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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 | |
33 | #:stringify #:listify #:fix-pair #:pairify | |
34 | #:whitespace-char-p | |
35 | #:slot-uninitialized | |
36 | #:with-gensyms #:let*/gensyms #:with-places | |
e979e568 MW |
37 | #:locp #:locf #:ref #:with-locatives |
38 | #:update-place #:update-place-after | |
39 | #:incf-after #:decf-after)) | |
861345b4 | 40 | (in-package #:mdw.base) |
41 | ||
02866e07 MW |
42 | ;;;-------------------------------------------------------------------------- |
43 | ;;; Some simple macros to get things going. | |
44 | ||
861345b4 | 45 | (defmacro compile-time-defun (name args &body body) |
46 | "Define a function which can be used by macros during the compilation | |
47 | process." | |
48 | `(eval-when (:compile-toplevel :load-toplevel) | |
49 | (defun ,name ,args ,@body))) | |
50 | ||
51 | (defmacro show (x) | |
52 | "Debugging tool: print the expression X and its value." | |
53 | (let ((tmp (gensym))) | |
54 | `(let ((,tmp ,x)) | |
55 | (format t "~&~S: ~S~%" ',x ,tmp) | |
56 | ,tmp))) | |
57 | ||
58 | (defun stringify (str) | |
59 | "Return a string representation of STR. Strings are returned unchanged; | |
60 | symbols are converted to their names (unqualified!). Other objects are | |
61 | converted to their print representations." | |
62 | (typecase str | |
63 | (string str) | |
64 | (symbol (symbol-name str)) | |
65 | (t (with-output-to-string (s) | |
66 | (princ str s))))) | |
02866e07 | 67 | |
861345b4 | 68 | (compile-time-defun listify (x) |
69 | "If X is a (possibly empty) list, return X; otherwise return (list X)." | |
70 | (if (listp x) x (list x))) | |
02866e07 | 71 | |
861345b4 | 72 | (compile-time-defun do-fix-pair (x y defaultp) |
73 | "Helper function for fix-pair and pairify." | |
74 | (flet ((singleton (x) (values x (if defaultp y x)))) | |
75 | (cond ((atom x) (singleton x)) | |
76 | ((null (cdr x)) (singleton (car x))) | |
77 | ((atom (cdr x)) (values (car x) (cdr x))) | |
78 | ((cddr x) (error "Too many elements for a pair.")) | |
79 | (t (values (car x) (cadr x)))))) | |
02866e07 | 80 | |
861345b4 | 81 | (compile-time-defun fix-pair (x &optional (y nil defaultp)) |
82 | "Return two values extracted from X. It works as follows: | |
83 | (A) -> A, Y | |
84 | (A B) -> A, B | |
85 | (A B . C) -> error | |
86 | (A . B) -> A, B | |
87 | A -> A, Y | |
88 | where Y defaults to A if not specified." | |
89 | (do-fix-pair x y defaultp)) | |
02866e07 | 90 | |
861345b4 | 91 | (compile-time-defun pairify (x &optional (y nil defaultp)) |
92 | "As for fix-pair, but returns a list instead of two values." | |
93 | (multiple-value-call #'list (do-fix-pair x y defaultp))) | |
94 | ||
95 | (defun whitespace-char-p (ch) | |
96 | "Return whether CH is a whitespace character or not." | |
97 | (case ch | |
98 | ((#\space #\tab #\newline #\return #\vt #\formfeed) t) | |
99 | (t nil))) | |
100 | ||
ec18c92a | 101 | (defmacro nlet (name binds &body body) |
102 | "Scheme's named let." | |
103 | (multiple-value-bind (vars vals) | |
104 | (loop for bind in binds | |
105 | for (var val) = (pairify bind nil) | |
106 | collect var into vars | |
107 | collect val into vals | |
108 | finally (return (values vars vals))) | |
109 | `(labels ((,name ,vars | |
110 | ,@body)) | |
111 | (,name ,@vals)))) | |
112 | ||
113 | (defmacro while (cond &body body) | |
114 | "If COND is false, evaluate to nil; otherwise evaluate BODY and try again." | |
115 | `(loop | |
116 | (unless `cond (return)) | |
117 | ,@body)) | |
118 | ||
861345b4 | 119 | (declaim (ftype (function nil ()) slot-unitialized)) |
120 | (defun slot-uninitialized () | |
121 | "A function which signals an error. Can be used as an initializer form in | |
122 | structure definitions without doom ensuing." | |
123 | (error "No initializer for slot.")) | |
124 | ||
02866e07 MW |
125 | ;;;-------------------------------------------------------------------------- |
126 | ;;; Generating symbols. | |
127 | ||
861345b4 | 128 | (defmacro with-gensyms (syms &body body) |
129 | "Everyone's favourite macro helper." | |
130 | `(let (,@(mapcar (lambda (sym) `(,sym (gensym ,(symbol-name sym)))) | |
131 | (listify syms))) | |
132 | ,@body)) | |
133 | ||
134 | (defmacro let*/gensyms (binds &body body) | |
135 | "A macro helper. BINDS is a list of binding pairs (VAR VALUE), where VALUE | |
136 | defaults to VAR. The result is that BODY is evaluated in a context where | |
137 | each VAR is bound to a gensym, and in the final expansion, each of those | |
138 | gensyms will be bound to the corresponding VALUE." | |
139 | (labels ((more (binds) | |
140 | (let ((tmp (gensym "TMP")) (bind (car binds))) | |
141 | `((let ((,tmp ,(cadr bind)) | |
142 | (,(car bind) (gensym ,(symbol-name (car bind))))) | |
143 | `(let ((,,(car bind) ,,tmp)) | |
144 | ,,@(if (cdr binds) | |
145 | (more (cdr binds)) | |
146 | body))))))) | |
147 | (if (null binds) | |
148 | `(progn ,@body) | |
149 | (car (more (mapcar #'pairify (listify binds))))))) | |
150 | ||
02866e07 MW |
151 | ;;;-------------------------------------------------------------------------- |
152 | ;;; with-places | |
153 | ||
861345b4 | 154 | (defmacro %place-ref (getform setform newtmp) |
155 | "Grim helper macro for with-places." | |
156 | (declare (ignore setform newtmp)) | |
157 | getform) | |
02866e07 | 158 | |
861345b4 | 159 | (define-setf-expander %place-ref (getform setform newtmp) |
160 | "Grim helper macro for with-places." | |
161 | (values nil nil newtmp setform getform)) | |
02866e07 | 162 | |
861345b4 | 163 | (defmacro with-places ((&key environment) places &body body) |
164 | "A hairy helper, for writing setf-like macros. PLACES is a list of binding | |
165 | pairs (VAR PLACE), where PLACE defaults to VAR. The result is that BODY is | |
166 | evaluated in a context where each VAR is bound to a gensym, and in the final | |
167 | expansion, each of those gensyms will be bound to a symbol-macro capable of | |
168 | reading or setting the value of the corresponding PLACE." | |
169 | (if (null places) | |
170 | `(progn ,@body) | |
171 | (let*/gensyms (environment) | |
172 | (labels | |
173 | ((more (places) | |
174 | (let ((place (car places))) | |
175 | (with-gensyms (tmp valtmps valforms | |
176 | newtmps setform getform) | |
177 | `((let ((,tmp ,(cadr place)) | |
178 | (,(car place) | |
179 | (gensym ,(symbol-name (car place))))) | |
180 | (multiple-value-bind | |
181 | (,valtmps ,valforms | |
182 | ,newtmps ,setform ,getform) | |
183 | (get-setf-expansion ,tmp | |
184 | ,environment) | |
185 | (list 'let* | |
186 | (mapcar #'list ,valtmps ,valforms) | |
187 | `(symbol-macrolet ((,,(car place) | |
188 | (%place-ref ,,getform | |
189 | ,,setform | |
190 | ,,newtmps))) | |
191 | ,,@(if (cdr places) | |
192 | (more (cdr places)) | |
193 | body)))))))))) | |
194 | (car (more (mapcar #'pairify (listify places)))))))) | |
195 | ||
02866e07 MW |
196 | ;;;-------------------------------------------------------------------------- |
197 | ;;; Update-in-place macros built using with-places. | |
198 | ||
e979e568 MW |
199 | (defmacro update-place (op place arg &environment env) |
200 | "Update PLACE with the value of OP PLACE ARG, returning the new value." | |
201 | (with-places (:environment env) (place) | |
202 | `(setf ,place (,op ,place ,arg)))) | |
02866e07 | 203 | |
e979e568 MW |
204 | (defmacro update-place-after (op place arg &environment env) |
205 | "Update PLACE with the value of OP PLACE ARG, returning the old value." | |
206 | (with-places (:environment env) (place) | |
207 | (with-gensyms (x) | |
208 | `(let ((,x ,place)) | |
02866e07 MW |
209 | (setf ,place (,op ,x ,arg)) |
210 | ,x)))) | |
211 | ||
e979e568 MW |
212 | (defmacro incf-after (place &optional (by 1)) |
213 | "Increment PLACE by BY, returning the old value." | |
214 | `(update-place-after + ,place ,by)) | |
02866e07 | 215 | |
e979e568 MW |
216 | (defmacro decf-after (place &optional (by 1)) |
217 | "Decrement PLACE by BY, returning the old value." | |
218 | `(update-place-after - ,place ,by)) | |
219 | ||
02866e07 MW |
220 | ;;;-------------------------------------------------------------------------- |
221 | ;;; Locatives. | |
e979e568 | 222 | |
861345b4 | 223 | (defstruct (loc (:predicate locp) (:constructor make-loc (reader writer))) |
224 | "Locative data type. See `locf' and `ref'." | |
225 | (reader (slot-uninitialized) :type function) | |
226 | (writer (slot-uninitialized) :type function)) | |
02866e07 | 227 | |
861345b4 | 228 | (defmacro locf (place &environment env) |
229 | "Slightly cheesy locatives. (locf PLACE) returns an object which, using | |
230 | the `ref' function, can be used to read or set the value of PLACE. It's | |
231 | cheesy because it uses closures rather than actually taking the address of | |
232 | something. Also, unlike Zetalisp, we don't overload `car' to do our dirty | |
233 | work." | |
234 | (multiple-value-bind | |
235 | (valtmps valforms newtmps setform getform) | |
236 | (get-setf-expansion place env) | |
237 | `(let* (,@(mapcar #'list valtmps valforms)) | |
238 | (make-loc (lambda () ,getform) | |
239 | (lambda (,@newtmps) ,setform))))) | |
02866e07 | 240 | |
861345b4 | 241 | (declaim (inline loc (setf loc))) |
02866e07 | 242 | |
861345b4 | 243 | (defun ref (loc) |
244 | "Fetch the value referred to by a locative." | |
245 | (funcall (loc-reader loc))) | |
02866e07 | 246 | |
861345b4 | 247 | (defun (setf ref) (new loc) |
248 | "Store a new value in the place referred to by a locative." | |
249 | (funcall (loc-writer loc) new)) | |
02866e07 | 250 | |
861345b4 | 251 | (defmacro with-locatives (locs &body body) |
252 | "LOCS is a list of items of the form (SYM [LOC-EXPR]), where SYM is a | |
253 | symbol and LOC-EXPR evaluates to a locative. If LOC-EXPR is omitted, it | |
254 | defaults to SYM. As an abbreviation for a common case, LOCS may be a symbol | |
255 | instead of a list. The BODY is evaluated in an environment where each SYM is | |
256 | a symbol macro which expands to (ref LOC-EXPR) -- or, in fact, something | |
257 | similar which doesn't break if LOC-EXPR has side-effects. Thus, references, | |
258 | including `setf' forms, fetch or modify the thing referred to by the | |
259 | LOC-EXPR. Useful for covering over where something uses a locative." | |
260 | (setf locs (mapcar #'pairify (listify locs))) | |
261 | (let ((tt (mapcar (lambda (l) (declare (ignore l)) (gensym)) locs)) | |
262 | (ll (mapcar #'cadr locs)) | |
263 | (ss (mapcar #'car locs))) | |
264 | `(let (,@(mapcar (lambda (tmp loc) `(,tmp ,loc)) tt ll)) | |
265 | (symbol-macrolet (,@(mapcar (lambda (sym tmp) | |
266 | `(,sym (ref ,tmp))) ss tt)) | |
267 | ,@body)))) | |
268 | ||
269 | ;;;----- That's all, folks -------------------------------------------------- |