mdw-base.lisp: Rewrite `setf-default' using `with-places/gensyms'.

[lisp] / mdw-base.lisp

diff --git a/mdw-base.lisp b/mdw-base.lisp
index a5b154b..2bad2c2 100644 (file)
--- a/mdw-base.lisp
+++ b/mdw-base.lisp
@@ -28,20 +28,6 @@
 
 (defpackage #:mdw.base
   (:use #:common-lisp)
 
 (defpackage #:mdw.base
   (:use #:common-lisp)

-  (:export #:unsigned-fixnum
-          #:compile-time-defun
-          #:show
-          #:stringify #:functionify #:mappend
-          #:listify #:fix-pair #:pairify
-          #:parse-body #:with-parsed-body
-          #:whitespace-char-p
-          #:slot-uninitialized
-          #:nlet #:while #:until #:case2 #:ecase2 #:setf-default
-          #: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)


@@ -49,6 +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))


@@ -56,12 +43,14 @@
 ;;;--------------------------------------------------------------------------
 ;;; 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."
   `(eval-when (:compile-toplevel :load-toplevel :execute)
      (defun ,name ,args ,@body)))
 
 (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 :execute)
      (defun ,name ,args ,@body)))
 

+(export 'show)

 (defmacro show (x)
   "Debugging tool: print the expression X and its values."
   (let ((tmp (gensym)))
 (defmacro show (x)
   "Debugging tool: print the expression X and its values."
   (let ((tmp (gensym)))


@@ -75,6 +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


@@ -84,6 +74,7 @@
     (symbol (symbol-name str))
     (t (princ-to-string str))))
 
     (symbol (symbol-name str))
     (t (princ-to-string str))))
 

+(export 'functionify)

 (defun functionify (func)
   "Convert the function-designator FUNC to a function."
   (declare (type (or function symbol) func))
 (defun functionify (func)
   "Convert the function-designator FUNC to a function."
   (declare (type (or function symbol) func))


@@ -91,12 +82,14 @@
     (function func)
     (symbol (symbol-function 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)))


@@ -110,6 +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


@@ -120,10 +114,12 @@
    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


@@ -135,6 +131,7 @@
        t)
     (t nil)))
 
        t)
     (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."
 (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."


@@ -146,12 +143,14 @@
           (defconstant ,name ,value ,@(and doc (list doc))))
         ',name))))
 
           (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


@@ -171,6 +170,7 @@
                                 (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
 (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


@@ -182,6 +182,7 @@
      ,@(if docp nil `((declare (ignore ,docvar))))
      ,@body))
 
      ,@(if docp nil `((declare (ignore ,docvar))))
      ,@body))
 

+(export 'fixnump)

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


@@ -192,12 +193,14 @@
 ;;;--------------------------------------------------------------------------
 ;;; 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))))
                   (listify syms)))
      ,@body))
 
 (defmacro with-gensyms (syms &body body)
   "Everyone's favourite macro helper."
   `(let (,@(mapcar (lambda (sym) `(,sym (gensym ,(symbol-name sym))))
                   (listify syms)))
      ,@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
 (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


@@ -216,88 +219,6 @@
        (car (more (mapcar #'pairify (listify binds)))))))
 
 ;;;--------------------------------------------------------------------------
        (car (more (mapcar #'pairify (listify binds)))))))
 
 ;;;--------------------------------------------------------------------------

-;;; Some simple yet useful control structures.
-
-(defmacro nlet (name binds &body body)
-  "Scheme's named let."
-  (multiple-value-bind (vars vals)
-      (loop for bind in binds
-           for (var val) = (pairify bind nil)
-           collect var into vars
-           collect val into vals
-           finally (return (values vars vals)))
-    `(labels ((,name ,vars
-               ,@body))
-       (,name ,@vals))))
-
-(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 until (cond &body body)
-  "If COND is true, evaluate to nil; otherwise evaluate BODY and try again."
-  `(loop (when ,cond (return)) (progn ,@body)))
-
-(compile-time-defun do-case2-like (kind vform clauses)
-  "Helper function for `case2' and `ecase2'."
-  (with-gensyms (scrutinee argument)
-    `(multiple-value-bind (,scrutinee ,argument) ,vform
-       (declare (ignorable ,argument))
-       (,kind ,scrutinee
-        ,@(mapcar (lambda (clause)
-                    (destructuring-bind
-                        (cases (&optional varx vary) &rest forms)
-                        clause
-                      `(,cases
-                        ,@(if varx
-                              (list `(let ((,(or vary varx) ,argument)
-                                           ,@(and vary
-                                                  `((,varx ,scrutinee))))
-                                       ,@forms))
-                              forms))))
-                  clauses)))))
-
-(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
-   standard `case' clause has the form (CASES FORMS...).  The `case2' form
-   evaluates the VFORM, and compares the SCRUTINEE to the various CASES, in
-   order, just like `case'.  If there is a match, then the corresponding
-   FORMs are evaluated with ARGVAR bound to the ARGUMENT and SCRUVAR bound to
-   the SCRUTINEE (where specified).  Note the bizarre defaulting behaviour:
-   ARGVAR is less optional than SCRUVAR."
-  (do-case2-like 'case 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))
-
-(defmacro setf-default (&rest specs &environment env)
-  "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."
-  (labels ((doit (specs)
-            (cond ((null specs) nil)
-                  ((null (cdr specs))
-                   (error "Odd number of arguments for SETF-DEFAULT."))
-                  (t
-                   (let ((place (car specs))
-                         (default (cadr specs))
-                         (rest (cddr specs)))
-                     (multiple-value-bind
-                         (vars vals store-vals writer reader)
-                         (get-setf-expansion place env)
-                       `(let* ,(mapcar #'list vars vals)
-                          (or ,reader
-                              (multiple-value-bind ,store-vals ,default
-                                ,writer))
-                          ,@(and rest (list (doit rest))))))))))
-    (doit specs)))
-
-;;;--------------------------------------------------------------------------

 ;;; Capturing places as symbols.
 
 (defmacro %place-ref (getform setform newtmp)
 ;;; Capturing places as symbols.
 
 (defmacro %place-ref (getform setform newtmp)


@@ -309,6 +230,7 @@
   "Grim helper macro for with-places."
   (values nil nil newtmp setform getform))
 
   "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.
 
 (defmacro with-places (clauses &body body &environment env)
   "Define symbols which refer to `setf'-able places.
 


@@ -335,6 +257,7 @@
        (symbol-macrolet (,@(nreverse macro-binds))
         ,@body))))
 
        (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'.
 
 (defmacro with-places/gensyms (clauses &body body)
   "A kind of a cross between `with-places' and `let*/gensyms'.
 


@@ -368,13 +291,94 @@
           ,@body))))
 
 ;;;--------------------------------------------------------------------------
           ,@body))))
 
 ;;;--------------------------------------------------------------------------

+;;; Some simple yet useful control structures.
+
+(export 'nlet)
+(defmacro nlet (name binds &body body)
+  "Scheme's named let."
+  (multiple-value-bind (vars vals)
+      (loop for bind in binds
+           for (var val) = (pairify bind nil)
+           collect var into vars
+           collect val into vals
+           finally (return (values vars vals)))
+    `(labels ((,name ,vars
+               ,@body))
+       (,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)))
+
+(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)))
+
+(compile-time-defun do-case2-like (kind vform clauses)
+  "Helper function for `case2' and `ecase2'."
+  (with-gensyms (scrutinee argument)
+    `(multiple-value-bind (,scrutinee ,argument) ,vform
+       (declare (ignorable ,argument))
+       (,kind ,scrutinee
+        ,@(mapcar (lambda (clause)
+                    (destructuring-bind
+                        (cases (&optional varx vary) &rest forms)
+                        clause
+                      `(,cases
+                        ,@(if varx
+                              (list `(let ((,(or vary varx) ,argument)
+                                           ,@(and vary
+                                                  `((,varx ,scrutinee))))
+                                       ,@forms))
+                              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
+   standard `case' clause has the form (CASES FORMS...).  The `case2' form
+   evaluates the VFORM, and compares the SCRUTINEE to the various CASES, in
+   order, just like `case'.  If there is a match, then the corresponding
+   FORMs are evaluated with ARGVAR bound to the ARGUMENT and SCRUVAR bound to
+   the SCRUTINEE (where specified).  Note the bizarre defaulting behaviour:
+   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))
+
+(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.
 

+(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 (op place &rest args)
   "Update PLACE with (OP PLACE . ARGS), returning the new value."
   (with-places/gensyms (place)
     `(setf ,place (,op ,place ,@args))))
 

+(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)
 (defmacro update-place-after (op place &rest args)
   "Update PLACE with (OP PLACE . ARGS), returning the old value."
   (with-places/gensyms (place)


@@ -383,10 +387,12 @@
         (setf ,place (,op ,x ,@args))
         ,x))))
 
         (setf ,place (,op ,x ,@args))
         ,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))


@@ -394,11 +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


@@ -412,16 +420,16 @@
        (make-loc (lambda () ,getform)
                 (lambda (,@newtmps) ,setform)))))
 
        (make-loc (lambda () ,getform)
                 (lambda (,@newtmps) ,setform)))))
 

-(declaim (inline loc (setf loc)))
-
+(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