5 ;;; (c) 2005 Mark Wooding
8 ;;;----- Licensing notice ---------------------------------------------------
10 ;;; This program is free software; you can redistribute it and/or modify
11 ;;; it under the terms of the GNU General Public License as published by
12 ;;; the Free Software Foundation; either version 2 of the License, or
13 ;;; (at your option) any later version.
15 ;;; This program is distributed in the hope that it will be useful,
16 ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
17 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 ;;; GNU General Public License for more details.
20 ;;; You should have received a copy of the GNU General Public License
21 ;;; along with this program; if not, write to the Free Software Foundation,
22 ;;; Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
24 ;;;--------------------------------------------------------------------------
27 (defpackage #:mdw.base
29 #+cmu (:import-from #:extensions #:fixnump))
31 (in-package #:mdw.base)
33 ;;;--------------------------------------------------------------------------
36 (export 'unsigned-fixnum)
37 (deftype unsigned-fixnum ()
38 "Unsigned fixnums; useful as array indices and suchlike."
39 `(mod ,most-positive-fixnum))
41 ;;;--------------------------------------------------------------------------
42 ;;; Some simple macros to get things going.
44 (export 'compile-time-defun)
45 (defmacro compile-time-defun (name args &body body)
46 "Define a function which can be used by macros during the compilation
48 `(eval-when (:compile-toplevel :load-toplevel :execute)
49 (defun ,name ,args ,@body)))
53 "Debugging tool: print the expression X and its values."
55 `(let ((,tmp (multiple-value-list ,x)))
57 (pprint-logical-block (*standard-output* nil :per-line-prefix ";; ")
59 "~S = ~@_~:I~:[#<no values>~;~:*~{~S~^ ~_~}~]"
66 (defun stringify (str)
67 "Return a string representation of STR. Strings are returned unchanged;
68 symbols are converted to their names (unqualified!). Other objects are
69 converted to their print representations."
72 (symbol (symbol-name str))
73 (t (princ-to-string str))))
76 (defun functionify (func)
77 "Convert the function-designator FUNC to a function."
78 (declare (type (or function symbol) func))
81 (symbol (symbol-function func))))
84 (defun mappend (function list &rest more-lists)
85 "Apply FUNCTION to corresponding elements of LIST and MORE-LISTS, yielding
86 a list. Return the concatenation of all the resulting lists. Like
87 mapcan, but nondestructive."
88 (apply #'append (apply #'mapcar function list more-lists)))
91 (compile-time-defun listify (x)
92 "If X is a (possibly empty) list, return X; otherwise return (list X)."
93 (if (listp x) x (list x)))
95 (compile-time-defun do-fix-pair (x y defaultp)
96 "Helper function for fix-pair and pairify."
97 (flet ((singleton (x) (values x (if defaultp y x))))
98 (cond ((atom x) (singleton x))
99 ((null (cdr x)) (singleton (car x)))
100 ((atom (cdr x)) (values (car x) (cdr x)))
101 ((cddr x) (error "Too many elements for a pair."))
102 (t (values (car x) (cadr x))))))
105 (compile-time-defun fix-pair (x &optional (y nil defaultp))
106 "Return two values extracted from X. It works as follows:
112 where Y defaults to A if not specified."
113 (do-fix-pair x y defaultp))
116 (compile-time-defun pairify (x &optional (y nil defaultp))
117 "As for fix-pair, but returns a list instead of two values."
118 (multiple-value-call #'list (do-fix-pair x y defaultp)))
120 (export 'whitespace-char-p)
121 (defun whitespace-char-p (ch)
122 "Return whether CH is a whitespace character or not."
124 (#.(loop for i below char-code-limit
125 for ch = (code-char i)
126 unless (with-input-from-string (in (string ch))
127 (peek-char t in nil))
132 (export 'defconstant*)
133 (defmacro defconstant* (name value &key doc test)
134 "Define a constant, like `defconstant'. The TEST is an equality test used
135 to decide whether to override the current definition, if any."
136 (let ((temp (gensym)))
137 `(eval-when (:compile-toplevel :load-toplevel :execute)
138 (let ((,temp ,value))
139 (unless (and (boundp ',name)
140 (funcall ,(or test ''eql) (symbol-value ',name) ,temp))
141 (defconstant ,name ,value ,@(and doc (list doc))))
144 (export 'slot-uninitialized)
145 (declaim (ftype (function nil ()) slot-unitialized))
146 (defun slot-uninitialized ()
147 "A function which signals an error. Can be used as an initializer form in
148 structure definitions without doom ensuing."
149 (error "No initializer for slot."))
152 (compile-time-defun parse-body (body &key (allow-docstring-p t))
153 "Given a BODY (a list of forms), parses it into three sections: a
154 docstring, a list of declarations (forms beginning with the symbol
155 `declare') and the body forms. The result is returned as three lists
156 (even the docstring), suitable for interpolation into a backquoted list
157 using `@,'. If ALLOW-DOCSTRING-P is nil, docstrings aren't allowed at
159 (let ((doc nil) (decls nil))
160 (do ((forms body (cdr forms))) (nil)
161 (let ((form (and forms (car forms))))
162 (cond ((and allow-docstring-p (not doc) (stringp form) (cdr forms))
165 (eq (car form) 'declare))
166 (setf decls (append decls (cdr form))))
167 (t (return (values (and doc (list doc))
168 (and decls (list (cons 'declare decls)))
171 (export 'with-parsed-body)
172 (defmacro with-parsed-body
173 ((bodyvar declvar &optional (docvar (gensym) docp)) form &body body)
174 "Parse FORM into a body, declarations and (maybe) a docstring; bind BODYVAR
175 to the body, DECLVAR to the declarations, and DOCVAR to (a list
176 containing) the docstring, and evaluate BODY."
177 `(multiple-value-bind
178 (,docvar ,declvar ,bodyvar)
179 (parse-body ,form :allow-docstring-p ,docp)
180 ,@(if docp nil `((declare (ignore ,docvar))))
186 (declaim (inline fixnump))
187 (defun fixnump (object)
188 "Answer non-nil if OBJECT is a fixnum, or nil if it isn't."
189 (typep object 'fixnum)))
191 ;;;--------------------------------------------------------------------------
192 ;;; Generating symbols.
194 (export 'symbolicate)
195 (defun symbolicate (&rest names)
196 "Return a symbol constructued by concatenating the NAMES.
198 The NAMES are coerced to strings, using the `string' function, so they may
199 be strings, characters, or symbols. The resulting symbol is interned in
200 the current `*package*'."
201 (intern (apply #'concatenate 'string (mapcar #'string names))))
203 (export 'with-gensyms)
204 (defmacro with-gensyms (syms &body body)
205 "Everyone's favourite macro helper."
206 `(let (,@(mapcar (lambda (sym) `(,sym (gensym ,(symbol-name sym))))
210 (export 'let*/gensyms)
211 (defmacro let*/gensyms (binds &body body)
212 "A macro helper. BINDS is a list of binding pairs (VAR VALUE), where VALUE
213 defaults to VAR. The result is that BODY is evaluated in a context where
214 each VAR is bound to a gensym, and in the final expansion, each of those
215 gensyms will be bound to the corresponding VALUE."
216 (labels ((more (binds)
217 (let ((tmp (gensym "TMP")) (bind (car binds)))
218 `((let ((,tmp ,(cadr bind))
219 (,(car bind) (gensym ,(symbol-name (car bind)))))
220 `(let ((,,(car bind) ,,tmp))
226 (car (more (mapcar #'pairify (listify binds)))))))
228 ;;;--------------------------------------------------------------------------
229 ;;; Capturing places as symbols.
231 (defmacro %place-ref (getform setform newtmp)
232 "Grim helper macro for with-places."
233 (declare (ignore setform newtmp))
236 (define-setf-expander %place-ref (getform setform newtmp)
237 "Grim helper macro for with-places."
238 (values nil nil newtmp setform getform))
240 (export 'with-places)
241 (defmacro with-places (clauses &body body &environment env)
242 "Define symbols which refer to `setf'-able places.
244 The syntax is similar to `let'. The CLAUSES are a list of (NAME PLACE)
245 pairs. Each NAME is defined as a symbol-macro referring to the
246 corresponding PLACE: a mention of the NAME within the BODY forms extracts
247 the current value(s) of the PLACE, while a `setf' (or `setq', because
248 symbol macros are strange like that) of a NAME updates the value(s) in the
249 PLACE. The returned values are those of the BODY, evaluated as an
252 (let ((temp-binds nil)
254 (dolist (clause clauses)
255 (destructuring-bind (name place) clause
256 (multiple-value-bind (valtmps valforms newtmps setform getform)
257 (get-setf-expansion place env)
259 (nconc (nreverse (mapcar #'list valtmps valforms))
261 (push `(,name (%place-ref ,getform ,setform ,newtmps))
263 `(let (,@(nreverse temp-binds))
264 (symbol-macrolet (,@(nreverse macro-binds))
267 (export 'with-places/gensyms)
268 (defmacro with-places/gensyms (clauses &body body)
269 "A kind of a cross between `with-places' and `let*/gensyms'.
271 This is a hairy helper for writing `setf'-like macros. The CLAUSES are a
272 list of (NAME [PLACE]) pairs, where the PLACE defaults to NAME, and a
273 bare NAME may be written in place of the singleton list (NAME). The
274 PLACEs are evaluated.
276 The BODY forms are evaluated as an implicit `progn', with each NAME bound
277 to a gensym, to produce a Lisp form, called the `kernel'. The result of
278 the `with-places/gensyms' macro is then itself a Lisp form, called the
281 The effect of evaluating the `result' form is to evaluate the `kernel'
282 form with each of the gensyms stands for the value(s) stored in the
283 corresponding PLACE; a `setf' (or `setq') of one of the gensyms updates
284 the value(s) in the corresponding PLACE. The values returned by the
285 `result' form are the values returned by the `kernel'."
287 (let* ((clauses (mapcar #'pairify clauses))
288 (names (mapcar #'car clauses))
289 (places (mapcar #'cadr clauses))
290 (gensyms (mapcar (lambda (name) (gensym (symbol-name name)))
292 ``(with-places (,,@(mapcar (lambda (gensym place)
293 ``(,',gensym ,,place))
295 ,(let (,@(mapcar (lambda (name gensym)
300 ;;;--------------------------------------------------------------------------
301 ;;; Some simple yet useful control structures.
304 (defmacro nlet (name binds &body body)
305 "Scheme's named let."
306 (multiple-value-bind (vars vals)
307 (loop for bind in binds
308 for (var val) = (pairify bind nil)
309 collect var into vars
310 collect val into vals
311 finally (return (values vars vals)))
312 `(labels ((,name ,vars
317 (defmacro while (cond &body body)
318 "If COND is false, evaluate to nil; otherwise evaluate BODY and try again."
319 `(loop (unless ,cond (return)) (progn ,@body)))
322 (defmacro until (cond &body body)
323 "If COND is true, evaluate to nil; otherwise evaluate BODY and try again."
324 `(loop (when ,cond (return)) (progn ,@body)))
326 (compile-time-defun do-case2-like (kind vform clauses)
327 "Helper function for `case2' and `ecase2'."
328 (with-gensyms (scrutinee argument)
329 `(multiple-value-bind (,scrutinee ,argument) ,vform
330 (declare (ignorable ,argument))
332 ,@(mapcar (lambda (clause)
334 (cases (&optional varx vary) &rest forms)
338 (list `(let ((,(or vary varx) ,argument)
340 `((,varx ,scrutinee))))
346 (defmacro case2 (vform &body clauses)
347 "VFORM is a form which evaluates to two values, SCRUTINEE and ARGUMENT.
348 The CLAUSES have the form (CASES ([[SCRUVAR] ARGVAR]) FORMS...), where a
349 standard `case' clause has the form (CASES FORMS...). The `case2' form
350 evaluates the VFORM, and compares the SCRUTINEE to the various CASES, in
351 order, just like `case'. If there is a match, then the corresponding
352 FORMs are evaluated with ARGVAR bound to the ARGUMENT and SCRUVAR bound to
353 the SCRUTINEE (where specified). Note the bizarre defaulting behaviour:
354 ARGVAR is less optional than SCRUVAR."
355 (do-case2-like 'case vform clauses))
358 (defmacro ecase2 (vform &body clauses)
359 "Like `case2', but signals an error if no clause matches the SCRUTINEE."
360 (do-case2-like 'ecase vform clauses))
362 (export 'setf-default)
363 (defmacro setf-default (&rest specs)
364 "Like setf, but only sets places which are currently nil.
366 The arguments are an alternating list of PLACEs and DEFAULTs. If a PLACE
367 is nil, the DEFAULT is evaluated and stored in the PLACE; otherwise the
368 default is /not/ stored. The result is the (new) value of the last
370 `(progn ,@(do ((list nil)
371 (specs specs (cddr specs)))
372 ((endp specs) (nreverse list))
374 (error "Odd number of arguments for `setf-default'."))
375 (push (with-places/gensyms ((place (car specs)))
376 `(or ,place (setf ,place ,(cadr specs))))
379 ;;;--------------------------------------------------------------------------
380 ;;; Update-in-place macros built using with-places.
382 (export 'update-place)
383 (defmacro update-place (op place &rest args)
384 "Update PLACE with (OP PLACE . ARGS), returning the new value."
385 (with-places/gensyms (place)
386 `(setf ,place (,op ,place ,@args))))
388 (export 'update-place-after)
389 (defmacro update-place-after (op place &rest args)
390 "Update PLACE with (OP PLACE . ARGS), returning the old value."
391 (with-places/gensyms (place)
394 (setf ,place (,op ,x ,@args))
398 (defmacro incf-after (place &optional (by 1))
399 "Increment PLACE by BY, returning the old value."
400 `(update-place-after + ,place ,by))
403 (defmacro decf-after (place &optional (by 1))
404 "Decrement PLACE by BY, returning the old value."
405 `(update-place-after - ,place ,by))
407 ;;;--------------------------------------------------------------------------
411 (defstruct (loc (:predicate locp) (:constructor make-loc (reader writer)))
412 "Locative data type. See `locf' and `ref'."
413 (reader (slot-uninitialized) :type function :read-only t)
414 (writer (slot-uninitialized) :type function :read-only t))
417 (defmacro locf (place &environment env)
418 "Slightly cheesy locatives. (locf PLACE) returns an object which, using
419 the `ref' function, can be used to read or set the value of PLACE. It's
420 cheesy because it uses closures rather than actually taking the address of
421 something. Also, unlike Zetalisp, we don't overload `car' to do our dirty
424 (valtmps valforms newtmps setform getform)
425 (get-setf-expansion place env)
426 `(let* (,@(mapcar #'list valtmps valforms))
427 (make-loc (lambda () ,getform)
428 (lambda (,@newtmps) ,setform)))))
431 (declaim (inline ref (setf ref)))
433 "Fetch the value referred to by a locative."
434 (funcall (loc-reader loc)))
435 (defun (setf ref) (new loc)
436 "Store a new value in the place referred to by a locative."
437 (funcall (loc-writer loc) new))
439 (export 'with-locatives)
440 (defmacro with-locatives (locs &body body)
441 "LOCS is a list of items of the form (SYM [LOC-EXPR]), where SYM is a
442 symbol and LOC-EXPR evaluates to a locative. If LOC-EXPR is omitted, it
443 defaults to SYM. As an abbreviation for a common case, LOCS may be a
444 symbol instead of a list. The BODY is evaluated in an environment where
445 each SYM is a symbol macro which expands to (ref LOC-EXPR) -- or, in fact,
446 something similar which doesn't break if LOC-EXPR has side-effects. Thus,
447 references, including `setf' forms, fetch or modify the thing referred to
448 by the LOC-EXPR. Useful for covering over where something uses a
450 (setf locs (mapcar #'pairify (listify locs)))
451 (let ((tt (mapcar (lambda (l) (declare (ignore l)) (gensym)) locs))
452 (ll (mapcar #'cadr locs))
453 (ss (mapcar #'car locs)))
454 `(let (,@(mapcar (lambda (tmp loc) `(,tmp ,loc)) tt ll))
455 (symbol-macrolet (,@(mapcar (lambda (sym tmp)
456 `(,sym (ref ,tmp))) ss tt))
459 ;;;----- That's all, folks --------------------------------------------------