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1 | ;;; -*-lisp-*- |
2 | ;;; | |
dea4d055 | 3 | ;;; Class finalization implementation |
abdf50aa MW |
4 | ;;; |
5 | ;;; (c) 2009 Straylight/Edgeware | |
6 | ;;; | |
7 | ||
8 | ;;;----- Licensing notice --------------------------------------------------- | |
9 | ;;; | |
e0808c47 | 10 | ;;; This file is part of the Sensible Object Design, an object system for C. |
abdf50aa MW |
11 | ;;; |
12 | ;;; SOD 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 | ;;; SOD 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 SOD; if not, write to the Free Software Foundation, | |
24 | ;;; Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. | |
25 | ||
26 | (cl:in-package #:sod) | |
27 | ||
28 | ;;;-------------------------------------------------------------------------- | |
dea4d055 | 29 | ;;; Class precedence lists. |
abdf50aa | 30 | |
dea4d055 MW |
31 | ;; Just for fun, we implement a wide selection of precedence list algorithms. |
32 | ;; C3 seems to be clearly the best, with fewer sharp edges for the unwary. | |
abdf50aa MW |
33 | ;; |
34 | ;; The extended precedence graph (EPG) is constructed by adding edges to the | |
35 | ;; superclass graph. If A and B are classes, then write A < B if A is a | |
36 | ;; (maybe indirect) subclass of B. For every two classes A and B, and for | |
37 | ;; every /maximal/ subclass of both A and B (i.e., every C for which C < A | |
38 | ;; and C < B, but there does not exist D such that D < A, D < B and C < D): | |
39 | ;; if A precedes B in C's direct superclass list, then draw an edge A -> B, | |
40 | ;; otherwise draw the edge B -> A. | |
41 | ;; | |
42 | ;; A linearization respects the EPG if, whenever A precedes B in the | |
43 | ;; linearization, there is a path from A to B. The EPG can be cyclic; in | |
44 | ;; that case, we don't care which order the classes in the cycle are | |
45 | ;; linearized. | |
46 | ;; | |
47 | ;; See Barrett, Cassels, Haahr, Moon, Playford, Withington, `A Monotonic | |
48 | ;; Superclass Linearization for Dylan' for more detail. | |
49 | ;; http://www.webcom.com/haahr/dylan/linearization-oopsla96.html | |
50 | ||
e2838dc5 MW |
51 | ;;; Utilities. |
52 | ||
53 | (export 'merge-class-lists) | |
54 | (defun merge-class-lists (lists pick) | |
55 | "Merge the LISTS of classes, using PICK to break ties. | |
56 | ||
57 | This is a convenience wrapper around the main `merge-lists' function. | |
58 | Given that class linearizations (almost?) always specify a custom | |
59 | tiebreaker function, this isn't a keyword argument. Also, this wrapper | |
60 | provides a standard presentation function so that any errors are presented | |
61 | properly." | |
62 | (merge-lists lists | |
63 | :pick pick | |
64 | :present (lambda (class) | |
65 | (format nil "`~A'" (sod-class-name class))))) | |
66 | ||
dea4d055 MW |
67 | ;;; Tiebreaker functions. |
68 | ||
abdf50aa MW |
69 | (defun clos-tiebreaker (candidates so-far) |
70 | "The CLOS linearization tiebreaker function. | |
71 | ||
bf090e02 MW |
72 | Intended for use with `merge-lists'. Returns the member of CANDIDATES |
73 | which has a direct subclass furthest to the right in the list SO-FAR. | |
abdf50aa MW |
74 | |
75 | This must disambiguate. The SO-FAR list cannot be empty, since the class | |
76 | under construction precedes all of the others. If two classes share a | |
77 | direct subclass then that subclass's direct superclasses list must order | |
78 | them relative to each other." | |
79 | ||
80 | (let (winner) | |
81 | (dolist (class so-far) | |
82 | (dolist (candidate candidates) | |
83 | (when (member candidate (sod-class-direct-superclasses class)) | |
84 | (setf winner candidate)))) | |
85 | (unless winner | |
a1985b3c | 86 | (error "SOD INTERNAL ERROR: Failed to break tie in CLOS")) |
abdf50aa MW |
87 | winner)) |
88 | ||
dea4d055 MW |
89 | (defun c3-tiebreaker (candidates cpls) |
90 | "The C3 linearization tiebreaker function. | |
91 | ||
bf090e02 MW |
92 | Intended for use with `merge-lists'. Returns the member of CANDIDATES |
93 | which appears in the earliest element of CPLS, which should be the list of | |
94 | the class precedence lists of the direct superclasses of the class in | |
dea4d055 MW |
95 | question, in the order specified in the class declaration. |
96 | ||
97 | The only class in the class precedence list which does not appear in one | |
98 | of these lists is the new class itself, which must precede all of the | |
99 | others. | |
100 | ||
101 | This must disambiguate, since if two classes are in the same class | |
102 | precedence list, then one must appear in it before the other, which | |
103 | provides an ordering between them. (In this situation we return the one | |
104 | that matches earliest anyway, which would still give the right answer.) | |
105 | ||
106 | Note that this will merge the CPLs of superclasses /as they are/, not | |
107 | necessarily as C3 would have computed them. This ensures monotonicity | |
108 | assuming that the superclass CPLs are already monotonic. If they aren't, | |
109 | you're going to lose anyway." | |
110 | ||
111 | (dolist (cpl cpls) | |
112 | (dolist (candidate candidates) | |
113 | (when (member candidate cpl) | |
114 | (return-from c3-tiebreaker candidate)))) | |
a1985b3c | 115 | (error "SOD INTERNAL ERROR: Failed to break tie in C3")) |
dea4d055 MW |
116 | |
117 | ;;; Linearization functions. | |
118 | ||
11e41ddf | 119 | (export 'clos-cpl) |
abdf50aa MW |
120 | (defun clos-cpl (class) |
121 | "Compute the class precedence list of CLASS using CLOS linearization rules. | |
122 | ||
123 | We merge the direct-superclass lists of all of CLASS's superclasses, | |
bf090e02 | 124 | disambiguating using `clos-tiebreaker'. |
abdf50aa MW |
125 | |
126 | The CLOS linearization preserves local class ordering, but is not | |
127 | monotonic, and does not respect the extended precedence graph. CLOS | |
128 | linearization will succeed whenever Dylan or C3 linearization succeeds; | |
129 | the converse is not true." | |
130 | ||
131 | (labels ((superclasses (class) | |
132 | (let ((direct-supers (sod-class-direct-superclasses class))) | |
133 | (remove-duplicates (cons class | |
1f1d88f5 MW |
134 | (mappend #'superclasses |
135 | direct-supers)))))) | |
e2838dc5 MW |
136 | (merge-class-lists |
137 | (mapcar (lambda (class) | |
138 | (cons class (sod-class-direct-superclasses class))) | |
139 | (superclasses class)) | |
140 | #'clos-tiebreaker))) | |
abdf50aa | 141 | |
11e41ddf | 142 | (export 'dylan-cpl) |
abdf50aa MW |
143 | (defun dylan-cpl (class) |
144 | "Compute the class precedence list of CLASS using Dylan linearization | |
145 | rules. | |
146 | ||
147 | We merge the direct-superclass list of CLASS with the full class | |
148 | precedence lists of its direct superclasses, disambiguating using | |
bf090e02 | 149 | `clos-tiebreaker'. (Inductively, these lists will be consistent with the |
abdf50aa MW |
150 | CPLs of indirect superclasses, since those CPLs' orderings are reflected |
151 | in the CPLs of the direct superclasses.) | |
152 | ||
153 | The Dylan linearization preserves local class ordering and is monotonic, | |
154 | but does not respect the extended precedence graph. | |
155 | ||
156 | Note that this will merge the CPLs of superclasses /as they are/, not | |
157 | necessarily as Dylan would have computed them. This ensures monotonicity | |
158 | assuming that the superclass CPLs are already monotonic. If they aren't, | |
159 | you're going to lose anyway." | |
160 | ||
161 | (let ((direct-supers (sod-class-direct-superclasses class))) | |
e2838dc5 MW |
162 | (merge-class-lists |
163 | (cons (cons class direct-supers) | |
164 | (mapcar #'sod-class-precedence-list direct-supers)) | |
165 | #'clos-tiebreaker))) | |
abdf50aa | 166 | |
11e41ddf | 167 | (export 'c3-cpl) |
abdf50aa MW |
168 | (defun c3-cpl (class) |
169 | "Compute the class precedence list of CLASS using C3 linearization rules. | |
170 | ||
171 | We merge the direct-superclass list of CLASS with the full class | |
172 | precedence lists of its direct superclasses, disambiguating using | |
bf090e02 | 173 | `c3-tiebreaker'. |
abdf50aa MW |
174 | |
175 | The C3 linearization preserves local class ordering, is monotonic, and | |
176 | respects the extended precedence graph. It is the linearization used in | |
177 | Python, Perl 6 and other languages. It is the recommended linearization | |
178 | for SOD." | |
179 | ||
180 | (let* ((direct-supers (sod-class-direct-superclasses class)) | |
181 | (cpls (mapcar #'sod-class-precedence-list direct-supers))) | |
e2838dc5 MW |
182 | (merge-class-lists (cons (cons class direct-supers) cpls) |
183 | (lambda (candidates so-far) | |
abdf50aa MW |
184 | (declare (ignore so-far)) |
185 | (c3-tiebreaker candidates cpls))))) | |
186 | ||
11e41ddf | 187 | (export 'flavors-cpl) |
abdf50aa MW |
188 | (defun flavors-cpl (class) |
189 | "Compute the class precedence list of CLASS using Flavors linearization | |
190 | rules. | |
191 | ||
192 | We do a depth-first traversal of the superclass graph, ignoring duplicates | |
193 | of classes we've already visited. Interestingly, this has the property of | |
194 | being able to tolerate cyclic superclass graphs, though defining cyclic | |
195 | graphs is syntactically impossible in SOD. | |
196 | ||
197 | This linearization has few other redeeming features, however. In | |
198 | particular, the top class tends not to be at the end of the CPL, despite | |
199 | it being unequivocally less specific than any other class." | |
200 | ||
201 | (let ((done nil)) | |
202 | (labels ((walk (class) | |
203 | (unless (member class done) | |
204 | (push class done) | |
205 | (dolist (super (sod-class-direct-superclasses class)) | |
206 | (walk super))))) | |
207 | (walk class) | |
208 | (nreverse done)))) | |
209 | ||
11e41ddf | 210 | (export 'python-cpl) |
abdf50aa MW |
211 | (defun python-cpl (class) |
212 | "Compute the class precedence list of CLASS using the documented Python 2.2 | |
213 | linearization rules. | |
214 | ||
215 | We do a depth-first traversal of the superclass graph, retaining only the | |
216 | last occurrence of each class visited. | |
217 | ||
218 | This linearization has few redeeming features. It was never actually | |
219 | implemented; the true Python 2.2 linearization seems closer to (but | |
220 | different from) L*LOOPS." | |
221 | ||
222 | (let ((done nil)) | |
223 | (labels ((walk (class) | |
224 | (push class done) | |
225 | (dolist (super (sod-class-direct-superclasses class)) | |
226 | (walk super)))) | |
227 | (walk class) | |
228 | (delete-duplicates (nreverse done))))) | |
229 | ||
11e41ddf | 230 | (export 'l*loops-cpl) |
abdf50aa MW |
231 | (defun l*loops-cpl (class) |
232 | "Compute the class precedence list of CLASS using L*LOOPS linearization | |
233 | rules. | |
234 | ||
235 | We merge the class precedence lists of the direct superclasses of CLASS, | |
236 | disambiguating by choosing the earliest candidate which appears in a | |
237 | depth-first walk of the superclass graph. | |
238 | ||
239 | The L*LOOPS rules are monotonic and respect the extended precedence | |
240 | graph. However (unlike Dylan and CLOS) they don't respect local | |
241 | precedence order i.e., the direct-superclasses list orderings." | |
242 | ||
243 | (let ((dfs (flavors-cpl class))) | |
e2838dc5 MW |
244 | (cons class |
245 | (merge-class-lists (mapcar #'sod-class-precedence-list | |
abdf50aa | 246 | (sod-class-direct-superclasses class)) |
e2838dc5 MW |
247 | (lambda (candidates so-far) |
248 | (declare (ignore so-far)) | |
249 | (dolist (class dfs) | |
250 | (when (member class candidates) | |
251 | (return class)))))))) | |
abdf50aa | 252 | |
dea4d055 | 253 | ;;; Default function. |
abdf50aa MW |
254 | |
255 | (defmethod compute-cpl ((class sod-class)) | |
256 | (handler-case (c3-cpl class) | |
257 | (inconsistent-merge-error () | |
258 | (error "Failed to compute class precedence list for `~A'" | |
259 | (sod-class-name class))))) | |
260 | ||
261 | ;;;-------------------------------------------------------------------------- | |
dea4d055 MW |
262 | ;;; Chains. |
263 | ||
264 | (defmethod compute-chains ((class sod-class)) | |
265 | (with-default-error-location (class) | |
266 | (with-slots (chain-link class-precedence-list) class | |
267 | (let* ((head (if chain-link | |
268 | (sod-class-chain-head chain-link) | |
269 | class)) | |
270 | (chain (cons class (and chain-link | |
271 | (sod-class-chain chain-link)))) | |
272 | (table (make-hash-table))) | |
273 | ||
274 | ;; Check the chains. We work through each superclass, maintaining a | |
275 | ;; hash table keyed by class. If we encounter a class C which links | |
276 | ;; to L, then we store C as L's value; if L already has a value then | |
277 | ;; we've found an error. By the end of all of this, the classes | |
278 | ;; which don't have an entry are the chain tails. | |
279 | (dolist (super class-precedence-list) | |
280 | (let ((link (sod-class-chain-link super))) | |
281 | (when link | |
282 | (when (gethash link table) | |
283 | (error "Conflicting chains in class ~A: ~ | |
284 | (~A and ~A both link to ~A)" | |
285 | class super (gethash link table) link)) | |
286 | (setf (gethash link table) super)))) | |
287 | ||
288 | ;; Done. | |
289 | (values head chain | |
290 | (cons chain | |
291 | (mapcar #'sod-class-chain | |
292 | (remove-if (lambda (super) | |
293 | (gethash super table)) | |
294 | (cdr class-precedence-list))))))))) | |
295 | ||
981b6fb6 MW |
296 | ;;;-------------------------------------------------------------------------- |
297 | ;;; Metaclasses. | |
298 | ||
981b6fb6 MW |
299 | (defmethod guess-metaclass ((class sod-class)) |
300 | "Default metaclass-guessing function for classes. | |
301 | ||
302 | Return the most specific metaclass of any of the CLASS's direct | |
303 | superclasses." | |
304 | ||
305 | ;; During bootstrapping, our superclasses might not have their own | |
306 | ;; metaclasses resolved yet. If we find this, then throw `bootstrapping' | |
307 | ;; so that `shared-initialize' on `sod-class' can catch it (or as a shot | |
308 | ;; across the bows of anyone else who calls us). | |
6e92afa7 MW |
309 | (select-minimal-class-property (sod-class-direct-superclasses class) |
310 | (lambda (super) | |
311 | (if (slot-boundp super 'metaclass) | |
312 | (slot-value super 'metaclass) | |
313 | (throw 'bootstrapping nil))) | |
314 | #'sod-subclass-p class "metaclass")) | |
981b6fb6 | 315 | |
dea4d055 MW |
316 | ;;;-------------------------------------------------------------------------- |
317 | ;;; Sanity checking. | |
318 | ||
319 | (defmethod check-sod-class ((class sod-class)) | |
320 | (with-default-error-location (class) | |
321 | ||
322 | ;; Check the names of things are valid. | |
323 | (with-slots (name nickname messages) class | |
324 | (unless (valid-name-p name) | |
325 | (error "Invalid class name `~A'" class)) | |
326 | (unless (valid-name-p nickname) | |
327 | (error "Invalid class nickname `~A' on class `~A'" nickname class)) | |
328 | (dolist (message messages) | |
329 | (unless (valid-name-p (sod-message-name message)) | |
330 | (error "Invalid message name `~A' on class `~A'" | |
331 | (sod-message-name message) class)))) | |
332 | ||
333 | ;; Check that the slots and messages have distinct names. | |
334 | (with-slots (slots messages class-precedence-list) class | |
335 | (flet ((check-list (list what namefunc) | |
336 | (let ((table (make-hash-table :test #'equal))) | |
337 | (dolist (item list) | |
338 | (let ((name (funcall namefunc item))) | |
339 | (if (gethash name table) | |
340 | (error "Duplicate ~A name `~A' on class `~A'" | |
341 | what name class) | |
342 | (setf (gethash name table) item))))))) | |
343 | (check-list slots "slot" #'sod-slot-name) | |
344 | (check-list messages "message" #'sod-message-name) | |
345 | (check-list class-precedence-list "nickname" #'sod-class-name))) | |
346 | ||
347 | ;; Check that the CHAIN-TO class is actually a proper superclass. (This | |
348 | ;; eliminates hairy things like a class being its own link.) | |
349 | (with-slots (class-precedence-list chain-link) class | |
350 | (unless (or (not chain-link) | |
351 | (member chain-link (cdr class-precedence-list))) | |
352 | (error "In `~A~, chain-to class `~A' is not a proper superclass" | |
353 | class chain-link))) | |
354 | ||
b2983f35 MW |
355 | ;; Check that the initargs declare compatible types. Duplicate entries, |
356 | ;; even within a class, are harmless, but at most one initarg in any | |
357 | ;; class should declare a default value. | |
358 | (with-slots (class-precedence-list) class | |
359 | (let ((seen (make-hash-table :test #'equal))) | |
360 | (dolist (super class-precedence-list) | |
361 | (with-slots (initargs) super | |
362 | (dolist (initarg (reverse initargs)) | |
363 | (let* ((initarg-name (sod-initarg-name initarg)) | |
364 | (initarg-type (sod-initarg-type initarg)) | |
365 | (initarg-default (sod-initarg-default initarg)) | |
366 | (found (gethash initarg-name seen)) | |
367 | (found-type (and found (sod-initarg-type found))) | |
368 | (found-default (and found (sod-initarg-default found))) | |
369 | (found-class (and found (sod-initarg-class found))) | |
370 | (found-location (and found (file-location found)))) | |
371 | (with-default-error-location (initarg) | |
372 | (cond ((not found) | |
373 | (setf (gethash initarg-name seen) initarg)) | |
374 | ((not (c-type-equal-p initarg-type found-type)) | |
375 | (cerror* "Inititalization argument `~A' defined ~ | |
376 | with incompatible types: ~ | |
377 | ~A in class ~A, and ~ | |
378 | ~A in class ~A (at ~A)" | |
379 | initarg-name initarg-type super | |
380 | found-type found-class found-location)) | |
381 | ((and initarg-default found-default | |
382 | (eql super found-class)) | |
383 | (cerror* "Initialization argument `~A' redefined ~ | |
384 | with default value ~ | |
385 | (previous definition at ~A)" | |
386 | initarg-name found-location)) | |
387 | (initarg-default | |
388 | (setf (gethash initarg-name seen) initarg)))))))))) | |
389 | ||
dea4d055 MW |
390 | ;; Check for circularity in the superclass graph. Since the superclasses |
391 | ;; should already be acyclic, it suffices to check that our class is not | |
392 | ;; a superclass of any of its own direct superclasses. | |
393 | (let ((circle (find-if (lambda (super) | |
394 | (sod-subclass-p super class)) | |
395 | (sod-class-direct-superclasses class)))) | |
396 | (when circle | |
397 | (error "Circularity: ~A is already a superclass of ~A" | |
398 | class circle))) | |
399 | ||
400 | ;; Check that the class has a unique root superclass. | |
401 | (find-root-superclass class) | |
402 | ||
403 | ;; Check that the metaclass is a subclass of each direct superclass's | |
404 | ;; metaclass. | |
405 | (with-slots (metaclass direct-superclasses) class | |
406 | (dolist (super direct-superclasses) | |
407 | (unless (sod-subclass-p metaclass (sod-class-metaclass super)) | |
408 | (error "Incompatible metaclass for `~A': ~ | |
409 | `~A' isn't a subclass of `~A' (of `~A')" | |
410 | class metaclass (sod-class-metaclass super) super)))))) | |
411 | ||
412 | ;;;-------------------------------------------------------------------------- | |
413 | ;;; Finalization. | |
414 | ||
32bb097f MW |
415 | (defmethod finalize-sod-class :around ((class sod-class)) |
416 | "Common functionality for `finalize-sod-class'. | |
dea4d055 | 417 | |
32bb097f MW |
418 | * If an attempt to finalize the CLASS has been made before, then we |
419 | don't try again. Similarly, attempts to finalize a class recursively | |
420 | will fail. | |
dea4d055 | 421 | |
32bb097f MW |
422 | * A condition handler is established to keep track of whether any errors |
423 | are signalled during finalization. The CLASS is only marked as | |
424 | successfully finalized if no (unhandled) errors are encountered." | |
dea4d055 MW |
425 | (with-default-error-location (class) |
426 | (ecase (sod-class-state class) | |
427 | ((nil) | |
428 | ||
32bb097f | 429 | ;; If this fails, leave the class marked as a loss. |
16f9fb72 | 430 | (setf (slot-value class 'state) :broken) |
dea4d055 | 431 | |
32bb097f MW |
432 | ;; Invoke the finalization method proper. |
433 | (call-next-method) | |
16f9fb72 | 434 | (setf (slot-value class 'state) :finalized) |
dea4d055 MW |
435 | t) |
436 | ||
32bb097f | 437 | ;; If the class is broken, we're not going to be able to fix it now. |
dea4d055 MW |
438 | (:broken |
439 | nil) | |
440 | ||
32bb097f | 441 | ;; If we already finalized it, there's no point doing it again. |
dea4d055 MW |
442 | (:finalized |
443 | t)))) | |
abdf50aa | 444 | |
32bb097f MW |
445 | (defmethod finalize-sod-class ((class sod-class)) |
446 | ||
447 | ;; CLONE-AND-HACK WARNING: Note that `bootstrap-classes' has a (very brief) | |
448 | ;; clone of the CPL and chain establishment code. If the interface changes | |
449 | ;; then `bootstrap-classes' will need to be changed too. | |
450 | ||
451 | ;; Set up the metaclass if it's not been set already. This is delayed | |
452 | ;; to give bootstrapping a chance to set up metaclass and superclass | |
453 | ;; circularities. | |
454 | (default-slot (class 'metaclass) (guess-metaclass class)) | |
455 | ||
456 | ;; Finalize all of the superclasses. There's some special pleading here to | |
457 | ;; make bootstrapping work: we don't try to finalize the metaclass if we're | |
458 | ;; a root class (no direct superclasses -- because in that case the | |
459 | ;; metaclass will have to be a subclass of us!), or if it's equal to us. | |
460 | ;; This is enough to tie the knot at the top of the class graph. | |
461 | (with-slots (name direct-superclasses metaclass) class | |
462 | (dolist (super direct-superclasses) | |
463 | (finalize-sod-class super)) | |
464 | (unless (or (null direct-superclasses) | |
465 | (eq class metaclass)) | |
466 | (finalize-sod-class metaclass))) | |
467 | ||
468 | ;; Stash the class's type. | |
469 | (setf (slot-value class '%type) | |
470 | (make-class-type (sod-class-name class))) | |
471 | ||
472 | ;; Clobber the lists of items if they've not been set. | |
473 | (dolist (slot '(slots instance-initializers class-initializers | |
474 | messages methods)) | |
475 | (unless (slot-boundp class slot) | |
476 | (setf (slot-value class slot) nil))) | |
477 | ||
478 | ;; If the CPL hasn't been done yet, compute it. | |
479 | (with-slots (class-precedence-list) class | |
480 | (unless (slot-boundp class 'class-precedence-list) | |
481 | (setf class-precedence-list (compute-cpl class)))) | |
482 | ||
483 | ;; Check that the class is fairly sane. | |
484 | (check-sod-class class) | |
485 | ||
486 | ;; Determine the class's layout. | |
487 | (setf (values (slot-value class 'chain-head) | |
488 | (slot-value class 'chain) | |
489 | (slot-value class 'chains)) | |
490 | (compute-chains class))) | |
491 | ||
abdf50aa | 492 | ;;;----- That's all, folks -------------------------------------------------- |