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861345b4 | 1 | ;;; -*-lisp-*- |
2 | ;;; | |
3 | ;;; $Id$ | |
4 | ;;; | |
5 | ;;; Basic definitions | |
6 | ;;; | |
7 | ;;; (c) 2005 Mark Wooding | |
8 | ;;; | |
9 | ||
10 | ;;;----- Licensing notice --------------------------------------------------- | |
11 | ;;; | |
12 | ;;; This program is free software; you can redistribute it and/or modify | |
13 | ;;; it under the terms of the GNU General Public License as published by | |
14 | ;;; the Free Software Foundation; either version 2 of the License, or | |
15 | ;;; (at your option) any later version. | |
16 | ;;; | |
17 | ;;; This program is distributed in the hope that it will be useful, | |
18 | ;;; but WITHOUT ANY WARRANTY; without even the implied warranty of | |
19 | ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
20 | ;;; GNU General Public License for more details. | |
21 | ;;; | |
22 | ;;; You should have received a copy of the GNU General Public License | |
23 | ;;; along with this program; if not, write to the Free Software Foundation, | |
24 | ;;; Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
25 | ||
02866e07 MW |
26 | ;;;-------------------------------------------------------------------------- |
27 | ;;; Package things. | |
28 | ||
861345b4 | 29 | (defpackage #:mdw.base |
30 | (:use #:common-lisp) | |
31 | (:export #:compile-time-defun | |
32 | #:show | |
9d3ccec7 | 33 | #:stringify #:listify #:fix-pair #:pairify #:parse-body |
861345b4 | 34 | #:whitespace-char-p |
35 | #:slot-uninitialized | |
560e1186 | 36 | #:nlet #:while #:case2 #:ecase2 |
861345b4 | 37 | #:with-gensyms #:let*/gensyms #:with-places |
e979e568 MW |
38 | #:locp #:locf #:ref #:with-locatives |
39 | #:update-place #:update-place-after | |
40 | #:incf-after #:decf-after)) | |
861345b4 | 41 | (in-package #:mdw.base) |
42 | ||
02866e07 MW |
43 | ;;;-------------------------------------------------------------------------- |
44 | ;;; Some simple macros to get things going. | |
45 | ||
861345b4 | 46 | (defmacro compile-time-defun (name args &body body) |
47 | "Define a function which can be used by macros during the compilation | |
48 | process." | |
49 | `(eval-when (:compile-toplevel :load-toplevel) | |
50 | (defun ,name ,args ,@body))) | |
51 | ||
52 | (defmacro show (x) | |
53 | "Debugging tool: print the expression X and its value." | |
54 | (let ((tmp (gensym))) | |
55 | `(let ((,tmp ,x)) | |
56 | (format t "~&~S: ~S~%" ',x ,tmp) | |
57 | ,tmp))) | |
58 | ||
59 | (defun stringify (str) | |
60 | "Return a string representation of STR. Strings are returned unchanged; | |
61 | symbols are converted to their names (unqualified!). Other objects are | |
62 | converted to their print representations." | |
63 | (typecase str | |
64 | (string str) | |
65 | (symbol (symbol-name str)) | |
66 | (t (with-output-to-string (s) | |
67 | (princ str s))))) | |
02866e07 | 68 | |
861345b4 | 69 | (compile-time-defun listify (x) |
70 | "If X is a (possibly empty) list, return X; otherwise return (list X)." | |
71 | (if (listp x) x (list x))) | |
02866e07 | 72 | |
861345b4 | 73 | (compile-time-defun do-fix-pair (x y defaultp) |
74 | "Helper function for fix-pair and pairify." | |
75 | (flet ((singleton (x) (values x (if defaultp y x)))) | |
76 | (cond ((atom x) (singleton x)) | |
77 | ((null (cdr x)) (singleton (car x))) | |
78 | ((atom (cdr x)) (values (car x) (cdr x))) | |
79 | ((cddr x) (error "Too many elements for a pair.")) | |
80 | (t (values (car x) (cadr x)))))) | |
02866e07 | 81 | |
861345b4 | 82 | (compile-time-defun fix-pair (x &optional (y nil defaultp)) |
83 | "Return two values extracted from X. It works as follows: | |
84 | (A) -> A, Y | |
85 | (A B) -> A, B | |
86 | (A B . C) -> error | |
87 | (A . B) -> A, B | |
88 | A -> A, Y | |
89 | where Y defaults to A if not specified." | |
90 | (do-fix-pair x y defaultp)) | |
02866e07 | 91 | |
861345b4 | 92 | (compile-time-defun pairify (x &optional (y nil defaultp)) |
93 | "As for fix-pair, but returns a list instead of two values." | |
94 | (multiple-value-call #'list (do-fix-pair x y defaultp))) | |
95 | ||
96 | (defun whitespace-char-p (ch) | |
97 | "Return whether CH is a whitespace character or not." | |
98 | (case ch | |
99 | ((#\space #\tab #\newline #\return #\vt #\formfeed) t) | |
100 | (t nil))) | |
101 | ||
102 | (declaim (ftype (function nil ()) slot-unitialized)) | |
103 | (defun slot-uninitialized () | |
104 | "A function which signals an error. Can be used as an initializer form in | |
105 | structure definitions without doom ensuing." | |
106 | (error "No initializer for slot.")) | |
107 | ||
9d3ccec7 MW |
108 | (compile-time-defun parse-body (body) |
109 | "Given a BODY (a list of forms), parses it into three sections: a | |
110 | docstring, a list of declarations (forms beginning with the symbol `declare') | |
111 | and the body forms. The result is returned as three lists (even the | |
112 | docstring), suitable for interpolation into a backquoted list using `@,'." | |
113 | (multiple-value-bind | |
114 | (doc body) | |
115 | (if (and (consp body) | |
116 | (stringp (car body))) | |
117 | (values (list (car body)) (cdr body)) | |
118 | (values nil body)) | |
119 | (loop for forms on body | |
120 | for form = (car forms) | |
121 | while (and (consp form) | |
122 | (eq (car form) 'declare)) | |
123 | collect form into decls | |
124 | finally (return (values doc decls forms))))) | |
125 | ||
02866e07 MW |
126 | ;;;-------------------------------------------------------------------------- |
127 | ;;; Generating symbols. | |
128 | ||
861345b4 | 129 | (defmacro with-gensyms (syms &body body) |
130 | "Everyone's favourite macro helper." | |
131 | `(let (,@(mapcar (lambda (sym) `(,sym (gensym ,(symbol-name sym)))) | |
132 | (listify syms))) | |
133 | ,@body)) | |
134 | ||
135 | (defmacro let*/gensyms (binds &body body) | |
136 | "A macro helper. BINDS is a list of binding pairs (VAR VALUE), where VALUE | |
137 | defaults to VAR. The result is that BODY is evaluated in a context where | |
138 | each VAR is bound to a gensym, and in the final expansion, each of those | |
139 | gensyms will be bound to the corresponding VALUE." | |
140 | (labels ((more (binds) | |
141 | (let ((tmp (gensym "TMP")) (bind (car binds))) | |
142 | `((let ((,tmp ,(cadr bind)) | |
143 | (,(car bind) (gensym ,(symbol-name (car bind))))) | |
144 | `(let ((,,(car bind) ,,tmp)) | |
145 | ,,@(if (cdr binds) | |
146 | (more (cdr binds)) | |
147 | body))))))) | |
148 | (if (null binds) | |
149 | `(progn ,@body) | |
150 | (car (more (mapcar #'pairify (listify binds))))))) | |
151 | ||
02866e07 | 152 | ;;;-------------------------------------------------------------------------- |
f2d46aaa MW |
153 | ;;; Some simple yet useful control structures. |
154 | ||
155 | (defmacro nlet (name binds &body body) | |
156 | "Scheme's named let." | |
157 | (multiple-value-bind (vars vals) | |
158 | (loop for bind in binds | |
159 | for (var val) = (pairify bind nil) | |
160 | collect var into vars | |
161 | collect val into vals | |
162 | finally (return (values vars vals))) | |
163 | `(labels ((,name ,vars | |
164 | ,@body)) | |
165 | (,name ,@vals)))) | |
166 | ||
167 | (defmacro while (cond &body body) | |
168 | "If COND is false, evaluate to nil; otherwise evaluate BODY and try again." | |
169 | `(loop | |
93f04724 | 170 | (unless ,cond (return)) |
f2d46aaa MW |
171 | ,@body)) |
172 | ||
560e1186 MW |
173 | (compile-time-defun do-case2-like (kind vform clauses) |
174 | "Helper function for `case2' and `ecase2'." | |
175 | (with-gensyms (scrutinee argument) | |
176 | `(multiple-value-bind (,scrutinee ,argument) ,vform | |
177 | (declare (ignorable ,argument)) | |
178 | (,kind ,scrutinee | |
179 | ,@(mapcar (lambda (clause) | |
180 | (destructuring-bind | |
181 | (cases (&optional var) &rest forms) | |
182 | clause | |
183 | `(,cases | |
184 | ,@(if var | |
185 | (list `(let ((,var ,argument)) ,@forms)) | |
186 | forms)))) | |
187 | clauses))))) | |
188 | ||
189 | (defmacro case2 (vform &body clauses) | |
190 | "VFORM is a form which evaluates to two values, SCRUTINEE and ARGUMENT. | |
191 | The CLAUSES have the form (CASES ([VAR]) FORMS...), where a standard `case' | |
192 | clause has the form (CASES FORMS...). The `case2' form evaluates the VFORM, | |
193 | and compares the SCRUTINEE to the various CASES, in order, just like `case'. | |
194 | If there is a match, then the corresponding FORMs are evaluated with VAR (if | |
195 | specified) bound to the value of ARGUMENT." | |
196 | (do-case2-like 'case vform clauses)) | |
197 | ||
198 | (defmacro ecase2 (vform &body clauses) | |
199 | "Like `case2', but signals an error if no clause matches the SCRUTINEE." | |
200 | (do-case2-like 'ecase vform clauses)) | |
201 | ||
f2d46aaa | 202 | ;;;-------------------------------------------------------------------------- |
02866e07 MW |
203 | ;;; with-places |
204 | ||
861345b4 | 205 | (defmacro %place-ref (getform setform newtmp) |
206 | "Grim helper macro for with-places." | |
207 | (declare (ignore setform newtmp)) | |
208 | getform) | |
02866e07 | 209 | |
861345b4 | 210 | (define-setf-expander %place-ref (getform setform newtmp) |
211 | "Grim helper macro for with-places." | |
212 | (values nil nil newtmp setform getform)) | |
02866e07 | 213 | |
861345b4 | 214 | (defmacro with-places ((&key environment) places &body body) |
215 | "A hairy helper, for writing setf-like macros. PLACES is a list of binding | |
216 | pairs (VAR PLACE), where PLACE defaults to VAR. The result is that BODY is | |
217 | evaluated in a context where each VAR is bound to a gensym, and in the final | |
218 | expansion, each of those gensyms will be bound to a symbol-macro capable of | |
219 | reading or setting the value of the corresponding PLACE." | |
220 | (if (null places) | |
221 | `(progn ,@body) | |
222 | (let*/gensyms (environment) | |
223 | (labels | |
224 | ((more (places) | |
225 | (let ((place (car places))) | |
226 | (with-gensyms (tmp valtmps valforms | |
227 | newtmps setform getform) | |
228 | `((let ((,tmp ,(cadr place)) | |
229 | (,(car place) | |
230 | (gensym ,(symbol-name (car place))))) | |
231 | (multiple-value-bind | |
232 | (,valtmps ,valforms | |
233 | ,newtmps ,setform ,getform) | |
234 | (get-setf-expansion ,tmp | |
235 | ,environment) | |
236 | (list 'let* | |
237 | (mapcar #'list ,valtmps ,valforms) | |
238 | `(symbol-macrolet ((,,(car place) | |
239 | (%place-ref ,,getform | |
240 | ,,setform | |
241 | ,,newtmps))) | |
242 | ,,@(if (cdr places) | |
243 | (more (cdr places)) | |
244 | body)))))))))) | |
245 | (car (more (mapcar #'pairify (listify places)))))))) | |
246 | ||
02866e07 MW |
247 | ;;;-------------------------------------------------------------------------- |
248 | ;;; Update-in-place macros built using with-places. | |
249 | ||
e979e568 MW |
250 | (defmacro update-place (op place arg &environment env) |
251 | "Update PLACE with the value of OP PLACE ARG, returning the new value." | |
252 | (with-places (:environment env) (place) | |
253 | `(setf ,place (,op ,place ,arg)))) | |
02866e07 | 254 | |
e979e568 MW |
255 | (defmacro update-place-after (op place arg &environment env) |
256 | "Update PLACE with the value of OP PLACE ARG, returning the old value." | |
257 | (with-places (:environment env) (place) | |
258 | (with-gensyms (x) | |
259 | `(let ((,x ,place)) | |
02866e07 MW |
260 | (setf ,place (,op ,x ,arg)) |
261 | ,x)))) | |
262 | ||
e979e568 MW |
263 | (defmacro incf-after (place &optional (by 1)) |
264 | "Increment PLACE by BY, returning the old value." | |
265 | `(update-place-after + ,place ,by)) | |
02866e07 | 266 | |
e979e568 MW |
267 | (defmacro decf-after (place &optional (by 1)) |
268 | "Decrement PLACE by BY, returning the old value." | |
269 | `(update-place-after - ,place ,by)) | |
270 | ||
02866e07 MW |
271 | ;;;-------------------------------------------------------------------------- |
272 | ;;; Locatives. | |
e979e568 | 273 | |
861345b4 | 274 | (defstruct (loc (:predicate locp) (:constructor make-loc (reader writer))) |
275 | "Locative data type. See `locf' and `ref'." | |
276 | (reader (slot-uninitialized) :type function) | |
277 | (writer (slot-uninitialized) :type function)) | |
02866e07 | 278 | |
861345b4 | 279 | (defmacro locf (place &environment env) |
280 | "Slightly cheesy locatives. (locf PLACE) returns an object which, using | |
281 | the `ref' function, can be used to read or set the value of PLACE. It's | |
282 | cheesy because it uses closures rather than actually taking the address of | |
283 | something. Also, unlike Zetalisp, we don't overload `car' to do our dirty | |
284 | work." | |
285 | (multiple-value-bind | |
286 | (valtmps valforms newtmps setform getform) | |
287 | (get-setf-expansion place env) | |
288 | `(let* (,@(mapcar #'list valtmps valforms)) | |
289 | (make-loc (lambda () ,getform) | |
290 | (lambda (,@newtmps) ,setform))))) | |
02866e07 | 291 | |
861345b4 | 292 | (declaim (inline loc (setf loc))) |
02866e07 | 293 | |
861345b4 | 294 | (defun ref (loc) |
295 | "Fetch the value referred to by a locative." | |
296 | (funcall (loc-reader loc))) | |
02866e07 | 297 | |
861345b4 | 298 | (defun (setf ref) (new loc) |
299 | "Store a new value in the place referred to by a locative." | |
300 | (funcall (loc-writer loc) new)) | |
02866e07 | 301 | |
861345b4 | 302 | (defmacro with-locatives (locs &body body) |
303 | "LOCS is a list of items of the form (SYM [LOC-EXPR]), where SYM is a | |
304 | symbol and LOC-EXPR evaluates to a locative. If LOC-EXPR is omitted, it | |
305 | defaults to SYM. As an abbreviation for a common case, LOCS may be a symbol | |
306 | instead of a list. The BODY is evaluated in an environment where each SYM is | |
307 | a symbol macro which expands to (ref LOC-EXPR) -- or, in fact, something | |
308 | similar which doesn't break if LOC-EXPR has side-effects. Thus, references, | |
309 | including `setf' forms, fetch or modify the thing referred to by the | |
310 | LOC-EXPR. Useful for covering over where something uses a locative." | |
311 | (setf locs (mapcar #'pairify (listify locs))) | |
312 | (let ((tt (mapcar (lambda (l) (declare (ignore l)) (gensym)) locs)) | |
313 | (ll (mapcar #'cadr locs)) | |
314 | (ss (mapcar #'car locs))) | |
315 | `(let (,@(mapcar (lambda (tmp loc) `(,tmp ,loc)) tt ll)) | |
316 | (symbol-macrolet (,@(mapcar (lambda (sym tmp) | |
317 | `(,sym (ref ,tmp))) ss tt)) | |
318 | ,@body)))) | |
319 | ||
320 | ;;;----- That's all, folks -------------------------------------------------- |