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1 | ;;; -*-lisp-*- |
2 | ;;; | |
3 | ;;; Maintenance and recalculation of dependent values | |
4 | ;;; | |
5 | ;;; (c) 2008 Mark Wooding | |
6 | ;;; | |
7 | ||
8 | ;;;----- Licensing notice --------------------------------------------------- | |
9 | ;;; | |
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. | |
14 | ;;; | |
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. | |
19 | ;;; | |
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. | |
23 | ||
24 | (defpackage #:dep | |
5f61c961 | 25 | (:use #:common-lisp #:queue #:weak) |
af33e77c MW |
26 | (:export #:dep #:depp #:make-dep #:dep-goodp #:dep-name |
27 | #:with-deps-frozen | |
2626af66 MW |
28 | #:install-dep-syntax |
29 | #:dep-value #:dep-make-bad #:dep-bad #:dep-try | |
30 | #:dep-add-listener)) | |
31 | (in-package #:dep) | |
32 | ||
33 | ;;;-------------------------------------------------------------------------- | |
af33e77c MW |
34 | ;;; Constants. |
35 | ||
36 | (defconstant +value+ 1 | |
37 | "Flag: dep's value is up-to-date.") | |
38 | (defconstant +deps+ 2 | |
39 | "Flag: dep is known as a dependent on its dependencies.") | |
40 | (defconstant +changed+ 4 | |
41 | "Flag: dep has changed in the current recomputation phase.") | |
42 | (defconstant +recomputing+ 8 | |
43 | "Flag: dep is currently being recomputed.") | |
44 | (defconstant +queued+ 16 | |
45 | "Flag: dep is currently on the queue for recomputation.") | |
46 | ||
47 | (defconstant .bad. '.bad. | |
48 | "Magical value used to indicate bad deps.") | |
49 | ||
50 | ;;;-------------------------------------------------------------------------- | |
51 | ;;; Global and special variables. | |
2626af66 | 52 | |
23bc61bd MW |
53 | (defvar *generation* (list '*generation*) |
54 | "Generation marker, used to remember when we last updated a particular dep. | |
55 | Essentially, if the dep's generation matches *GENERATION* then it doesn't | |
56 | need updating again.") | |
57 | ||
58 | (defvar *evaluating-dep* nil | |
59 | "The dep currently being evaluated. This is bound only during the call of | |
af33e77c | 60 | a value-function, and is used to track the dependencies implied during the |
23bc61bd MW |
61 | function's evaluation.") |
62 | ||
af33e77c MW |
63 | (defvar *state* :ready |
64 | "The current state. It may be any of: | |
65 | ||
66 | * :READY -- the usual state: everything is up-to-date and correct. | |
67 | ||
68 | * :FROZEN -- the state used to evaluate the body of WITH-DEPS-FROZEN. | |
69 | Deps may be assigned values, but their dependents are not immediately | |
70 | recomputed. | |
71 | ||
72 | * :RECOMPUTING -- the state imposed while updating dependents.") | |
73 | ||
74 | (defvar *delayed-operations* nil | |
75 | "A queue of operations delayed by WITH-DEPS-FROZEN. Only available in the | |
76 | :RECOMPUTING state.") | |
77 | ||
23bc61bd MW |
78 | (defvar *pending-deps* nil |
79 | "A queue of deps pending recomputation. This is bound to a queue during | |
80 | recomputation and restored afterwards, so it can also be used as a flag to | |
af33e77c MW |
81 | detect whether recomputation is happening. |
82 | ||
83 | Deps on the queue are always in the current generation, and have the | |
84 | +QUEUED+ flag set.") | |
85 | ||
86 | ;;;-------------------------------------------------------------------------- | |
87 | ;;; Data structures. | |
23bc61bd | 88 | |
2626af66 MW |
89 | (defstruct (dep (:predicate depp) |
90 | (:constructor %make-dep)) | |
91 | "There are two kinds of `dep', though we use the same object type for both. | |
92 | A leaf dep has no dependencies, and its value is set explicitly by the | |
93 | programmer. A non-leaf dep has a value /function/, which computes the | |
94 | dep's value as a function of other deps' values. The dependencies don't | |
95 | need to be declared in advance, or remain constant over time. | |
96 | ||
97 | When not during a recomputation phase (i.e., when `stable'), a dep is | |
98 | either `good' (i.e., it has a value) or `bad'. An attempt to read the | |
99 | value of a bad dep results in a throw of `bad-dep'. Badness propagates | |
100 | automatically during recomputation phases." | |
af33e77c MW |
101 | (%value .bad. :type t) |
102 | (name nil :type t) | |
103 | (value-function nil :type (or function null)) | |
2626af66 | 104 | (value-predicate #'eql :type function) |
af33e77c | 105 | (%flags 0 :type (unsigned-byte 8)) |
23bc61bd | 106 | (generation *generation* :type list) |
2626af66 | 107 | (listeners nil :type list) |
5f61c961 | 108 | (dependents nil :type list) |
af33e77c | 109 | (dependencies nil :type list) |
5f61c961 | 110 | (weak-pointer nil :type t)) |
2626af66 | 111 | |
af33e77c MW |
112 | ;;;-------------------------------------------------------------------------- |
113 | ;;; Main code. | |
114 | ||
115 | (declaim (inline dep-flags)) | |
116 | (defun dep-flags (dep) | |
117 | "Return the current flags of DEP. | |
118 | ||
119 | The flags are fetched from the object if we're in a recomputation phase | |
120 | and the object's generation is current. Otherwise the object's flags are | |
121 | out of date, and we make up a better set." | |
122 | (cond ((eq *state* :ready) (logior +value+ +deps+)) | |
123 | ((eq (dep-generation dep) *generation*) (dep-%flags dep)) | |
124 | ((not (dep-value-function dep)) (logior +value+ +deps+)) | |
125 | (t 0))) | |
126 | ||
127 | (declaim (inline (setf dep-flags))) | |
128 | (defun (setf dep-flags) (flags dep) | |
129 | "Set the DEP's flags. | |
130 | ||
131 | This doesn't do anything else like force DEP's generation." | |
132 | (setf (dep-%flags dep) flags)) | |
133 | ||
134 | (defun update-dep (dep value) | |
135 | "Modify the value of DEP. | |
136 | ||
137 | If DEP's value is now different (according to its badness or | |
138 | value-predicate) then return true; otherwise return false." | |
139 | (let ((old-value (dep-%value dep))) | |
140 | (if (if (eq value .bad.) | |
141 | (eq old-value .bad.) | |
142 | (and (not (eq old-value .bad.)) | |
143 | (funcall (dep-value-predicate dep) value old-value))) | |
144 | nil | |
145 | (progn (setf (dep-%value dep) value) t)))) | |
146 | ||
147 | (defun new-dep-value (dep) | |
148 | "Recompute and return the value of DEP, or .BAD. if the dep is bad. | |
149 | ||
150 | This function is very minimal. The caller expected to deal with many | |
151 | aspects of caring for and feeding DEP. In particular: | |
152 | ||
153 | * Non-local exits (except throwing DEP-BAD) are not handled here. | |
154 | ||
155 | * We assume that DEP is already in the current generation, and has its | |
156 | +RECOMPUTING+ flag set. | |
157 | ||
158 | * The caller is responsible for setting the current flags afterwards." | |
159 | (catch 'dep-bad | |
160 | (let ((*evaluating-dep* dep)) | |
161 | (setf (dep-dependencies dep) nil) | |
162 | (funcall (dep-value-function dep))))) | |
163 | ||
164 | (defun propagate-to-dependents (dep) | |
165 | "Notify the dependents of DEP of a change to its value. | |
166 | ||
167 | We assume that DEP is up-to-date in the current generation, and has | |
168 | correct flags (at least +VALUE+ and +CHANGED+, and maybe +DEPS+). | |
169 | Dependents of DEP are enqueued for recomputation. The DEP's dependents | |
170 | are forced into the current generation and enqueued, and the dependents | |
171 | list is cleared ready to be repopulated. The DEP's listener functions are | |
172 | invoked." | |
5f61c961 MW |
173 | (dolist (dweak (dep-dependents dep)) |
174 | (let ((d (weak-pointer-value dweak))) | |
af33e77c MW |
175 | (when d |
176 | (let ((flags (dep-flags d))) | |
177 | (unless (plusp (logand flags (logior +queued+ +deps+))) | |
178 | (enqueue d *pending-deps*) | |
179 | (setf (dep-generation d) *generation* | |
180 | (dep-flags d) (logior (logand flags +value+) | |
181 | +queued+))))))) | |
2626af66 | 182 | (setf (dep-dependents dep) nil) |
af33e77c MW |
183 | (dolist (listener (dep-listeners dep)) |
184 | (funcall listener))) | |
185 | ||
186 | (defun recompute-dep-value (dep) | |
187 | "Recompute the value of DEP. | |
188 | ||
189 | Returns true if DEP's value actually changed, or nil otherwise. On exit, | |
190 | the DEP's +VALUE+ and +DEPS+ flags are set, and +CHANGED+ is set if the | |
191 | value actually changed. | |
192 | ||
193 | We assume that DEP's dependencies are up-to-date already, and that DEP's | |
194 | +RECOMPUTING+ flag is set. In the former case, DEP's dependents and | |
195 | listeners are notified, using PROPAGATE-TO-DEPENDENTS." | |
196 | (let ((winning nil) (queued (logand (dep-%flags dep) +queued+))) | |
197 | (flet ((update (value) | |
198 | (cond ((update-dep dep value) | |
199 | (setf (dep-flags dep) (logior +value+ +deps+ +changed+ | |
200 | queued)) | |
201 | (propagate-to-dependents dep) | |
202 | t) | |
203 | (t | |
204 | (setf (dep-flags dep) (logior +value+ +deps+ queued)) | |
205 | nil)))) | |
23bc61bd | 206 | (unwind-protect |
af33e77c MW |
207 | (prog1 (update (new-dep-value dep)) (setf winning t)) |
208 | (unless winning (update .bad.)))))) | |
209 | ||
210 | (defun force-dep-value (dep) | |
211 | "Arrange for DEP to have a current value. | |
212 | ||
213 | Returns true if the DEP's value has changed in this recomputation phase, | |
214 | or nil if not. | |
215 | ||
216 | If DEP is already has a good value, then we just use that; the return | |
217 | value is determined by the +CHANGED+ flag. Otherwise, we set | |
218 | +RECOMPUTING+ (in order to trap circularities) and force the values of | |
219 | DEP's dependencies in turn. If any of them returned true then we have to | |
220 | explicitly recompute DEP (so we do); otherwise we can leave it as it is." | |
221 | (let ((flags (dep-flags dep))) | |
222 | (cond ((plusp (logand flags +recomputing+)) | |
223 | (error "Ouch! Circular dependency detected.")) | |
224 | ((plusp (logand flags +value+)) | |
225 | (plusp (logand flags +changed+))) | |
226 | (t | |
227 | (setf (dep-generation dep) *generation* | |
228 | (dep-flags dep) (logior (logand flags +queued+) | |
229 | +recomputing+)) | |
230 | (if (some #'force-dep-value (dep-dependencies dep)) | |
231 | (recompute-dep-value dep) | |
232 | (progn (setf (dep-flags dep) flags) nil)))))) | |
233 | ||
234 | (defun %dep-value (dep) | |
235 | "Do the difficult work of retrieving the current value of a DEP." | |
236 | (when *evaluating-dep* | |
237 | (pushnew (dep-weak-pointer *evaluating-dep*) (dep-dependents dep)) | |
238 | (pushnew dep (dep-dependencies *evaluating-dep*))) | |
239 | (force-dep-value dep)) | |
240 | ||
241 | (declaim (inline dep-value)) | |
242 | (defun dep-value (dep) | |
243 | "Retrieve the current value from DEP." | |
244 | (when (eq *state* :recomputing) | |
245 | (%dep-value dep)) | |
246 | (let ((value (dep-%value dep))) | |
247 | (if (eq value .bad.) | |
248 | (throw 'dep-bad .bad.) | |
249 | value))) | |
250 | ||
251 | (defun dep-goodp (dep) | |
252 | "Answer whether DEP is good." | |
253 | (when (eq *state* :recomputing) | |
254 | (force-dep-value dep)) | |
255 | (not (eq (dep-%value dep) .bad.))) | |
256 | ||
257 | (defmacro dep-try (expr &body body) | |
258 | "Evaluate EXPR. If it throws DEP-BAD then evaluate BODY instead." | |
259 | (let ((block-name (gensym "TRY"))) | |
260 | `(block ,block-name | |
261 | (catch 'dep-bad | |
262 | (return-from ,block-name ,expr)) | |
263 | ,@body))) | |
264 | ||
265 | (defun dep-bad () | |
266 | "Call from a value-function: indicates that the dep should marked as bad." | |
267 | (throw 'dep-bad nil)) | |
268 | ||
269 | (defun recompute-pending-deps () | |
270 | "Process the *PENDING-DEPS* queue, recomputing the deps listed on it. | |
271 | ||
272 | We bind *STATE* to :RECOMPUTING during the process." | |
273 | (let ((*state* :recomputing)) | |
274 | (unwind-protect | |
275 | (loop (when (queue-emptyp *pending-deps*) | |
276 | (return)) | |
277 | (let* ((dep (dequeue *pending-deps*)) | |
278 | (flags (dep-%flags dep))) | |
279 | (setf (dep-%flags dep) (logandc2 flags +queued+)) | |
280 | (cond ((zerop (logand flags +value+)) | |
281 | (recompute-dep-value dep)) | |
282 | ((zerop (logand flags +deps+)) | |
283 | (new-dep-value dep) | |
284 | (setf (dep-%flags dep) (logior flags +deps+)))))) | |
285 | (loop (when (queue-emptyp *pending-deps*) | |
286 | (return)) | |
287 | (let ((d (dequeue *pending-deps*))) | |
288 | (setf (dep-%value d) .bad.)))))) | |
289 | ||
290 | (defun with-deps-frozen* (thunk &key delay) | |
291 | "Invoke THUNK in the :FROZEN state. See WITH-DEPS-FROZEN for full | |
292 | information." | |
293 | (ecase *state* | |
294 | (:frozen | |
295 | (funcall thunk)) | |
2626af66 | 296 | (:recomputing |
af33e77c MW |
297 | (unless delay |
298 | (error "This really isn't a good time.")) | |
299 | (enqueue thunk *delayed-operations*)) | |
300 | (:ready | |
301 | (let ((*state* :frozen) | |
302 | (*delayed-operations* (make-queue)) | |
303 | (*pending-deps* (make-queue))) | |
304 | (setf *generation* (list '*generation*)) | |
305 | (multiple-value-prog1 (funcall thunk) | |
306 | (loop (recompute-pending-deps) | |
307 | (when (queue-emptyp *delayed-operations*) | |
308 | (return)) | |
309 | (funcall (dequeue *delayed-operations*)))))))) | |
310 | ||
311 | (defmacro with-deps-frozen ((&key delay) &body body) | |
312 | "Evaluate BODY in the :FROZEN state. | |
313 | ||
314 | In the :FROZEN state, recomutation is deferred. If the current state is | |
315 | :READY, then we enter :FROZEN, evaluate the BODY, and then enter | |
316 | :RECOMPUTING to fix up the dependency graph. If the current state is | |
317 | :FROZEN, we do nothing particularly special. Finally, if the current | |
318 | state is :RECOMPUTING then the behaviour depends on the value of | |
319 | the :DELAY argument: if false, an error is signalled; if true, the | |
320 | evaluation is postponed until the end of the recomputation. | |
321 | ||
322 | This macro has four immediate uses. | |
323 | ||
324 | * Firstly, it's actually the only way to trigger recomputation at all. | |
325 | It's invoked behind the scenes to do the right thing. | |
326 | ||
327 | * If you're making a large number of updates without data dependencies | |
328 | then you can make them go faster by wrapping them in WITH-DEPS-FROZEN | |
329 | and only having a single recomputation phase. | |
330 | ||
331 | * A simple (SETF (DEP-VALUE ...) ...) is unsafe during recomputation. | |
332 | You can use WITH-DEPS-FROZEN to indicate that it's safe to defer the | |
333 | assignment until later. Deferred operations take place in the order | |
334 | in which they were requested. | |
335 | ||
336 | * Finally, you can use it to force a number of deps to hold given values | |
337 | simultaneously, despite their value-functions disagreeing." | |
338 | `(with-deps-frozen* (lambda () ,@body) :delay ,delay)) | |
2626af66 MW |
339 | |
340 | (defun (setf dep-value) (value dep) | |
af33e77c MW |
341 | "Assign the VALUE to the DEP, forcing recomputation if necessary." |
342 | (with-deps-frozen () | |
343 | (when (update-dep dep value) | |
344 | (setf (dep-generation dep) *generation* | |
345 | (dep-flags dep) (logior +value+ +changed+)) | |
346 | (propagate-to-dependents dep))) | |
2626af66 MW |
347 | value) |
348 | ||
349 | (defun dep-make-bad (dep) | |
350 | "Mark DEP as being bad." | |
af33e77c | 351 | (setf (dep-value dep) .bad.)) |
2626af66 MW |
352 | |
353 | (defun dep-add-listener (dep func) | |
354 | "Add a listener function FUNC to the DEP. The FUNC is called each time the | |
355 | DEP's value (or good/bad state) changes. It is called with no arguments, | |
356 | and its return value is ignored." | |
357 | (push func (dep-listeners dep))) | |
358 | ||
2626af66 MW |
359 | (defun make-dep (&rest args) |
360 | "Create a new DEP object. There are two basic argument forms: | |
361 | ||
23bc61bd | 362 | (:value &optional OBJECT) |
2626af66 | 363 | Return a leaf dep, whose value is OBJECT; if no OBJECT is given, the |
af33e77c | 364 | dep is initially bad. The keyword :LEAF is accepted as a synonym. |
2626af66 MW |
365 | |
366 | (:function FUNCTION) | |
367 | Return a non-leaf dep whose value is computed by FUNCTION. | |
368 | ||
23bc61bd MW |
369 | Additionally, if the first argument is something other than :VALUE or |
370 | :FUNCTION (ideally not a keyword, for forward compatibility), then the | |
2626af66 MW |
371 | first argument is inspected: if it's a function, then a function dep is |
372 | retuerned (as if you'd specified :function); otherwise a leaf dep is | |
373 | returned. | |
374 | ||
af33e77c | 375 | Finally, it's possible to specify both :VALUE and :FUNCTION |
23bc61bd MW |
376 | simultaneously; this will set the initial values as requested, but |
377 | recompute them as necessary. It is possible to establish dependency | |
378 | cycles, but you need to suppress recomputation in order to do this | |
379 | correctly -- see the DELAY-RECOMPUTING-DEPS macro. | |
380 | ||
2626af66 MW |
381 | If no arguments are given, a bad leaf dep is returned." |
382 | ||
23bc61bd MW |
383 | (flet ((arg () (if args (pop args) |
384 | (error "Not enough arguments to MAKE-DEP.")))) | |
2626af66 MW |
385 | |
386 | ;; Sort out the arguments. | |
af33e77c | 387 | (let ((value .bad.) |
23bc61bd | 388 | (valuep nil) |
af33e77c | 389 | (name nil) |
5f61c961 | 390 | (predicate #'eql) |
af33e77c | 391 | (listeners nil) |
23bc61bd MW |
392 | (function nil)) |
393 | (do () ((endp args)) | |
394 | (let ((indicator (pop args))) | |
5f61c961 MW |
395 | (case indicator |
396 | ((:value :leaf) | |
af33e77c MW |
397 | (setf value (if args (pop args) .bad.) |
398 | valuep t)) | |
5f61c961 MW |
399 | (:function |
400 | (setf function (arg))) | |
401 | (:predicate | |
402 | (setf predicate (arg))) | |
af33e77c MW |
403 | (:name |
404 | (setf name (arg))) | |
405 | (:listener | |
406 | (push (arg) listeners)) | |
5f61c961 MW |
407 | (t |
408 | (cond ((functionp indicator) | |
409 | (setf function indicator)) | |
410 | (t | |
af33e77c MW |
411 | (setf value indicator |
412 | valuep t))))))) | |
413 | (unless (or valuep function) | |
414 | (setf valuep t)) | |
2626af66 MW |
415 | |
416 | ;; Create the object appropriately. | |
af33e77c | 417 | (let ((dep (%make-dep :value-function function |
23bc61bd | 418 | :%value value |
af33e77c MW |
419 | :name name |
420 | :listeners listeners | |
421 | :%flags (logior (if valuep +value+ 0) | |
422 | (if function +queued+ +deps+) | |
423 | +changed+) | |
5f61c961 | 424 | :value-predicate predicate |
af33e77c | 425 | :generation *generation*))) |
5f61c961 | 426 | (setf (dep-weak-pointer dep) (make-weak-pointer dep)) |
af33e77c MW |
427 | (when function |
428 | (with-deps-frozen () | |
429 | (enqueue dep *pending-deps*))) | |
430 | dep)))) | |
2626af66 MW |
431 | |
432 | (defun install-dep-syntax (&optional (readtable *readtable*)) | |
433 | "Installs into the given READTABLE some syntactic shortcuts: | |
434 | ||
435 | ?FORM -> (dep-value FORM) | |
436 | Extract (or modify, for a leaf dep) the value of the dep indicated by | |
437 | FORM. | |
438 | ||
439 | #[FORM ...] -> (make-dep :funcion (lambda () FORM ...)) | |
440 | Return a derived dep whose value function computes the given FORMs | |
441 | (as an implicit PROGN) | |
442 | ||
443 | Returns the READTABLE." | |
444 | (set-macro-character #\? | |
445 | (lambda (stream char) | |
446 | (declare (ignore char)) | |
447 | (list 'dep-value (read stream t nil t))) | |
448 | readtable) | |
449 | (set-syntax-from-char #\] #\) readtable readtable) | |
450 | (set-dispatch-macro-character #\# #\[ | |
451 | (lambda (stream arg char) | |
452 | (declare (ignore arg char)) | |
453 | `(make-dep :function | |
454 | (lambda () | |
455 | ,@(read-delimited-list #\] | |
456 | stream | |
457 | t)))) | |
458 | readtable) | |
459 | readtable) | |
460 | ||
af33e77c | 461 | #- abcl |
2626af66 MW |
462 | (defmethod print-object ((dep dep) stream) |
463 | (print-unreadable-object (dep stream :type t :identity t) | |
af33e77c MW |
464 | (pprint-logical-block (stream nil) |
465 | (let ((flags (dep-flags dep)) | |
466 | (value (dep-%value dep))) | |
467 | (cond ((zerop (logand flags +value+)) | |
468 | (write-string "#<out-of-date>" stream)) | |
469 | ((eq value .bad.) | |
470 | (write-string "#<bad>" stream)) | |
471 | (t | |
472 | (write value :stream stream))) | |
473 | (when (dep-name dep) | |
474 | (format stream " ~_~S ~@_~W" :name (dep-name dep))) | |
475 | (when (zerop (logand flags +deps+)) | |
476 | (format stream " ~_~S" :recompute-deps)) | |
477 | (when (plusp (logand flags +queued+)) | |
478 | (format stream " ~_~S" :queued)) | |
479 | (when (plusp (logand flags +changed+)) | |
480 | (format stream " ~_~S" :changed)))))) | |
481 | ||
482 | ;;;-------------------------------------------------------------------------- | |
483 | ;;; Tests. | |
2626af66 MW |
484 | |
485 | #+ test | |
486 | (progn | |
af33e77c MW |
487 | (defparameter x (make-dep :name 'x 1)) |
488 | (defparameter y (make-dep :name 'y 2)) | |
489 | (defparameter z (make-dep :name 'z | |
490 | (lambda () (+ (dep-value x) (dep-value y))))) | |
491 | (defparameter w (make-dep :name 'w | |
492 | (lambda () (* (dep-value x) (dep-value z))))) | |
2626af66 MW |
493 | (dep-add-listener x (lambda () (format t "x now ~A~%" x))) |
494 | (dep-add-listener z (lambda () (format t "z now ~A~%" z))) | |
495 | (dep-add-listener w (lambda () (format t "w now ~A~%" w)))) | |
496 | ||
af33e77c MW |
497 | #+ test |
498 | (progn | |
499 | (defparameter a (make-dep :name 'a 1)) | |
500 | (defparameter b (make-dep :name 'b 2)) | |
501 | (defparameter c (make-dep :name 'c | |
502 | (lambda () (1+ (dep-value a))))) | |
503 | (defparameter d (make-dep :name 'd | |
504 | (lambda () (* (dep-value c) (dep-value b))))) | |
505 | (defparameter e (make-dep :name 'e | |
506 | (lambda () (- (dep-value d) (dep-value a))))) | |
507 | ;; a b c = a + 1 d = c*b e = d - a | |
508 | ;; 1 2 2 4 3 | |
509 | ;; 4 2 5 10 6 | |
510 | (values (dep-value e) | |
511 | (progn | |
512 | (setf (dep-value a) 4) | |
513 | (dep-value e)))) | |
514 | ||
515 | #+ test | |
516 | (progn | |
517 | (defparameter x nil) | |
518 | (defparameter y nil) | |
519 | (with-deps-frozen () | |
520 | (setf x (make-dep :name 'x 1 (lambda () (+ (dep-value y) 1))) | |
521 | y (make-dep :name 'y 2 (lambda () (- (dep-value x) 2)))))) | |
522 | ||
523 | #+ test | |
524 | (trace with-deps-frozen* update-dep new-dep-value force-dep-value | |
525 | recompute-dep-value recompute-pending-deps propagate-to-dependents | |
526 | dep-value) | |
527 | ||
2626af66 | 528 | ;;;----- That's all, folks -------------------------------------------------- |