Language/OS - Multiplatform Resource Library/LANGUAGE OS.iso/pcl/sptmbr16.lha/macros.lisp

Lisp/Scheme | 1993-01-07 | 25KB | 744 lines

;;;-*-Mode:LISP; Package:(PCL (LISP WALKER)); Base:10; Syntax:Common-lisp -*-
;;;
;;; *************************************************************************
;;; Copyright (c) 1985, 1986, 1987, 1988, 1989, 1990 Xerox Corporation.
;;; All rights reserved.
;;;
;;; Use and copying of this software and preparation of derivative works
;;; based upon this software are permitted.  Any distribution of this
;;; software or derivative works must comply with all applicable United
;;; States export control laws.
;;;
;;; This software is made available AS IS, and Xerox Corporation makes no
;;; warranty about the software, its performance or its conformity to any
;;; specification.
;;;
;;; Any person obtaining a copy of this software is requested to send their
;;; name and post office or electronic mail address to:
;;;   CommonLoops Coordinator
;;;   Xerox PARC
;;;   3333 Coyote Hill Rd.
;;;   Palo Alto, CA 94304
;;; (or send Arpanet mail to [e-mail])
;;;
;;; Suggestions, comments and requests for improvements are also welcome.
;;; *************************************************************************
;;;
;;; Macros global variable definitions, and other random support stuff used
;;; by the rest of the system.
;;;
;;; For simplicity (not having to use eval-when a lot), this file must be
;;; loaded before it can be compiled.
;;;

(in-package :pcl)

(proclaim '(declaration
         #-Genera values          ;I use this so that Zwei can remind
                      ;me what values a function returns.

         #-Genera arglist          ;Tells me what the pretty arglist
                      ;of something (which probably takes
                      ;&rest args) is.

         #-Genera indentation     ;Tells ZWEI how to indent things
                          ;like defclass.
         class
         variable-rebinding
         pcl-fast-call
         method-name
         method-lambda-list
         ))

;;; Age old functions which CommonLisp cleaned-up away.  They probably exist
;;; in other packages in all CommonLisp implementations, but I will leave it
;;; to the compiler to optimize into calls to them.
;;;
;;; Common Lisp BUG:
;;;    Some Common Lisps define these in the Lisp package which causes
;;;    all sorts of lossage.  Common Lisp should explictly specify which
;;;    symbols appear in the Lisp package.
;;;
(eval-when (compile load eval)

(defmacro memq (item list) `(member ,item ,list :test #'eq))
(defmacro assq (item list) `(assoc ,item ,list :test #'eq))
(defmacro rassq (item list) `(rassoc ,item ,list :test #'eq))
(defmacro delq (item list) `(delete ,item ,list :test #'eq))
(defmacro posq (item list) `(position ,item ,list :test #'eq))
(defmacro neq (x y) `(not (eq ,x ,y)))


(defun make-caxr (n form)
  (if (< n 4)
      `(,(nth n '(car cadr caddr cadddr)) ,form)
      (make-caxr (- n 4) `(cddddr ,form))))

(defun make-cdxr (n form)
  (cond ((zerop n) form)
    ((< n 5) `(,(nth n '(identity cdr cddr cdddr cddddr)) ,form))
    (t (make-cdxr (- n 4) `(cddddr ,form)))))
)

(defun true (&rest ignore) (declare (ignore ignore)) t)
(defun false (&rest ignore) (declare (ignore ignore)) nil)
(defun zero (&rest ignore) (declare (ignore ignore)) 0)

(defun make-plist (keys vals)
  (if (null vals)
      ()
      (list* (car keys)
         (car vals)
         (make-plist (cdr keys) (cdr vals)))))

(defun remtail (list tail)
  (if (eq list tail) () (cons (car list) (remtail (cdr list) tail))))

;;; ONCE-ONLY does the same thing as it does in zetalisp.  I should have just
;;; lifted it from there but I am honest.  Not only that but this one is
;;; written in Common Lisp.  I feel a lot like bootstrapping, or maybe more
;;; like rebuilding Rome.
(defmacro once-only (vars &body body)
  (let ((gensym-var (gensym))
        (run-time-vars (gensym))
        (run-time-vals (gensym))
        (expand-time-val-forms ()))
    (dolist (var vars)
      (push `(if (or (symbolp ,var)
                     (numberp ,var)
                     (and (listp ,var)
              (member (car ,var) '(quote function))))
                 ,var
                 (let ((,gensym-var (gensym)))
                   (push ,gensym-var ,run-time-vars)
                   (push ,var ,run-time-vals)
                   ,gensym-var))
            expand-time-val-forms))
    `(let* (,run-time-vars
            ,run-time-vals
            (wrapped-body
          (let ,(mapcar #'list vars (reverse expand-time-val-forms))
        ,@body)))
       `(let ,(mapcar #'list (reverse ,run-time-vars)
                 (reverse ,run-time-vals))
      ,wrapped-body))))

(eval-when (compile load eval)
(defun extract-declarations (body &optional environment)
  ;;(declare (values documentation declarations body))
  (let (documentation declarations form)
    (when (and (stringp (car body))
           (cdr body))
      (setq documentation (pop body)))
    (block outer
      (loop
    (when (null body) (return-from outer nil))
    (setq form (car body))
    (when (block inner
        (loop (cond ((not (listp form))
                 (return-from outer nil))
                ((eq (car form) 'declare)
                 (return-from inner 't))
                (t
                 (multiple-value-bind (newform macrop)
                  (macroexpand-1 form environment)
                   (if (or (not (eq newform form)) macrop)
                   (setq form newform)
                 (return-from outer nil)))))))
      (pop body)
      (dolist (declaration (cdr form))
        (push declaration declarations)))))
    (values documentation
        (and declarations `((declare ,.(nreverse declarations))))
        body)))
)

(defun get-declaration (name declarations &optional default)
  (dolist (d declarations default)
    (dolist (form (cdr d))
      (when (and (consp form) (eq (car form) name))
    (return-from get-declaration (cdr form))))))


#+Lucid
(eval-when (compile load eval)
  (eval `(defstruct ,(intern "FASLESCAPE" (find-package 'lucid)))))

(defvar *keyword-package* (find-package 'keyword))

(defun make-keyword (symbol)
  (intern (symbol-name symbol) *keyword-package*))

(eval-when (compile load eval)

(defun string-append (&rest strings)
  (setq strings (copy-list strings))        ;The explorer can't even
                        ;rplaca an &rest arg?
  (do ((string-loc strings (cdr string-loc)))
      ((null string-loc)
       (apply #'concatenate 'string strings))
    (rplaca string-loc (string (car string-loc)))))
)

(defun symbol-append (sym1 sym2 &optional (package *package*))
  (intern (string-append sym1 sym2) package))

(defmacro check-member (place list &key (test #'eql) (pretty-name place))
  (once-only (place list)
    `(or (member ,place ,list :test ,test)
         (error "The value of ~A, ~S is not one of ~S."
                ',pretty-name ,place ,list))))

(defmacro alist-entry (alist key make-entry-fn)
  (once-only (alist key)
    `(or (assq ,key ,alist)
     (progn (setf ,alist (cons (,make-entry-fn ,key) ,alist))
        (car ,alist)))))

;;; A simple version of destructuring-bind.

;;; This does no more error checking than CAR and CDR themselves do.  Some
;;; attempt is made to be smart about preserving intermediate values.  It
;;; could be better, although the only remaining case should be easy for
;;; the compiler to spot since it compiles to PUSH POP.
;;;
;;; Common Lisp BUG:
;;;    Common Lisp should have destructuring-bind.
;;;
(defmacro destructuring-bind (pattern form &body body)
  (multiple-value-bind (ignore declares body)
      (extract-declarations body)
    (declare (ignore ignore))
    (multiple-value-bind (setqs binds)
    (destructure pattern form)
      `(let ,binds
     ,@declares
     ,@setqs
     (progn .destructure-form.)
     . ,body))))

(eval-when (compile load eval)
(defun destructure (pattern form)
  ;;(declare (values setqs binds))
  (let ((*destructure-vars* ())
    (setqs ()))
    (declare (special *destructure-vars*))
    (setq *destructure-vars* '(.destructure-form.)
      setqs (list `(setq .destructure-form. ,form))
      form '.destructure-form.)
    (values (nconc setqs (nreverse (destructure-internal pattern form)))
        (delete nil *destructure-vars*))))

(defun destructure-internal (pattern form)
  ;; When we are called, pattern must be a list.  Form should be a symbol
  ;; which we are free to setq containing the value to be destructured.
  ;; Optimizations are performed for the last element of pattern cases.
  ;; we assume that the compiler is smart about gensyms which are bound
  ;; but only for a short period of time.
  (declare (special *destructure-vars*))
  (let ((gensym (gensym))
    (pending-pops 0)
    (var nil)
    (setqs ()))
    (labels
        ((make-pop (var form pop-into)
       (prog1
         (cond ((zerop pending-pops)
            `(progn ,(and var `(setq ,var (car ,form)))
                ,(and pop-into `(setq ,pop-into (cdr ,form)))))
           ((null pop-into)
            (and var `(setq ,var ,(make-caxr pending-pops form))))
           (t
            `(progn (setq ,pop-into ,(make-cdxr pending-pops form))
                ,(and var `(setq ,var (pop ,pop-into))))))
         (setq pending-pops 0))))
      (do ((pat pattern (cdr pat)))
      ((null pat) ())
    (if (symbolp (setq var (car pat)))
        (progn
          #-:coral (unless (memq var '(nil ignore))
             (push var *destructure-vars*))
          #+:coral (push var *destructure-vars*)
          (cond ((null (cdr pat))
             (push (make-pop var form ()) setqs))
            ((symbolp (cdr pat))
             (push (make-pop var form (cdr pat)) setqs)
             (push (cdr pat) *destructure-vars*)
             (return ()))
            #-:coral
            ((memq var '(nil ignore)) (incf pending-pops))
            #-:coral
            ((memq (cadr pat) '(nil ignore))
             (push (make-pop var form ()) setqs)
             (incf pending-pops 1))
            (t
             (push (make-pop var form form) setqs))))
        (progn
          (push `(let ((,gensym ()))
               ,(make-pop gensym
                  form
                  (if (symbolp (cdr pat)) (cdr pat) form))
               ,@(nreverse
               (destructure-internal
                 (if (consp pat) (car pat) pat)
                 gensym)))
            setqs)
          (when (symbolp (cdr pat))
        (push (cdr pat) *destructure-vars*)
        (return)))))
      setqs)))
)


(defmacro collecting-once (&key initial-value)
   `(let* ((head ,initial-value)
           (tail ,(and initial-value `(last head))))
          (values #'(lambda (value)
                           (if (null head)
                               (setq head (setq tail (list value)))
                   (unless (memq value head)
                 (setq tail
                       (cdr (rplacd tail (list value)))))))
          #'(lambda nil head))))

(defmacro doplist ((key val) plist &body body &environment env)
  (multiple-value-bind (doc decls bod)
      (extract-declarations body env)
    (declare (ignore doc))
    `(let ((.plist-tail. ,plist) ,key ,val)
       ,@decls
       (loop (when (null .plist-tail.) (return nil))
         (setq ,key (pop .plist-tail.))
         (when (null .plist-tail.)
           (error "Malformed plist in doplist, odd number of elements."))
         (setq ,val (pop .plist-tail.))
         (progn ,@bod)))))

(defmacro if* (condition true &rest false)
  `(if ,condition ,true (progn ,@false)))

(defmacro dolist-carefully ((var list improper-list-handler) &body body)
  `(let ((,var nil)
         (.dolist-carefully. ,list))
     (loop (when (null .dolist-carefully.) (return nil))
           (if (consp .dolist-carefully.)
               (progn
                 (setq ,var (pop .dolist-carefully.))
                 ,@body)
               (,improper-list-handler)))))

  ;;
;;;;;; printing-random-thing
  ;;
;;; Similar to printing-random-object in the lisp machine but much simpler
;;; and machine independent.
(defmacro printing-random-thing ((thing stream) &body body)
  (once-only (stream)
  `(progn (format ,stream "#<")
      ,@body
      (format ,stream " ")
      (printing-random-thing-internal ,thing ,stream)
      (format ,stream ">"))))

(defun printing-random-thing-internal (thing stream)
  (declare (ignore thing stream))
  nil)

  ;;
;;;;;;
  ;;

(defun capitalize-words (string &optional (dashes-p t))
  (let ((string (copy-seq (string string))))
    (declare (string string))
    (do* ((flag t flag)
      (length (length string) length)
      (char nil char)
      (i 0 (+ i 1)))
     ((= i length) string)
      (setq char (elt string i))
      (cond ((both-case-p char)
         (if flag
         (and (setq flag (lower-case-p char))
              (setf (elt string i) (char-upcase char)))
         (and (not flag) (setf (elt string i) (char-downcase char))))
         (setq flag nil))
        ((char-equal char #\-)
         (setq flag t)
         (unless dashes-p (setf (elt string i) #\space)))
        (t (setq flag nil))))))

#-(or lucid kcl)
(eval-when (compile load eval)
;(warn "****** Things will go faster if you fix define-compiler-macro")
)

(defmacro define-compiler-macro (name arglist &body body)
  #+(or lucid kcl)
  `(#+lucid lcl:def-compiler-macro #+kcl si::define-compiler-macro
        ,name ,arglist
        ,@body)
  #-(or kcl lucid)
  (declare (ignore name arglist body))
  #-(or kcl lucid)
  nil)


;;;
;;; FIND-CLASS
;;;
;;; This is documented in the CLOS specification.
;;;
(defvar *find-class* (make-hash-table :test #'eq))

(defun make-constant-function (value)
  #'(lambda (object)
      (declare (ignore object))
      value))

(defun function-returning-nil (x)
  (declare (ignore x))
  nil)

(defun function-returning-t (x)
  (declare (ignore x))
  t)

(defmacro find-class-cell-class (cell)
  `(car ,cell))

(defmacro find-class-cell-predicate (cell)
  `(cadr ,cell))

(defmacro find-class-cell-make-instance-function-keys (cell)
  `(cddr ,cell))

(defmacro make-find-class-cell (class-name)
  (declare (ignore class-name))
  '(list* nil #'function-returning-nil nil))

(defun find-class-cell (symbol &optional dont-create-p)
  (or (gethash symbol *find-class*)
      (unless dont-create-p
    (unless (legal-class-name-p symbol)
      (error "~S is not a legal class name." symbol))
    (setf (gethash symbol *find-class*) (make-find-class-cell symbol)))))

(defvar *create-classes-from-internal-structure-definitions-p* t)

(defun find-class-from-cell (symbol cell &optional (errorp t))
  (or (find-class-cell-class cell)
      (and *create-classes-from-internal-structure-definitions-p*
           (structure-type-p symbol)
           (find-structure-class symbol))
      (cond ((null errorp) nil)
        ((legal-class-name-p symbol)
         (error "No class named: ~S." symbol))
        (t
         (error "~S is not a legal class name." symbol)))))

(defun find-class-predicate-from-cell (symbol cell &optional (errorp t))
  (unless (find-class-cell-class cell)
    (find-class-from-cell symbol cell errorp))
  (find-class-cell-predicate cell))

(defun legal-class-name-p (x)
  (and (symbolp x)
       (not (keywordp x))))

(defun find-class (symbol &optional (errorp t) environment)
  (declare (ignore environment))
  (find-class-from-cell
   symbol (find-class-cell symbol errorp) errorp))

(defun find-class-predicate (symbol &optional (errorp t) environment)
  (declare (ignore environment))
  (find-class-predicate-from-cell
   symbol (find-class-cell symbol errorp) errorp))

#-setf
(defsetf find-class (symbol &optional (errorp t) environment) (new-value)
  (declare (ignore errorp environment))
  `(SETF\ PCL\ FIND-CLASS ,new-value ,symbol))

(defun #-setf SETF\ PCL\ FIND-CLASS #+setf (setf find-class) (new-value symbol)
  (declare (special *boot-state*))
  (if (legal-class-name-p symbol)
      (let ((cell (find-class-cell symbol)))
    (setf (find-class-cell-class cell) new-value)
    (when (or (eq *boot-state* 'complete)
          (eq *boot-state* 'braid))
      (setf (find-class-cell-predicate cell)
        (symbol-function (class-predicate-name new-value)))
      (when (and new-value (not (forward-referenced-class-p new-value)))
        (dolist (keys+aok (find-class-cell-make-instance-function-keys cell))
          (update-initialize-info-internal
           (initialize-info new-value (car keys+aok) nil (cdr keys+aok))
           'make-instance-function)))))
      (error "~S is not a legal class name." symbol)))

#-setf
(defsetf find-class-predicate (symbol &optional (errorp t) environment) (new-value)
  (declare (ignore errorp environment))
  `(SETF\ PCL\ FIND-CLASS-PREDICATE ,new-value ,symbol))

(defun #-setf SETF\ PCL\ FIND-CLASS-PREDICATE #+setf (setf find-class-predicate)
          (new-value symbol)
  (if (legal-class-name-p symbol)
      (setf (find-class-cell-predicate (find-class-cell symbol)) new-value)
      (error "~S is not a legal class name." symbol)))

(defun find-wrapper (symbol)
  (class-wrapper (find-class symbol)))

#|| ; Anything that used this should use eval instead.
(defun reduce-constant (old)
  (let ((new (eval old)))
    (if (eq new old)
    new
    (if (constantp new)
        (reduce-constant new)
        new))))
||#

(defmacro gathering1 (gatherer &body body)
  `(gathering ((.gathering1. ,gatherer))
     (macrolet ((gather1 (x) `(gather ,x .gathering1.)))
       ,@body)))

;;;
;;;
;;;
(defmacro vectorizing (&key (size 0))
  `(let* ((limit ,size)
      (result (make-array limit))
      (index 0))
     (values #'(lambda (value)
         (if (= index limit)
             (error "vectorizing more elements than promised.")
             (progn
               (setf (svref result index) value)
               (incf index)
               value)))
         #'(lambda () result))))

;;;
;;; These are augmented definitions of list-elements and list-tails from
;;; iterate.lisp.  These versions provide the extra :by keyword which can
;;; be used to specify the step function through the list.
;;;
(defmacro *list-elements (list &key (by #'cdr))
  `(let ((tail ,list))
     #'(lambda (finish)
     (if (endp tail)
         (funcall finish)
         (prog1 (car tail)
                (setq tail (funcall ,by tail)))))))

(defmacro *list-tails (list &key (by #'cdr))
   `(let ((tail ,list))
      #'(lambda (finish)
          (prog1 (if (endp tail)
             (funcall finish)
             tail)
             (setq tail (funcall ,by tail))))))

(defmacro function-funcall (form &rest args)
  #-cmu `(funcall ,form ,@args)
  #+cmu `(funcall (the function ,form) ,@args))

(defmacro function-apply (form &rest args)
  #-cmu `(apply ,form ,@args)
  #+cmu `(apply (the function ,form) ,@args))


;;;
;;; Convert a function name to its standard setf function name.  We have to
;;; do this hack because not all Common Lisps have yet converted to having
;;; setf function specs.
;;;
;;; In a port that does have setf function specs you can use those just by
;;; making the obvious simple changes to these functions.  The rest of PCL
;;; believes that there are function names like (SETF <foo>), this is the
;;; only place that knows about this hack.
;;;
(eval-when (compile load eval)
; In 15e (and also 16c), using the built in setf mechanism costs
; a hash table lookup every time a setf function is called.
; Uncomment the next line to use the built in setf mechanism.
;#+cmu (pushnew :setf *features*)
)

(eval-when (compile load eval)

#-setf
(defvar *setf-function-names* (make-hash-table :size 200 :test #'eq))

(defun get-setf-function-name (name)
  #+setf `(setf ,name)
  #-setf
  (or (gethash name *setf-function-names*)
      (setf (gethash name *setf-function-names*)
        (let ((pkg (symbol-package name)))
          (if pkg
          (intern (format nil
                  "SETF ~A ~A"
                  (package-name pkg)
                  (symbol-name name))
              *the-pcl-package*)
          (make-symbol (format nil "SETF ~A" (symbol-name name))))))))

;;;
;;; Call this to define a setf macro for a function with the same behavior as
;;; specified by the SETF function cleanup proposal.  Specifically, this will
;;; cause: (SETF (FOO a b) x) to expand to (|SETF FOO| x a b).
;;;
;;; do-standard-defsetf                  A macro interface for use at top level
;;;                                      in files.  Unfortunately, users may
;;;                                      have to use this for a while.
;;;
;;; do-standard-defsetfs-for-defclass    A special version called by defclass.
;;;
;;; do-standard-defsetf-1                A functional interface called by the
;;;                                      above, defmethod and defgeneric.
;;;                                      Since this is all a crock anyways,
;;;                                      users are free to call this as well.
;;;
(defmacro do-standard-defsetf (&rest function-names)
  `(eval-when (compile load eval)
     (dolist (fn-name ',function-names) (do-standard-defsetf-1 fn-name))))

(defun do-standard-defsetfs-for-defclass (accessors)
  (dolist (name accessors) (do-standard-defsetf-1 name)))

(defun do-standard-defsetf-1 (function-name)
  #+setf
  (declare (ignore function-name))
  #+setf nil
  #-setf
  (unless (and (setfboundp function-name)
           (get function-name 'standard-setf))
    (setf (get function-name 'standard-setf) t)
    (let* ((setf-function-name (get-setf-function-name function-name)))

      #+Genera
      (let ((fn #'(lambda (form)
            (lt::help-defsetf
              '(&rest accessor-args) '(new-value) function-name 'nil
              `(`(,',setf-function-name ,new-value .,accessor-args))
              form))))
    (setf (get function-name 'lt::setf-method) fn
          (get function-name 'lt::setf-method-internal) fn))

      #+Lucid
      (lucid::set-simple-setf-method
    function-name
    #'(lambda (form new-value)
        (let* ((bindings (mapcar #'(lambda (x) `(,(gensym) ,x))
                     (cdr form)))
           (vars (mapcar #'car bindings)))
          ;; This may wrap spurious LET bindings around some form,
          ;;   but the PQC compiler will unwrap then.
          `(LET (,.bindings)
         (,setf-function-name ,new-value . ,vars)))))

      #+kcl
      (let ((helper (gensym)))
    (setf (macro-function helper)
          #'(lambda (form env)
          (declare (ignore env))
          (let* ((loc-args (butlast (cdr form)))
             (bindings (mapcar #'(lambda (x) `(,(gensym) ,x)) loc-args))
             (vars (mapcar #'car bindings)))
            `(let ,bindings
               (,setf-function-name ,(car (last form)) ,@vars)))))
    (eval `(defsetf ,function-name ,helper)))
      #+Xerox
      (flet ((setf-expander (body env)
           (declare (ignore env))
           (let ((temps
               (mapcar #'(lambda (x) (declare (ignore x)) (gensym))
                   (cdr body)))
             (forms (cdr body))
             (vars (list (gensym))))
         (values temps
             forms
             vars
             `(,setf-function-name ,@vars ,@temps)
             `(,function-name ,@temps)))))
    (let ((setf-method-expander (intern (concatenate 'string
                                 (symbol-name function-name)
                                 "-setf-expander")
                     (symbol-package function-name))))
      (setf (get function-name :setf-method-expander) setf-method-expander
        (symbol-function setf-method-expander) #'setf-expander)))

      #-(or Genera Lucid kcl Xerox)
      (eval `(defsetf ,function-name (&rest accessor-args) (new-value)
           (let* ((bindings (mapcar #'(lambda (x) `(,(gensym) ,x)) accessor-args))
              (vars (mapcar #'car bindings)))
          `(let ,bindings
              (,',setf-function-name ,new-value ,@vars)))))

      )))

(defun setfboundp (symbol)
  #+Genera (not (null (get-properties (symbol-plist symbol)
                      'lt::(derived-setf-function trivial-setf-method
                        setf-equivalence setf-method))))
  #+Lucid  (locally
         (declare (special lucid::*setf-inverse-table*
                   lucid::*simple-setf-method-table*
                   lucid::*setf-method-expander-table*))
         (or (gethash symbol lucid::*setf-inverse-table*)
         (gethash symbol lucid::*simple-setf-method-table*)
         (gethash symbol lucid::*setf-method-expander-table*)))
  #+kcl    (or (get symbol 'si::setf-method)
           (get symbol 'si::setf-update-fn)
           (get symbol 'si::setf-lambda))
  #+Xerox  (or (get symbol :setf-inverse)
           (get symbol 'il:setf-inverse)
           (get symbol 'il:setfn)
           (get symbol :shared-setf-inverse)
           (get symbol :setf-method-expander)
           (get symbol 'il:setf-method-expander))
  #+:coral (or (get symbol 'ccl::setf-inverse)
           (get symbol 'ccl::setf-method-expander))
  #+cmu (fboundp `(setf ,symbol))
  #-(or Genera Lucid KCL Xerox :coral cmu) nil)

);eval-when


;;;
;;; PCL, like user code, must endure the fact that we don't have a properly
;;; working setf.  Many things work because they get mentioned by a defclass
;;; or defmethod before they are used, but others have to be done by hand.
;;;
(do-standard-defsetf
  class-wrapper                                 ;***
  generic-function-name
  method-function-plist
  method-function-get
  plist-value
  object-plist
  gdefinition
  slot-value-using-class
  )

(defsetf slot-value set-slot-value)

(defvar *redefined-functions* nil)

(defmacro original-definition (name)
  `(get ,name ':definition-before-pcl))

(defun redefine-function (name new)
  (pushnew name *redefined-functions*)
  (unless (original-definition name)
    (setf (original-definition name)
      (symbol-function name)))
  (setf (symbol-function name)
    (symbol-function new)))