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1 | ;;; -*-lisp-*- |
2 | ;;; | |
3 | ;;; $Id$ | |
4 | ;;; | |
5 | ;;; Useful bits of MOP hacking | |
6 | ;;; | |
7 | ;;; (c) 2006 Straylight/Edgeware | |
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. | |
b2c12b4e | 16 | ;;; |
e96e008d MW |
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. | |
b2c12b4e | 21 | ;;; |
e96e008d MW |
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 | ||
26 | ;;;-------------------------------------------------------------------------- | |
27 | ;;; Packages. | |
28 | ||
29 | (defpackage #:mdw.mop | |
e5152ebe | 30 | (:use #:common-lisp #:mdw.base #+(or cmu clisp) #:mop #+ecl #:clos) |
20be6570 | 31 | (:export #:copy-instance #:copy-instance-using-class |
5cf4440b | 32 | #:with-slot-variables |
20be6570 | 33 | #:compatible-class |
e96e008d MW |
34 | #:initargs-for-effective-slot #:make-effective-slot |
35 | #:filtered-slot-class-mixin | |
36 | #:filtered-direct-slot-definition | |
37 | #:filtered-effective-slot-definition | |
9b2e67a5 | 38 | #:predicate-class-mixin |
e96e008d | 39 | #:abstract-class-mixin #:instantiate-abstract-class |
46cd5c4b MW |
40 | #:singleton-class-mixin |
41 | #:mdw-class #:abstract-class #:singleton-class | |
e96e008d MW |
42 | #:print-object-with-slots)) |
43 | ||
44 | (in-package #:mdw.mop) | |
45 | ||
20be6570 MW |
46 | ;;;-------------------------------------------------------------------------- |
47 | ;;; Copying instances. | |
48 | ||
49 | (defgeneric copy-instance-using-class (class object &rest initargs) | |
50 | (:documentation | |
51 | "Does the donkey-work behind copy-instance.")) | |
52 | ||
53 | (defmethod copy-instance-using-class | |
54 | ((class standard-class) object &rest initargs) | |
55 | (let ((new (apply #'allocate-instance class initargs))) | |
56 | (dolist (slot (class-slots class)) | |
57 | (setf (slot-value-using-class class new slot) | |
58 | (slot-value-using-class class object slot))) | |
59 | (apply #'shared-initialize new nil initargs) | |
60 | new)) | |
61 | ||
62 | (defun copy-instance (object &rest initargs) | |
63 | "Make a copy of OBJECT, modifying it by setting slots as requested by | |
64 | INITARGS." | |
65 | (apply #'copy-instance-using-class (class-of object) object initargs)) | |
66 | ||
5cf4440b MW |
67 | ;;;-------------------------------------------------------------------------- |
68 | ;;; Handy macros. | |
69 | ||
70 | (defmacro with-slot-variables (slots instance &body body) | |
71 | "A copy-out-and-write-back variant of with-slots. | |
72 | ||
73 | The SLOTS argument is a list of slot specifications, each of which has the | |
74 | form (NAME &key :update :variable). VARIABLE defaults to NAME, and | |
75 | :update defaults to nil. | |
76 | ||
77 | The INSTANCE argument has the form (INSTANCE &key :class), but an atom may | |
78 | be used in place of a singleton list. If the CLASS is specified, then two | |
79 | good things happen: firstly the INSTANCE is declared to be a member of the | |
80 | CLASS, and secondly all the slot variables are declared to have the | |
81 | appropriate types, as dredged up from the class's effective slot | |
82 | definitions. | |
83 | ||
84 | The effect of all this is to return the result of evaluating BODY in an | |
85 | environment where the VARIABLEs are bound to the values of the NAMEd slots | |
86 | of the given INSTANCE. If BODY completes successfully (rather than | |
87 | throwing out, restarting, or anything like that) then the final values of | |
88 | VARIABLEs for which UPDATE was set non-nil are written back to their | |
89 | corresponding slots. | |
90 | ||
91 | This stands a good chance of being rather faster than with-slots. It | |
92 | does, however, run the risk of leaving things in an inconsistent state if | |
93 | BODY escapes half-way through. Also, this requires recompilation if a | |
94 | class's slots change type." | |
95 | (multiple-value-bind (instance class) | |
96 | (destructuring-bind | |
97 | (instance &key class) | |
98 | (listify instance) | |
99 | (values instance (and class (find-class class)))) | |
100 | (let ((slots (mapcar (lambda (slot) | |
101 | (destructuring-bind | |
102 | (name &key update (variable name)) | |
103 | (listify slot) | |
104 | (list name variable update))) | |
105 | (if slots | |
106 | (listify slots) | |
107 | (mapcar #'slot-definition-name | |
108 | (class-slots class)))))) | |
8f801ae8 | 109 | (with-parsed-body (body decls) body |
5cf4440b MW |
110 | (with-gensyms (instvar) |
111 | `(let ((,instvar ,instance)) | |
112 | ,@(and class `((declare (type ,(class-name class) ,instvar)))) | |
113 | (let ,(loop for (name var update) in slots | |
114 | collect `(,var (slot-value ,instvar ',name))) | |
115 | ,@(and class | |
116 | `((declare | |
117 | ,@(loop | |
118 | for (name var update) in slots | |
119 | for slot = (or (find name | |
120 | (class-slots class) | |
121 | :key #'slot-definition-name) | |
122 | (error | |
123 | "Slot ~S not found in class ~S." | |
124 | name (class-name class))) | |
125 | collect `(type | |
126 | ,(slot-definition-type slot) | |
127 | ,name))))) | |
128 | ,@decls | |
129 | (multiple-value-prog1 | |
130 | (progn ,@body) | |
131 | ,@(loop for (name var update) in slots | |
132 | when update | |
133 | collect `(setf (slot-value ,instvar ',name) | |
134 | ,var)))))))))) | |
135 | ||
e96e008d MW |
136 | ;;;-------------------------------------------------------------------------- |
137 | ;;; Basic stuff. | |
138 | ||
139 | (defclass compatible-class (standard-class) | |
140 | () | |
141 | (:documentation | |
142 | "A class which can be be freely used in class heirarchies with | |
143 | standard-class and other subclasses of compatible-class. This saves a | |
144 | bunch of annoying messing about with `validate-superclass'.")) | |
145 | ||
146 | (defmethod validate-superclass | |
147 | ((sub compatible-class) (super compatible-class)) | |
148 | t) | |
149 | ||
150 | (defmethod validate-superclass | |
151 | ((sub compatible-class) (super standard-class)) | |
152 | (eq (class-of super) (find-class 'standard-class))) | |
153 | ||
154 | (defmethod validate-superclass | |
155 | ((sub standard-class) (super compatible-class)) | |
156 | (eq (class-of sub) (find-class 'standard-class))) | |
157 | ||
158 | ;;;-------------------------------------------------------------------------- | |
159 | ;;; Utilities for messing with slot options. | |
160 | ||
161 | (defgeneric initargs-for-effective-slot (class direct-slots) | |
162 | (:documentation | |
163 | "Missing functionality from the MOP: given a class and its direct slots | |
164 | definitions, construct and return the proposed initializer list for | |
165 | constructing the effective-slot.")) | |
166 | ||
167 | (defmethod initargs-for-effective-slot | |
168 | ((class standard-class) direct-slots) | |
169 | "Extract the effective slot options as required." | |
170 | ;; | |
171 | ;; This is taken from the Closette implementation, but it seems to work! | |
172 | (let ((init-slot (find-if-not #'null direct-slots | |
173 | :key #'slot-definition-initfunction))) | |
174 | (list :name (slot-definition-name (car direct-slots)) | |
175 | :initform (and init-slot | |
176 | (slot-definition-initform init-slot)) | |
177 | :initfunction (and init-slot | |
178 | (slot-definition-initfunction init-slot)) | |
179 | :initargs (remove-duplicates | |
180 | (apply #'append | |
181 | (mapcar #'slot-definition-initargs | |
182 | direct-slots))) | |
183 | :allocation (slot-definition-allocation (car direct-slots))))) | |
184 | ||
185 | (defun make-effective-slot (class initargs) | |
186 | "Construct an effectie slot definition for a slot on the class, given the | |
187 | required arguments." | |
188 | (apply #'make-instance | |
189 | (apply #'effective-slot-definition-class class initargs) | |
190 | initargs)) | |
191 | ||
192 | (let ((stdslot (find-class 'standard-direct-slot-definition))) | |
193 | (defmethod compute-effective-slot-definition | |
194 | ((class compatible-class) slot-name direct-slots) | |
195 | "Construct an effective slot definition for the given slot." | |
8a2e8de1 | 196 | (declare (ignore slot-name)) |
e96e008d MW |
197 | ;; |
198 | ;; Ideally we don't want to mess with a slot if it's entirely handled by | |
199 | ;; the implementation. This check seems to work OK. | |
200 | (if (every (lambda (slot) | |
201 | (member (class-of slot) | |
202 | (class-precedence-list stdslot))) | |
203 | direct-slots) | |
204 | (call-next-method) | |
205 | (make-effective-slot class | |
206 | (initargs-for-effective-slot class | |
207 | direct-slots))))) | |
208 | ||
209 | ;;;-------------------------------------------------------------------------- | |
210 | ;;; Filterered slots. | |
211 | ||
212 | (defclass filtered-slot-class-mixin (compatible-class) | |
213 | () | |
214 | (:documentation | |
215 | "A filtered slot interposes a filter on any attempt to write to the slot. | |
216 | The filter is given the proposed new value, and should return the actual | |
217 | new value. Specify the filter with a `:filter SYMBOL' slot option. | |
218 | (Yes, I know that using functions would be nicer, but the MOP makes | |
219 | that surprisingly difficult.)")) | |
220 | ||
221 | (defclass filtered-direct-slot-definition | |
222 | (standard-direct-slot-definition) | |
223 | ((filter :initarg :filter :reader slot-definition-filter))) | |
224 | ||
225 | (defgeneric slot-definition-filter (slot) | |
226 | (:method ((slot slot-definition)) nil)) | |
227 | ||
228 | (defclass filtered-effective-slot-definition | |
229 | (standard-effective-slot-definition) | |
230 | ((filter :initarg :filter :accessor slot-definition-filter))) | |
231 | ||
232 | (defmethod direct-slot-definition-class | |
233 | ((class filtered-slot-class-mixin) | |
234 | &key (filter nil filterp) &allow-other-keys) | |
235 | (declare (ignore filter)) | |
236 | (if filterp | |
237 | (find-class 'filtered-direct-slot-definition) | |
238 | (call-next-method))) | |
239 | ||
240 | (defmethod effective-slot-definition-class | |
241 | ((class filtered-slot-class-mixin) | |
242 | &key (filter nil filterp) &allow-other-keys) | |
243 | (declare (ignore filter)) | |
244 | (if filterp | |
245 | (find-class 'filtered-effective-slot-definition) | |
246 | (call-next-method))) | |
247 | ||
248 | (defmethod initialize-instance :after | |
920d2b95 | 249 | ((slot filtered-direct-slot-definition) &key) |
e96e008d MW |
250 | (with-slots (filter) slot |
251 | (when (and (consp filter) | |
252 | (or (eq (car filter) 'function) | |
253 | (eq (car filter) 'quote)) | |
254 | (symbolp (cadr filter)) | |
255 | (null (cddr filter))) | |
256 | (setf filter (cadr filter))))) | |
257 | ||
258 | (defmethod initargs-for-effective-slot | |
259 | ((class filtered-slot-class-mixin) direct-slots) | |
260 | (let ((filter-slot (find-if #'slot-definition-filter direct-slots))) | |
261 | (append (and filter-slot | |
262 | (list :filter (slot-definition-filter filter-slot))) | |
263 | (call-next-method)))) | |
264 | ||
265 | (defmethod (setf slot-value-using-class) | |
266 | (value | |
267 | (class filtered-slot-class-mixin) | |
268 | (object standard-object) | |
269 | (slot filtered-effective-slot-definition)) | |
25760fe1 | 270 | (call-next-method (funcall (slot-definition-filter slot) value) |
e96e008d MW |
271 | class object slot)) |
272 | ||
9b2e67a5 MW |
273 | ;;;-------------------------------------------------------------------------- |
274 | ;;; Predicates. | |
275 | ||
276 | (defclass predicate-class-mixin (compatible-class) | |
277 | ((predicates :type list :initarg :predicate :initform nil | |
278 | :documentation "Predicate generic function to create.")) | |
279 | (:documentation | |
280 | "Class which can automatically generate a predicate generic function. | |
281 | Adds the `:predicate' class option, which takes a single symbol argument | |
282 | FUNC. If specified, and non-nil, a generic function FUNC with one | |
283 | argument will be defined (if it doesn't already exist) with a default | |
284 | method returning nil, and a method added specialized on this class | |
285 | returning a non-nil value.")) | |
286 | ||
287 | (defmethod shared-initialize :after | |
920d2b95 | 288 | ((class predicate-class-mixin) slot-names &key) |
9b2e67a5 MW |
289 | (declare (ignore slot-names)) |
290 | (with-slots (predicates) class | |
291 | (dolist (predicate predicates) | |
292 | (let ((lambda-list '(thing))) | |
293 | (let ((gf (if (fboundp predicate) | |
294 | (fdefinition predicate) | |
295 | (let ((gf (ensure-generic-function | |
296 | predicate :lambda-list lambda-list))) | |
297 | (add-method gf (make-instance | |
298 | 'standard-method | |
299 | :specializers (list (find-class 't)) | |
300 | :lambda-list lambda-list | |
301 | :function (constantly nil))))))) | |
302 | (add-method gf (make-instance 'standard-method | |
303 | :specializers (list class) | |
304 | :lambda-list lambda-list | |
305 | :function (constantly t)))))))) | |
306 | ||
e96e008d MW |
307 | ;;;-------------------------------------------------------------------------- |
308 | ;;; Abstract classes. | |
309 | ||
310 | (defclass abstract-class-mixin (compatible-class) | |
311 | () | |
312 | (:documentation | |
313 | "Confusingly enough, a concrete metaclass for abstract classes. This | |
314 | class has a `make-instance' implementation which signals an error.")) | |
315 | ||
316 | (define-condition instantiate-abstract-class (error) | |
317 | ((class :reader instantiate-abstract-class-class :initarg :class | |
318 | :documentation "The class someone attempted to instantiate.")) | |
319 | (:report (lambda (cond stream) | |
320 | (format stream "Cannot instantiate abstract class ~A." | |
321 | (class-name (instantiate-abstract-class-class cond))))) | |
322 | (:documentation | |
323 | "Reports an attempt to instantiate an abstract class.")) | |
324 | ||
325 | (defmethod make-instance ((class abstract-class-mixin) &rest whatever) | |
326 | "Signals an error. The caller is a naughty boy." | |
327 | (declare (ignore whatever)) | |
328 | (error 'instantiate-abstract-class :class class)) | |
329 | ||
46cd5c4b MW |
330 | ;;;-------------------------------------------------------------------------- |
331 | ;;; Singleton classes. | |
332 | ||
333 | (defclass singleton-class-mixin (compatible-class) | |
334 | ((instance :initform nil :type (or null standard-object))) | |
335 | (:documentation | |
336 | "A class which has only one instance. All calls to `make-instance' return | |
337 | the same object.")) | |
338 | ||
339 | (defmethod allocate-instance ((class singleton-class-mixin) &key) | |
340 | "If the class already has an instance, return it; otherwise allocate one, | |
341 | store it away, and return that." | |
342 | (with-slots (instance) class | |
343 | (or instance | |
344 | (setf instance (call-next-method))))) | |
345 | ||
e96e008d MW |
346 | ;;;-------------------------------------------------------------------------- |
347 | ;;; Useful classes. | |
348 | ||
349 | (defclass mdw-class (filtered-slot-class-mixin | |
9b2e67a5 | 350 | predicate-class-mixin |
e96e008d | 351 | compatible-class) |
9b2e67a5 MW |
352 | () |
353 | (:documentation | |
354 | "A generally useful metaclass with handy features. If I've done the | |
355 | hacking right, there shouldn't be a significant cost to using this | |
356 | metaclass for all your classes if you don't use any of its fancy | |
357 | features.")) | |
e96e008d MW |
358 | |
359 | (defclass abstract-class (mdw-class abstract-class-mixin) ()) | |
46cd5c4b | 360 | (defclass singleton-class (mdw-class singleton-class-mixin) ()) |
e96e008d MW |
361 | |
362 | ;;;-------------------------------------------------------------------------- | |
363 | ;;; Printing things. | |
364 | ||
365 | (defun print-object-with-slots (obj stream) | |
366 | "Prints objects in a pleasant way. Not too clever about circularity." | |
8a2e8de1 | 367 | (let ((class (class-of obj)) |
e96e008d MW |
368 | (magic (cons 'magic nil))) |
369 | (print-unreadable-object (obj stream) | |
370 | (pprint-logical-block | |
371 | (stream | |
372 | (mapcan (lambda (slot) | |
373 | (list (or (car (slot-definition-initargs slot)) | |
374 | (slot-definition-name slot)) | |
375 | (if (slot-boundp-using-class class obj slot) | |
376 | (slot-value-using-class class obj slot) | |
377 | magic))) | |
8a2e8de1 MW |
378 | (class-slots class))) |
379 | (format stream "~S" (class-name class)) | |
e96e008d MW |
380 | (let ((sep nil)) |
381 | (loop | |
382 | (pprint-exit-if-list-exhausted) | |
383 | (if sep | |
384 | (format stream " ~_") | |
385 | (progn (format stream " ~@_~:I") (setf sep t))) | |
386 | (let ((name (pprint-pop)) | |
387 | (value (pprint-pop))) | |
f4df6cf4 | 388 | (format stream "~S ~@_~:[~W~;#<unbound>~*~]" |
e96e008d MW |
389 | name (eq value magic) value)))))))) |
390 | ||
391 | ;;;----- That's all, folks -------------------------------------------------- |