahr, D. A. Moon, K. Playford, 
;;;     P. Tucker Withington, 
;;;     OOPSLA 96.
;;; also available at 
;;;	http://www.webcom.com/~haahr/dylan/linearization-oopsla96.html
;;;
(define (compute-cpl class)

  (define (reduce sequences cpl)
    (define (aux sequence)
      (if (and (pair? sequence) (memq (car sequence) cpl))
	  (aux (cdr sequence))
	  sequence))
    (map aux sequences))

  (define (delete-null-lists sequences)
    (if (pair? sequences)
	(let ((first (car sequences)))
	  (if (pair? first)
	      (cons first (delete-null-lists (cdr sequences)))
	      (delete-null-lists (cdr sequences))))
	'()))

  (define (select-candidate candidate sequences)
    (if (pair? sequences)
	(and (not (memq candidate (cdr (car sequences))))
	     (select-candidate candidate (cdr sequences)))
	candidate))

  (define (filter-candidates candidates sequences)
    (if (pair? candidates)
	(or (select-candidate (car candidates) sequences)
	    (filter-candidates (cdr candidates) sequences))
	#f)) ; No valid candidate (inconsistency).

  (define (next-class sequences)
    (let ((candidates (map car sequences)))
      (or (filter-candidates candidates sequences)
	  (car candidates)))) ; Arbitrarily brake the inconsistency.

  (define (step cpl sequences)
    (if (pair? sequences)
	(let ((new-cpl (cons (next-class sequences) cpl)))
	  (step new-cpl (delete-null-lists (reduce sequences new-cpl))))
	(reverse cpl)))

  (step '() (let ((supers (slot-ref class 'direct-supers)))
	      (cons (cons class supers)
		    (map (lambda (super)
			   (slot-ref super 'cpl))
			 supers)))))


;=============================================================================
;
; 			    I n i t i a l i z e
;
;=============================================================================

(define-method initialize ((object <object>) initargs)
  (%initialize-object object initargs))

(define-method initialize ((class <class>) initargs)
  (next-method)
  (let ((dslots (key-get initargs :slots   '()))
	(supers (key-get initargs :dsupers '())))

    (slot-set! class 'name	  	(key-get initargs :name '???))
    (slot-set! class 'direct-supers 	supers)
    (slot-set! class 'direct-slots  	dslots)
    (slot-set! class 'direct-subclasses '())
    (slot-set! class 'direct-methods    '())
    (slot-set! class 'cpl		(compute-cpl class))
    (slot-set! class 'redefined		#f)
    (let ((slots (%compute-slots class)))
      (slot-set! class 'slots	  	  slots)
      (slot-set! class 'nfields	  	  0)
      (slot-set! class 'getters-n-setters (compute-getters-n-setters class slots)))
    ;; Update the "direct-subclasses" of each inherited classes
    (for-each (lambda (x)
		(slot-set! x 'direct-subclasses
			   (cons class (slot-ref x 'direct-subclasses))))
	      supers)

    ;; Build getters - setters - accessors
    (compute-slot-accessors class dslots)))


(define-method initialize ((generic <generic>) initargs)
  (let ((previous-definition (key-get initargs :default #f)))
    (next-method)
    (slot-set! generic 'name    (key-get initargs :name '???))
    (slot-set! generic 'methods (if (procedure? previous-definition)
				    (list (make <method>	; /// FAST-METHOD
						:specializers <top>
						:procedure
						    (lambda (nm . l)
						      (apply previous-definition 
							     l))))
				    '()))))

(define-method initialize ((method <method>) initargs)
  (next-method)
  (slot-set! method 'generic-function (key-get initargs :generic-function #f))
  (slot-set! method 'specializers     (key-get initargs :specializers '()))
  (slot-set! method 'procedure        (key-get initargs :procedure (lambda l '()))))


;=============================================================================
;
; 				     M a k e 
;
;     A new definition which overwrite the previous one which was built-in
;
;=============================================================================

(define-method allocate-instance ((class <class>) initargs)
  (%allocate-instance class))

(define-method make-instance ((class <class>) . initargs)   ;// VIRER CE SYMBOLE
  (let ((instance (allocate-instance class initargs)))
    (initialize instance initargs)
    instance))

(define make make-instance)

;=============================================================================
;
; 			C h a n g e - c l a s s
;
;=============================================================================

(define (change-object-class old-instance old-class new-class)
  (let ((new-instance (allocate-instance new-class ())))
    ;; Initalize the slot of the new instance
    (for-each (lambda (slot)
		(if (slot-exists-using-class? old-class old-instance slot)
		    ;; Slot was present in old instance; set it 
		    (if (slot-bound-using-class? old-class old-instance slot)
			(slot-set-using-class!
			     new-class 
			     new-instance 
			     slot 
			     (slot-ref-using-class old-class old-instance slot)))
		    ;; slot was absent; initialize it with its default value
		    (let ((init (slot-init-function new-class slot)))
		      (if init
			  (slot-set-using-class!
			       new-class 
			       new-instance 
			       slot
			       (apply init '()))))))
	      (map slot-definition-name (class-slots new-class)))
    ;; Exchange old an new instance in place to keep pointers valids
    (%modify-instance old-instance new-instance)
    old-instance))


(define-method change-class ((old-instance <object>) (new-class <class>))
  (change-object-class old-instance (class-of old-instance) new-class))

;=============================================================================
;
;				a p p l y - g e n e r i c
;
; Protocol for calling standard generic functions.
; This protocol is  not used for real <generic> functions (in this case we use
; a completely C hard-coded protocol). 
; Apply-generic is used by STklos for calls to subclasses of <generic>.
;
; The code below is similar to the first MOP described in AMOP. In particular,
; it doesn't used the currified approach to gf call. There are 3 reasons for 
; that: 
;   - the protocol below is exposed to mimic completely the one written in C
;   - the currified protocol would be imho inefficient in C.
;   - nobody (except persons really interested with playing with a MOP) will 
;     probably use the following code
;=============================================================================
 
(define-method compute-applicable-methods ((gf <generic>) args)
  (apply find-method gf args))

(define-method method-more-specific? ((m1 <method>) (m2 <method>) targs)
  (%method-more-specific? m1 m2 targs))

(define-method sort-applicable-methods ((gf <generic>) methods args)
  (let ((targs (map class-of args)))
    (sort methods (lambda (m1 m2) (method-more-specific? m1 m2 targs)))))
 
(define-method apply-method ((gf <generic>) methods build-next args)
  (let ((proc (method-procedure (car methods))))
    (%set-next-method! proc (build-next methods args))
    (apply proc args)))

(define-method apply-methods ((gf <generic>) (l <list>) args)
  (letrec ((next (lambda (procs args)
		   (lambda new-args
		     (let ((a (if (null? new-args) args new-args)))
		       (if (null? (cdr procs))
			   (no-next-method gf (car procs) a)
			   (apply-method gf (cdr procs) next a)))))))
    (apply-method gf l next args)))


;; ==== apply-generic

(define-method apply-generic ((gf <generic>) args)
  (if (null? (generic-function-methods gf))
      (no-method gf args))
  (let ((methods (compute-applicable-methods gf args)))
    (if methods
	(apply-methods gf (sort-applicable-methods gf methods args) args)
 	(no-applicable-method gf args))))


;// ;=============================================================================
;// ;
;// ;		     <Composite-metaclass> 
;// ;=============================================================================


;// 
;// (export <Composite-metaclass> <Active-metaclass>)
;// 

;=============================================================================
;
; 				T o o l s
;
;=============================================================================
(define class-subclasses #f)
(define class-methods    #f)

(let ()
  (define (list2set l)
    (let Loop ((l l) (res '()))
      (cond
       ((null? l) 	   res)
       ((memq (car l) res) (Loop (cdr l) res))
       (else		   (Loop (cdr l) (cons (car l) res))))))

  (define (mapappend func . args)
    (if (memq '()  args)
	'()
	(append (apply func (map car args))
		(apply mapappend func (map cdr args)))))
 
  ;; ==== class-subclasses  
  (set! class-subclasses 
	(lambda (c)
	  (letrec ((allsubs (lambda (c)
			      (cons c (mapappend allsubs 
						 (class-direct-subclasses c))))))
	    (list2set (cdr (allsubs c))))))
  ;; ==== class-methods
  (set! class-methods 
	(lambda (c)
	  (list2set (mapappend class-direct-methods 
			       (cons c (class-subclasses c)))))))

;==== CLOS like slot-value (but as a gf instead of proc as slot-ref or slot-set!) 
(define-method slot-value ((o <object>) s) 		;; The getter
  (slot-ref o s))
 
(define-method slot-value ((o <object>) s v)		;; The setter
  (slot-set! o s v))


(autoload "describe" describe)



;// FIXME:
(%object-system-initialized)


; LocalWords:  supers metaclass OOPSLA linearization beurive labri fr Cassels
; LocalWords:  Beuriv Playford Withington Haahr Gregor Kickzales init