anaphora.lisp: Rewrite `asetf' to use `with-places/gensyms'.

[lisp] / mdw-base.lisp

diff --git a/mdw-base.lisp b/mdw-base.lisp
index 8ba9a24..2bad2c2 100644 (file)
--- a/mdw-base.lisp
+++ b/mdw-base.lisp
@@ -13,12 +13,12 @@
 ;;; 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.
 ;;; 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.
 ;;; 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.
 ;;; 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.


@@ -28,18 +28,6 @@
 
 (defpackage #:mdw.base
   (:use #:common-lisp)
 
 (defpackage #:mdw.base
   (:use #:common-lisp)

-  (:export #:unsigned-fixnum
-          #:compile-time-defun
-          #:show
-          #:stringify #:mappend #:listify #:fix-pair #:pairify #:parse-body
-          #:whitespace-char-p
-          #:slot-uninitialized
-          #:nlet #:while #:until #:case2 #:ecase2
-          #:with-gensyms #:let*/gensyms #:with-places
-          #:locp #:locf #:ref #:with-locatives
-          #:update-place #:update-place-after
-          #:incf-after #:decf-after
-          #:fixnump)

   #+cmu (:import-from #:extensions #:fixnump))
 
 (in-package #:mdw.base)
   #+cmu (:import-from #:extensions #:fixnump))
 
 (in-package #:mdw.base)


@@ -47,6 +35,7 @@
 ;;;--------------------------------------------------------------------------
 ;;; Useful types.
 
 ;;;--------------------------------------------------------------------------
 ;;; Useful types.
 

+(export 'unsigned-fixnum)

 (deftype unsigned-fixnum ()
   "Unsigned fixnums; useful as array indices and suchlike."
   `(mod ,most-positive-fixnum))
 (deftype unsigned-fixnum ()
   "Unsigned fixnums; useful as array indices and suchlike."
   `(mod ,most-positive-fixnum))


@@ -54,17 +43,19 @@
 ;;;--------------------------------------------------------------------------
 ;;; Some simple macros to get things going.
 
 ;;;--------------------------------------------------------------------------
 ;;; Some simple macros to get things going.
 

+(export 'compile-time-defun)

 (defmacro compile-time-defun (name args &body body)
   "Define a function which can be used by macros during the compilation
    process."
 (defmacro compile-time-defun (name args &body body)
   "Define a function which can be used by macros during the compilation
    process."

-  `(eval-when (:compile-toplevel :load-toplevel)
+  `(eval-when (:compile-toplevel :load-toplevel :execute)

      (defun ,name ,args ,@body)))
 
      (defun ,name ,args ,@body)))
 

+(export 'show)

 (defmacro show (x)
   "Debugging tool: print the expression X and its values."
   (let ((tmp (gensym)))
     `(let ((,tmp (multiple-value-list ,x)))
 (defmacro show (x)
   "Debugging tool: print the expression X and its values."
   (let ((tmp (gensym)))
     `(let ((,tmp (multiple-value-list ,x)))

-       (format t "~&")
+       (fresh-line)

        (pprint-logical-block (*standard-output* nil :per-line-prefix ";; ")
         (format t
                 "~S = ~@_~:I~:[#<no values>~;~:*~{~S~^ ~_~}~]"
        (pprint-logical-block (*standard-output* nil :per-line-prefix ";; ")
         (format t
                 "~S = ~@_~:I~:[#<no values>~;~:*~{~S~^ ~_~}~]"


@@ -73,6 +64,7 @@
        (terpri)
        (values-list ,tmp))))
 
        (terpri)
        (values-list ,tmp))))
 

+(export 'stringify)

 (defun stringify (str)
   "Return a string representation of STR.  Strings are returned unchanged;
    symbols are converted to their names (unqualified!).  Other objects are
 (defun stringify (str)
   "Return a string representation of STR.  Strings are returned unchanged;
    symbols are converted to their names (unqualified!).  Other objects are


@@ -80,15 +72,24 @@
   (typecase str
     (string str)
     (symbol (symbol-name str))
   (typecase str
     (string str)
     (symbol (symbol-name str))

-    (t (with-output-to-string (s)
-        (princ str s)))))
+    (t (princ-to-string str))))

 
 

+(export 'functionify)
+(defun functionify (func)
+  "Convert the function-designator FUNC to a function."
+  (declare (type (or function symbol) func))
+  (etypecase func
+    (function func)
+    (symbol (symbol-function func))))
+
+(export 'mappend)

 (defun mappend (function list &rest more-lists)
   "Apply FUNCTION to corresponding elements of LIST and MORE-LISTS, yielding
    a list.  Return the concatenation of all the resulting lists.  Like
    mapcan, but nondestructive."
   (apply #'append (apply #'mapcar function list more-lists)))
 
 (defun mappend (function list &rest more-lists)
   "Apply FUNCTION to corresponding elements of LIST and MORE-LISTS, yielding
    a list.  Return the concatenation of all the resulting lists.  Like
    mapcan, but nondestructive."
   (apply #'append (apply #'mapcar function list more-lists)))
 

+(export 'listify)

 (compile-time-defun listify (x)
   "If X is a (possibly empty) list, return X; otherwise return (list X)."
   (if (listp x) x (list x)))
 (compile-time-defun listify (x)
   "If X is a (possibly empty) list, return X; otherwise return (list X)."
   (if (listp x) x (list x)))


@@ -102,6 +103,7 @@
          ((cddr x) (error "Too many elements for a pair."))
          (t (values (car x) (cadr x))))))
 
          ((cddr x) (error "Too many elements for a pair."))
          (t (values (car x) (cadr x))))))
 

+(export 'fix-pair)

 (compile-time-defun fix-pair (x &optional (y nil defaultp))
   "Return two values extracted from X.  It works as follows:
      (A) -> A, Y
 (compile-time-defun fix-pair (x &optional (y nil defaultp))
   "Return two values extracted from X.  It works as follows:
      (A) -> A, Y


@@ -112,24 +114,43 @@
    where Y defaults to A if not specified."
   (do-fix-pair x y defaultp))
 
    where Y defaults to A if not specified."
   (do-fix-pair x y defaultp))
 

+(export 'pairify)

 (compile-time-defun pairify (x &optional (y nil defaultp))
   "As for fix-pair, but returns a list instead of two values."
   (multiple-value-call #'list (do-fix-pair x y defaultp)))
 
 (compile-time-defun pairify (x &optional (y nil defaultp))
   "As for fix-pair, but returns a list instead of two values."
   (multiple-value-call #'list (do-fix-pair x y defaultp)))
 

+(export 'whitespace-char-p)

 (defun whitespace-char-p (ch)
   "Return whether CH is a whitespace character or not."
   (case ch
 (defun whitespace-char-p (ch)
   "Return whether CH is a whitespace character or not."
   (case ch

-    ((#\space #\tab #\newline #\return #\vt
-             #+cmu #\formfeed
-             #+clisp #\page) t)
+    (#.(loop for i below char-code-limit
+            for ch = (code-char i)
+            unless (with-input-from-string (in (string ch))
+                     (peek-char t in nil))
+            collect ch)
+       t)

     (t nil)))
 
     (t nil)))
 

+(export 'defconstant*)
+(defmacro defconstant* (name value &key doc test)
+  "Define a constant, like `defconstant'.  The TEST is an equality test used
+   to decide whether to override the current definition, if any."
+  (let ((temp (gensym)))
+    `(eval-when (:compile-toplevel :load-toplevel :execute)
+       (let ((,temp ,value))
+        (unless (and (boundp ',name)
+                     (funcall ,(or test ''eql) (symbol-value ',name) ,temp))
+          (defconstant ,name ,value ,@(and doc (list doc))))
+        ',name))))
+
+(export 'slot-uninitialized)

 (declaim (ftype (function nil ()) slot-unitialized))
 (defun slot-uninitialized ()
   "A function which signals an error.  Can be used as an initializer form in
    structure definitions without doom ensuing."
   (error "No initializer for slot."))
 
 (declaim (ftype (function nil ()) slot-unitialized))
 (defun slot-uninitialized ()
   "A function which signals an error.  Can be used as an initializer form in
    structure definitions without doom ensuing."
   (error "No initializer for slot."))
 

+(export 'parse-body)

 (compile-time-defun parse-body (body &key (allow-docstring-p t))
   "Given a BODY (a list of forms), parses it into three sections: a
    docstring, a list of declarations (forms beginning with the symbol
 (compile-time-defun parse-body (body &key (allow-docstring-p t))
   "Given a BODY (a list of forms), parses it into three sections: a
    docstring, a list of declarations (forms beginning with the symbol


@@ -149,6 +170,19 @@
                                 (and decls (list (cons 'declare decls)))
                                 forms))))))))
 
                                 (and decls (list (cons 'declare decls)))
                                 forms))))))))
 

+(export 'with-parsed-body)
+(defmacro with-parsed-body
+    ((bodyvar declvar &optional (docvar (gensym) docp)) form &body body)
+  "Parse FORM into a body, declarations and (maybe) a docstring; bind BODYVAR
+   to the body, DECLVAR to the declarations, and DOCVAR to (a list
+   containing) the docstring, and evaluate BODY."
+  `(multiple-value-bind
+       (,docvar ,declvar ,bodyvar)
+       (parse-body ,form :allow-docstring-p ,docp)
+     ,@(if docp nil `((declare (ignore ,docvar))))
+     ,@body))
+
+(export 'fixnump)

 #-cmu
 (progn
   (declaim (inline fixnump))
 #-cmu
 (progn
   (declaim (inline fixnump))


@@ -159,32 +193,107 @@
 ;;;--------------------------------------------------------------------------
 ;;; Generating symbols.
 
 ;;;--------------------------------------------------------------------------
 ;;; Generating symbols.
 

+(export 'with-gensyms)

 (defmacro with-gensyms (syms &body body)
   "Everyone's favourite macro helper."
   `(let (,@(mapcar (lambda (sym) `(,sym (gensym ,(symbol-name sym))))
 (defmacro with-gensyms (syms &body body)
   "Everyone's favourite macro helper."
   `(let (,@(mapcar (lambda (sym) `(,sym (gensym ,(symbol-name sym))))

-                   (listify syms)))
+                  (listify syms)))

      ,@body))
 
      ,@body))
 

+(export 'let*/gensyms)

 (defmacro let*/gensyms (binds &body body)
   "A macro helper.  BINDS is a list of binding pairs (VAR VALUE), where VALUE
    defaults to VAR.  The result is that BODY is evaluated in a context where
    each VAR is bound to a gensym, and in the final expansion, each of those
    gensyms will be bound to the corresponding VALUE."
   (labels ((more (binds)
 (defmacro let*/gensyms (binds &body body)
   "A macro helper.  BINDS is a list of binding pairs (VAR VALUE), where VALUE
    defaults to VAR.  The result is that BODY is evaluated in a context where
    each VAR is bound to a gensym, and in the final expansion, each of those
    gensyms will be bound to the corresponding VALUE."
   (labels ((more (binds)

-             (let ((tmp (gensym "TMP")) (bind (car binds)))
-               `((let ((,tmp ,(cadr bind))
-                       (,(car bind) (gensym ,(symbol-name (car bind)))))
-                   `(let ((,,(car bind) ,,tmp))
-                      ,,@(if (cdr binds)
-                             (more (cdr binds))
-                             body)))))))
+            (let ((tmp (gensym "TMP")) (bind (car binds)))
+              `((let ((,tmp ,(cadr bind))
+                      (,(car bind) (gensym ,(symbol-name (car bind)))))
+                  `(let ((,,(car bind) ,,tmp))
+                     ,,@(if (cdr binds)
+                            (more (cdr binds))
+                            body)))))))

     (if (null binds)
     (if (null binds)

-        `(progn ,@body)
-        (car (more (mapcar #'pairify (listify binds)))))))
+       `(progn ,@body)
+       (car (more (mapcar #'pairify (listify binds)))))))
+
+;;;--------------------------------------------------------------------------
+;;; Capturing places as symbols.
+
+(defmacro %place-ref (getform setform newtmp)
+  "Grim helper macro for with-places."
+  (declare (ignore setform newtmp))
+  getform)
+
+(define-setf-expander %place-ref (getform setform newtmp)
+  "Grim helper macro for with-places."
+  (values nil nil newtmp setform getform))
+
+(export 'with-places)
+(defmacro with-places (clauses &body body &environment env)
+  "Define symbols which refer to `setf'-able places.
+
+   The syntax is similar to `let'.  The CLAUSES are a list of (NAME PLACE)
+   pairs.  Each NAME is defined as a symbol-macro referring to the
+   corresponding PLACE: a mention of the NAME within the BODY forms extracts
+   the current value(s) of the PLACE, while a `setf' (or `setq', because
+   symbol macros are strange like that) of a NAME updates the value(s) in the
+   PLACE.  The returned values are those of the BODY, evaluated as an
+   implicit `progn'."
+
+  (let ((temp-binds nil)
+       (macro-binds nil))
+    (dolist (clause clauses)
+      (destructuring-bind (name place) clause
+       (multiple-value-bind (valtmps valforms newtmps setform getform)
+           (get-setf-expansion place env)
+         (setf temp-binds
+               (nconc (nreverse (mapcar #'list valtmps valforms))
+                      temp-binds))
+         (push `(,name (%place-ref ,getform ,setform ,newtmps))
+               macro-binds))))
+    `(let (,@(nreverse temp-binds))
+       (symbol-macrolet (,@(nreverse macro-binds))
+        ,@body))))
+
+(export 'with-places/gensyms)
+(defmacro with-places/gensyms (clauses &body body)
+  "A kind of a cross between `with-places' and `let*/gensyms'.
+
+   This is a hairy helper for writing `setf'-like macros.  The CLAUSES are a
+   list of (NAME [PLACE]) pairs, where the PLACE defaults to NAME, and a
+   bare NAME may be written in place of the singleton list (NAME).  The
+   PLACEs are evaluated.
+
+   The BODY forms are evaluated as an implicit `progn', with each NAME bound
+   to a gensym, to produce a Lisp form, called the `kernel'.  The result of
+   the `with-places/gensyms' macro is then itself a Lisp form, called the
+   `result'.
+
+   The effect of evaluating the `result' form is to evaluate the `kernel'
+   form with each of the gensyms stands for the value(s) stored in the
+   corresponding PLACE; a `setf' (or `setq') of one of the gensyms updates
+   the value(s) in the corresponding PLACE.  The values returned by the
+   `result' form are the values returned by the `kernel'."
+
+  (let* ((clauses (mapcar #'pairify clauses))
+        (names (mapcar #'car clauses))
+        (places (mapcar #'cadr clauses))
+        (gensyms (mapcar (lambda (name) (gensym (symbol-name name)))
+                         names)))
+    ``(with-places (,,@(mapcar (lambda (gensym place)
+                                ``(,',gensym ,,place))
+                              gensyms places))
+       ,(let (,@(mapcar (lambda (name gensym)
+                          `(,name ',gensym))
+                        names gensyms))
+          ,@body))))

 
 ;;;--------------------------------------------------------------------------
 ;;; Some simple yet useful control structures.
 
 
 ;;;--------------------------------------------------------------------------
 ;;; Some simple yet useful control structures.
 

+(export 'nlet)

 (defmacro nlet (name binds &body body)
   "Scheme's named let."
   (multiple-value-bind (vars vals)
 (defmacro nlet (name binds &body body)
   "Scheme's named let."
   (multiple-value-bind (vars vals)


@@ -194,13 +303,15 @@
            collect val into vals
            finally (return (values vars vals)))
     `(labels ((,name ,vars
            collect val into vals
            finally (return (values vars vals)))
     `(labels ((,name ,vars

-               ,@body))
+               ,@body))

        (,name ,@vals))))
 
        (,name ,@vals))))
 

+(export 'while)

 (defmacro while (cond &body body)
   "If COND is false, evaluate to nil; otherwise evaluate BODY and try again."
   `(loop (unless ,cond (return)) (progn ,@body)))
 
 (defmacro while (cond &body body)
   "If COND is false, evaluate to nil; otherwise evaluate BODY and try again."
   `(loop (unless ,cond (return)) (progn ,@body)))
 

+(export 'until)

 (defmacro until (cond &body body)
   "If COND is true, evaluate to nil; otherwise evaluate BODY and try again."
   `(loop (when ,cond (return)) (progn ,@body)))
 (defmacro until (cond &body body)
   "If COND is true, evaluate to nil; otherwise evaluate BODY and try again."
   `(loop (when ,cond (return)) (progn ,@body)))


@@ -220,10 +331,11 @@
                               (list `(let ((,(or vary varx) ,argument)
                                            ,@(and vary
                                                   `((,varx ,scrutinee))))
                               (list `(let ((,(or vary varx) ,argument)
                                            ,@(and vary
                                                   `((,varx ,scrutinee))))

-                                       ,@forms))
+                                       ,@forms))

                               forms))))
                   clauses)))))
 
                               forms))))
                   clauses)))))
 

+(export 'caase2)

 (defmacro case2 (vform &body clauses)
   "VFORM is a form which evaluates to two values, SCRUTINEE and ARGUMENT.
    The CLAUSES have the form (CASES ([[SCRUVAR] ARGVAR]) FORMS...), where a
 (defmacro case2 (vform &body clauses)
   "VFORM is a form which evaluates to two values, SCRUTINEE and ARGUMENT.
    The CLAUSES have the form (CASES ([[SCRUVAR] ARGVAR]) FORMS...), where a


@@ -235,75 +347,52 @@
    ARGVAR is less optional than SCRUVAR."
   (do-case2-like 'case vform clauses))
 
    ARGVAR is less optional than SCRUVAR."
   (do-case2-like 'case vform clauses))
 

+(export 'ecase2)

 (defmacro ecase2 (vform &body clauses)
   "Like `case2', but signals an error if no clause matches the SCRUTINEE."
   (do-case2-like 'ecase vform clauses))
 
 (defmacro ecase2 (vform &body clauses)
   "Like `case2', but signals an error if no clause matches the SCRUTINEE."
   (do-case2-like 'ecase vform clauses))
 

-;;;--------------------------------------------------------------------------
-;;; with-places
-
-(defmacro %place-ref (getform setform newtmp)
-  "Grim helper macro for with-places."
-  (declare (ignore setform newtmp))
-  getform)
-
-(define-setf-expander %place-ref (getform setform newtmp)
-  "Grim helper macro for with-places."
-  (values nil nil newtmp setform getform))
-
-(defmacro with-places ((&key environment) places &body body)
-  "A hairy helper, for writing setf-like macros.  PLACES is a list of binding
-   pairs (VAR PLACE), where PLACE defaults to VAR.  The result is that BODY
-   is evaluated in a context where each VAR is bound to a gensym, and in the
-   final expansion, each of those gensyms will be bound to a symbol-macro
-   capable of reading or setting the value of the corresponding PLACE."
-  (if (null places)
-      `(progn ,@body)
-      (let*/gensyms (environment)
-        (labels
-            ((more (places)
-               (let ((place (car places)))
-                 (with-gensyms (tmp valtmps valforms
-                                    newtmps setform getform)
-                   `((let ((,tmp ,(cadr place))
-                           (,(car place)
-                            (gensym ,(symbol-name (car place)))))
-                       (multiple-value-bind
-                           (,valtmps ,valforms
-                            ,newtmps ,setform ,getform)
-                           (get-setf-expansion ,tmp
-                                               ,environment)
-                         (list 'let*
-                               (mapcar #'list ,valtmps ,valforms)
-                               `(symbol-macrolet ((,,(car place)
-                                                   (%place-ref ,,getform
-                                                               ,,setform
-                                                               ,,newtmps)))
-                                  ,,@(if (cdr places)
-                                         (more (cdr places))
-                                         body))))))))))
-          (car (more (mapcar #'pairify (listify places))))))))
+(export 'setf-default)
+(defmacro setf-default (&rest specs)
+  "Like setf, but only sets places which are currently nil.
+
+   The arguments are an alternating list of PLACEs and DEFAULTs.  If a PLACE
+   is nil, the DEFAULT is evaluated and stored in the PLACE; otherwise the
+   default is /not/ stored.  The result is the (new) value of the last
+   PLACE."
+  `(progn ,@(do ((list nil)
+                (specs specs (cddr specs)))
+               ((endp specs) (nreverse list))
+             (unless (cdr specs)
+               (error "Odd number of arguments for `setf-default'."))
+             (push (with-places/gensyms ((place (car specs)))
+                     `(or ,place (setf ,place ,(cadr specs))))
+                   list))))

 
 ;;;--------------------------------------------------------------------------
 ;;; Update-in-place macros built using with-places.
 
 
 ;;;--------------------------------------------------------------------------
 ;;; Update-in-place macros built using with-places.
 

-(defmacro update-place (op place arg &environment env)
-  "Update PLACE with the value of OP PLACE ARG, returning the new value."
-  (with-places (:environment env) (place)
-    `(setf ,place (,op ,place ,arg))))
+(export 'update-place)
+(defmacro update-place (op place &rest args)
+  "Update PLACE with (OP PLACE . ARGS), returning the new value."
+  (with-places/gensyms (place)
+    `(setf ,place (,op ,place ,@args))))

 
 

-(defmacro update-place-after (op place arg &environment env)
-  "Update PLACE with the value of OP PLACE ARG, returning the old value."
-  (with-places (:environment env) (place)
+(export 'update-place-after)
+(defmacro update-place-after (op place &rest args)
+  "Update PLACE with (OP PLACE . ARGS), returning the old value."
+  (with-places/gensyms (place)

     (with-gensyms (x)
       `(let ((,x ,place))
     (with-gensyms (x)
       `(let ((,x ,place))

-        (setf ,place (,op ,x ,arg))
+        (setf ,place (,op ,x ,@args))

         ,x))))
 
         ,x))))
 

+(export 'incf-after)

 (defmacro incf-after (place &optional (by 1))
   "Increment PLACE by BY, returning the old value."
   `(update-place-after + ,place ,by))
 
 (defmacro incf-after (place &optional (by 1))
   "Increment PLACE by BY, returning the old value."
   `(update-place-after + ,place ,by))
 

+(export 'decf-after)

 (defmacro decf-after (place &optional (by 1))
   "Decrement PLACE by BY, returning the old value."
   `(update-place-after - ,place ,by))
 (defmacro decf-after (place &optional (by 1))
   "Decrement PLACE by BY, returning the old value."
   `(update-place-after - ,place ,by))


@@ -311,11 +400,13 @@
 ;;;--------------------------------------------------------------------------
 ;;; Locatives.
 
 ;;;--------------------------------------------------------------------------
 ;;; Locatives.
 

+(export 'locp)

 (defstruct (loc (:predicate locp) (:constructor make-loc (reader writer)))
   "Locative data type.  See `locf' and `ref'."
 (defstruct (loc (:predicate locp) (:constructor make-loc (reader writer)))
   "Locative data type.  See `locf' and `ref'."

-  (reader (slot-uninitialized) :type function)
-  (writer (slot-uninitialized) :type function))
+  (reader (slot-uninitialized) :type function :read-only t)
+  (writer (slot-uninitialized) :type function :read-only t))

 
 

+(export 'locf)

 (defmacro locf (place &environment env)
   "Slightly cheesy locatives.  (locf PLACE) returns an object which, using
    the `ref' function, can be used to read or set the value of PLACE.  It's
 (defmacro locf (place &environment env)
   "Slightly cheesy locatives.  (locf PLACE) returns an object which, using
    the `ref' function, can be used to read or set the value of PLACE.  It's


@@ -327,18 +418,18 @@
       (get-setf-expansion place env)
     `(let* (,@(mapcar #'list valtmps valforms))
        (make-loc (lambda () ,getform)
       (get-setf-expansion place env)
     `(let* (,@(mapcar #'list valtmps valforms))
        (make-loc (lambda () ,getform)

-                 (lambda (,@newtmps) ,setform)))))
-
-(declaim (inline loc (setf loc)))
+                (lambda (,@newtmps) ,setform)))))

 
 

+(export 'ref)
+(declaim (inline ref (setf ref)))

 (defun ref (loc)
   "Fetch the value referred to by a locative."
   (funcall (loc-reader loc)))
 (defun ref (loc)
   "Fetch the value referred to by a locative."
   (funcall (loc-reader loc)))

-

 (defun (setf ref) (new loc)
   "Store a new value in the place referred to by a locative."
   (funcall (loc-writer loc) new))
 
 (defun (setf ref) (new loc)
   "Store a new value in the place referred to by a locative."
   (funcall (loc-writer loc) new))
 

+(export 'with-locatives)

 (defmacro with-locatives (locs &body body)
   "LOCS is a list of items of the form (SYM [LOC-EXPR]), where SYM is a
    symbol and LOC-EXPR evaluates to a locative.  If LOC-EXPR is omitted, it
 (defmacro with-locatives (locs &body body)
   "LOCS is a list of items of the form (SYM [LOC-EXPR]), where SYM is a
    symbol and LOC-EXPR evaluates to a locative.  If LOC-EXPR is omitted, it