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3b1e4dd1 | 1 | ;;; cust-print.el --- handles print-level and print-circle. |
ecb4184d | 2 | |
9750e079 ER |
3 | ;; Copyright (C) 1992 Free Software Foundation, Inc. |
4 | ||
e5167999 ER |
5 | ;; Author: Daniel LaLiberte <liberte@cs.uiuc.edu> |
6 | ;; Version: 1.0 | |
e5167999 | 7 | ;; Adapted-By: ESR |
e9571d2a | 8 | ;; Keywords: extensions |
ecb4184d | 9 | |
ecb4184d ER |
10 | ;; This file is part of GNU Emacs. |
11 | ||
12 | ;; GNU Emacs is free software; you can redistribute it and/or modify | |
13 | ;; it under the terms of the GNU General Public License as published by | |
e5167999 | 14 | ;; the Free Software Foundation; either version 2, or (at your option) |
ecb4184d ER |
15 | ;; any later version. |
16 | ||
17 | ;; GNU Emacs 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 GNU Emacs; see the file COPYING. If not, write to | |
24 | ;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. | |
25 | ||
e5167999 ER |
26 | ;;; Commentary: |
27 | ||
ecb4184d ER |
28 | ;; This package provides a general print handler for prin1 and princ |
29 | ;; that supports print-level and print-circle, and by the way, | |
30 | ;; print-length since the standard routines are being replaced. Also, | |
31 | ;; to print custom types constructed from lists and vectors, use | |
32 | ;; custom-print-list and custom-print-vector. See the documentation | |
33 | ;; strings of these variables for more details. | |
34 | ||
35 | ;; If the results of your expressions contain circular references to | |
36 | ;; other parts of the same structure, the standard Emacs print | |
37 | ;; subroutines may fail to print with an untrappable error, | |
38 | ;; "Apparently circular structure being printed". If you only use cdr | |
39 | ;; circular lists (where cdrs of lists point back; what is the right | |
40 | ;; term here?), you can limit the length of printing with | |
41 | ;; print-length. But car circular lists and circular vectors generate | |
42 | ;; the above mentioned untrappable error in Emacs version 18. Version | |
43 | ;; 19 will support print-level, but it is often useful to get a better | |
44 | ;; print representation of circular structures; the print-circle | |
45 | ;; option may be used to print more concise representations. | |
46 | ||
47 | ;; There are two main ways to use this package. First, you may | |
48 | ;; replace prin1, princ, and some subroutines that use them by calling | |
49 | ;; install-custom-print-funcs so that any use of these functions in | |
50 | ;; lisp code will be affected. Second, you could call the custom | |
51 | ;; routines directly, thus only affecting the printing that requires | |
52 | ;; them. | |
53 | ||
54 | ;; Note that subroutines which call print subroutines directly will not | |
55 | ;; use the custom print functions. In particular, the evaluation | |
56 | ;; functions like eval-region call the print subroutines directly. | |
57 | ;; Therefore, evaluating (aref circ-list 0), which calls error | |
58 | ;; directly (because circ-list is not an array), will jump to the top | |
59 | ;; level instead of printing the circular list. | |
60 | ||
61 | ;; Obviously the right way to implement this custom-print facility | |
62 | ;; is in C. Please volunteer since I don't have the time or need. | |
63 | ||
64 | ;; Implementation design: we want to use the same list and vector | |
65 | ;; processing algorithm for all versions of prin1 and princ, since how | |
66 | ;; the processing is done depends on print-length, print-level, and | |
67 | ;; print-circle. For circle printing, a preprocessing step is | |
68 | ;; required before the final printing. Thanks to Jamie Zawinski | |
69 | ;; for motivation and algorithms. | |
70 | ||
71 | ;;========================================================= | |
72 | ;; export list: | |
73 | ||
74 | ;; print-level | |
75 | ;; print-circle | |
76 | ||
77 | ;; custom-print-list | |
78 | ;; custom-print-vector | |
79 | ;; add-custom-print-list | |
80 | ;; add-custom-print-vector | |
81 | ||
82 | ;; install-custom-print-funcs | |
83 | ;; uninstall-custom-print-funcs | |
84 | ||
85 | ;; custom-prin1 | |
86 | ;; custom-princ | |
87 | ;; custom-prin1-to-string | |
88 | ;; custom-print | |
89 | ;; custom-format | |
90 | ;; custom-message | |
91 | ;; custom-error | |
92 | ||
e5167999 | 93 | ;;; Code: |
ecb4184d ER |
94 | |
95 | (provide 'custom-print) | |
ecb4184d ER |
96 | |
97 | ;;(defvar print-length nil | |
98 | ;; "*Controls how many elements of a list, at each level, are printed. | |
99 | ;;This is defined by emacs.") | |
100 | ||
101 | (defvar print-level nil | |
102 | "*Controls how many levels deep a nested data object will print. | |
103 | ||
104 | If nil, printing proceeds recursively and may lead to | |
105 | max-lisp-eval-depth being exceeded or an untrappable error may occur: | |
fb252f97 RS |
106 | `Apparently circular structure being printed.' |
107 | Also see `print-length' and `print-circle'. | |
ecb4184d | 108 | |
fb252f97 | 109 | If non-nil, components at levels equal to or greater than `print-level' |
92ad69b6 | 110 | are printed simply as `#'. The object to be printed is at level 0, |
ecb4184d ER |
111 | and if the object is a list or vector, its top-level components are at |
112 | level 1.") | |
113 | ||
114 | ||
115 | (defvar print-circle nil | |
116 | "*Controls the printing of recursive structures. | |
117 | ||
118 | If nil, printing proceeds recursively and may lead to | |
fb252f97 | 119 | `max-lisp-eval-depth' being exceeded or an untrappable error may occur: |
ecb4184d | 120 | \"Apparently circular structure being printed.\" Also see |
fb252f97 | 121 | `print-length' and `print-level'. |
ecb4184d ER |
122 | |
123 | If non-nil, shared substructures anywhere in the structure are printed | |
eb8c3be9 JB |
124 | with `#N=' before the first occurrence (in the order of the print |
125 | representation) and `#N#' in place of each subsequent occurrence, | |
fb252f97 | 126 | where N is a positive decimal integer. |
ecb4184d ER |
127 | |
128 | Currently, there is no way to read this representation in Emacs.") | |
129 | ||
130 | ||
131 | (defconst custom-print-list | |
132 | nil | |
133 | ;; e.g. '((floatp . float-to-string)) | |
fb252f97 RS |
134 | "An alist for custom printing of lists. |
135 | Pairs are of the form (PRED . CONVERTER). If PREDICATE is true | |
136 | for an object, then CONVERTER is called with the object and should | |
137 | return a string to be printed with `princ'. | |
138 | Also see `custom-print-vector'.") | |
ecb4184d ER |
139 | |
140 | (defconst custom-print-vector | |
141 | nil | |
fb252f97 RS |
142 | "An alist for custom printing of vectors. |
143 | Pairs are of the form (PRED . CONVERTER). If PREDICATE is true | |
144 | for an object, then CONVERTER is called with the object and should | |
145 | return a string to be printed with `princ'. | |
146 | Also see `custom-print-list'.") | |
ecb4184d ER |
147 | |
148 | ||
149 | (defun add-custom-print-list (pred converter) | |
fb252f97 | 150 | "Add a pair of PREDICATE and CONVERTER to `custom-print-list'. |
ecb4184d ER |
151 | Any pair that has the same PREDICATE is first removed." |
152 | (setq custom-print-list (cons (cons pred converter) | |
153 | (delq (assq pred custom-print-list) | |
154 | custom-print-list)))) | |
155 | ;; e.g. (add-custom-print-list 'floatp 'float-to-string) | |
156 | ||
157 | ||
158 | (defun add-custom-print-vector (pred converter) | |
fb252f97 | 159 | "Add a pair of PREDICATE and CONVERTER to `custom-print-vector'. |
ecb4184d ER |
160 | Any pair that has the same PREDICATE is first removed." |
161 | (setq custom-print-vector (cons (cons pred converter) | |
162 | (delq (assq pred custom-print-vector) | |
163 | custom-print-vector)))) | |
164 | ||
165 | ||
166 | ;;==================================================== | |
167 | ;; Saving and restoring internal printing routines. | |
168 | ||
fb252f97 | 169 | (defun cust-print-set-function-cell (symbol-pair) |
31e1d920 | 170 | (defalias (car symbol-pair) |
ecb4184d ER |
171 | (symbol-function (car (cdr symbol-pair))))) |
172 | ||
173 | ||
fb252f97 RS |
174 | (if (not (fboundp 'cust-print-internal-prin1)) |
175 | (mapcar 'cust-print-set-function-cell | |
176 | '((cust-print-internal-prin1 prin1) | |
177 | (cust-print-internal-princ princ) | |
178 | (cust-print-internal-print print) | |
179 | (cust-print-internal-prin1-to-string prin1-to-string) | |
180 | (cust-print-internal-format format) | |
181 | (cust-print-internal-message message) | |
182 | (cust-print-internal-error error)))) | |
ecb4184d ER |
183 | |
184 | ||
185 | (defun install-custom-print-funcs () | |
fb252f97 RS |
186 | "Replace print functions with general, customizable, Lisp versions. |
187 | The internal subroutines are saved away, and you can reinstall them | |
188 | by running `uninstall-custom-print-funcs'." | |
ecb4184d | 189 | (interactive) |
fb252f97 | 190 | (mapcar 'cust-print-set-function-cell |
ecb4184d ER |
191 | '((prin1 custom-prin1) |
192 | (princ custom-princ) | |
193 | (print custom-print) | |
194 | (prin1-to-string custom-prin1-to-string) | |
195 | (format custom-format) | |
196 | (message custom-message) | |
197 | (error custom-error) | |
198 | ))) | |
199 | ||
200 | (defun uninstall-custom-print-funcs () | |
201 | "Reset print functions to their internal subroutines." | |
202 | (interactive) | |
fb252f97 RS |
203 | (mapcar 'cust-print-set-function-cell |
204 | '((prin1 cust-print-internal-prin1) | |
205 | (princ cust-print-internal-princ) | |
206 | (print cust-print-internal-print) | |
207 | (prin1-to-string cust-print-internal-prin1-to-string) | |
208 | (format cust-print-internal-format) | |
209 | (message cust-print-internal-message) | |
210 | (error cust-print-internal-error) | |
ecb4184d ER |
211 | ))) |
212 | ||
213 | ||
214 | ;;=============================================================== | |
215 | ;; Lisp replacements for prin1 and princ and for subrs that use prin1 | |
216 | ;; (or princ) -- so far only the printing and formatting subrs. | |
217 | ||
218 | (defun custom-prin1 (object &optional stream) | |
fb252f97 RS |
219 | "Replacement for standard `prin1'. |
220 | Uses the appropriate printer depending on the values of `print-level' | |
221 | and `print-circle' (which see). | |
ecb4184d ER |
222 | |
223 | Output the printed representation of OBJECT, any Lisp object. | |
224 | Quoting characters are printed when needed to make output that `read' | |
225 | can handle, whenever this is possible. | |
226 | Output stream is STREAM, or value of `standard-output' (which see)." | |
fb252f97 | 227 | (cust-print-top-level object stream 'cust-print-internal-prin1)) |
ecb4184d ER |
228 | |
229 | ||
230 | (defun custom-princ (object &optional stream) | |
fb252f97 RS |
231 | "Same as `custom-prin1' except no quoting." |
232 | (cust-print-top-level object stream 'cust-print-internal-princ)) | |
ecb4184d | 233 | |
92ad69b6 RS |
234 | (defvar custom-prin1-chars) |
235 | ||
ecb4184d | 236 | (defun custom-prin1-to-string-func (c) |
fb252f97 | 237 | "Stream function for `custom-prin1-to-string'." |
92ad69b6 | 238 | (setq custom-prin1-chars (cons c custom-prin1-chars))) |
ecb4184d ER |
239 | |
240 | (defun custom-prin1-to-string (object) | |
fb252f97 | 241 | "Replacement for standard `prin1-to-string'." |
92ad69b6 | 242 | (let ((custom-prin1-chars nil)) |
ecb4184d | 243 | (custom-prin1 object 'custom-prin1-to-string-func) |
92ad69b6 | 244 | (concat (nreverse custom-prin1-chars)))) |
ecb4184d ER |
245 | |
246 | ||
247 | (defun custom-print (object &optional stream) | |
fb252f97 RS |
248 | "Replacement for standard `print'." |
249 | (cust-print-internal-princ "\n") | |
ecb4184d | 250 | (custom-prin1 object stream) |
fb252f97 | 251 | (cust-print-internal-princ "\n")) |
ecb4184d ER |
252 | |
253 | ||
254 | (defun custom-format (fmt &rest args) | |
fb252f97 | 255 | "Replacement for standard `format'. |
ecb4184d ER |
256 | |
257 | Calls format after first making strings for list or vector args. | |
fb252f97 | 258 | The format specification for such args should be `%s' in any case, so a |
ecb4184d | 259 | string argument will also work. The string is generated with |
fb252f97 RS |
260 | `custom-prin1-to-string', which quotes quotable characters." |
261 | (apply 'cust-print-internal-format fmt | |
ecb4184d ER |
262 | (mapcar (function (lambda (arg) |
263 | (if (or (listp arg) (vectorp arg)) | |
264 | (custom-prin1-to-string arg) | |
265 | arg))) | |
266 | args))) | |
267 | ||
268 | ||
269 | ||
270 | (defun custom-message (fmt &rest args) | |
fb252f97 | 271 | "Replacement for standard `message' that works like `custom-format'." |
eb8c3be9 | 272 | ;; It doesn't work to princ the result of custom-format |
ecb4184d | 273 | ;; because the echo area requires special handling |
fb252f97 RS |
274 | ;; to avoid duplicating the output. cust-print-internal-message does it right. |
275 | ;; (cust-print-internal-princ (apply 'custom-format fmt args)) | |
276 | (apply 'cust-print-internal-message fmt | |
ecb4184d ER |
277 | (mapcar (function (lambda (arg) |
278 | (if (or (listp arg) (vectorp arg)) | |
279 | (custom-prin1-to-string arg) | |
280 | arg))) | |
281 | args))) | |
282 | ||
283 | ||
284 | (defun custom-error (fmt &rest args) | |
fb252f97 | 285 | "Replacement for standard `error' that uses `custom-format'" |
ecb4184d ER |
286 | (signal 'error (list (apply 'custom-format fmt args)))) |
287 | ||
288 | ||
289 | ;;========================================= | |
290 | ;; Support for custom prin1 and princ | |
291 | ||
92ad69b6 RS |
292 | (defvar circle-table) |
293 | (defvar circle-tree) | |
294 | (defvar circle-level) | |
295 | ||
fb252f97 | 296 | (defun cust-print-top-level (object stream internal-printer) |
ecb4184d ER |
297 | "Set up for printing." |
298 | (let ((standard-output (or stream standard-output)) | |
fb252f97 | 299 | (circle-table (and print-circle (cust-print-preprocess-circle-tree object))) |
92ad69b6 | 300 | (circle-level (or print-level -1)) |
ecb4184d ER |
301 | ) |
302 | ||
31e1d920 ER |
303 | (defalias 'cust-print-internal-printer internal-printer) |
304 | (defalias 'cust-print-low-level-prin | |
ecb4184d ER |
305 | (cond |
306 | ((or custom-print-list | |
307 | custom-print-vector | |
308 | print-level ; comment out for version 19 | |
309 | ) | |
fb252f97 | 310 | 'cust-print-custom-object) |
ecb4184d | 311 | (circle-table |
fb252f97 RS |
312 | 'cust-print-object) |
313 | (t 'cust-print-internal-printer))) | |
31e1d920 | 314 | (defalias 'cust-print-prin (if circle-table 'cust-print-circular 'cust-print-low-level-prin)) |
ecb4184d | 315 | |
fb252f97 | 316 | (cust-print-prin object) |
ecb4184d ER |
317 | object)) |
318 | ||
319 | ||
fb252f97 RS |
320 | ;; Test object type and print accordingly. |
321 | (defun cust-print-object (object) | |
322 | ;; Could be called as either cust-print-low-level-prin or cust-print-prin. | |
ecb4184d | 323 | (cond |
fb252f97 RS |
324 | ((null object) (cust-print-internal-printer object)) |
325 | ((consp object) (cust-print-list object)) | |
326 | ((vectorp object) (cust-print-vector object)) | |
ecb4184d | 327 | ;; All other types, just print. |
fb252f97 | 328 | (t (cust-print-internal-printer object)))) |
ecb4184d ER |
329 | |
330 | ||
fb252f97 RS |
331 | ;; Test object type and print accordingly. |
332 | (defun cust-print-custom-object (object) | |
333 | ;; Could be called as either cust-print-low-level-prin or cust-print-prin. | |
ecb4184d | 334 | (cond |
fb252f97 | 335 | ((null object) (cust-print-internal-printer object)) |
ecb4184d ER |
336 | |
337 | ((consp object) | |
338 | (or (and custom-print-list | |
fb252f97 RS |
339 | (cust-print-custom-object1 object custom-print-list)) |
340 | (cust-print-list object))) | |
ecb4184d ER |
341 | |
342 | ((vectorp object) | |
343 | (or (and custom-print-vector | |
fb252f97 RS |
344 | (cust-print-custom-object1 object custom-print-vector)) |
345 | (cust-print-vector object))) | |
ecb4184d ER |
346 | |
347 | ;; All other types, just print. | |
fb252f97 | 348 | (t (cust-print-internal-printer object)))) |
ecb4184d ER |
349 | |
350 | ||
fb252f97 RS |
351 | ;; Helper for cust-print-custom-object. |
352 | ;; Print the custom OBJECT using the custom type ALIST. | |
353 | ;; For the first predicate that matches the object, the corresponding | |
354 | ;; converter is evaluated with the object and the string that results is | |
eb8c3be9 | 355 | ;; printed with princ. Return nil if no predicate matches the object. |
fb252f97 | 356 | (defun cust-print-custom-object1 (object alist) |
ecb4184d ER |
357 | (while (and alist (not (funcall (car (car alist)) object))) |
358 | (setq alist (cdr alist))) | |
359 | ;; If alist is not null, then something matched. | |
360 | (if alist | |
fb252f97 | 361 | (cust-print-internal-princ |
ecb4184d ER |
362 | (funcall (cdr (car alist)) object) ; returns string |
363 | ))) | |
364 | ||
365 | ||
fb252f97 RS |
366 | (defun cust-print-circular (object) |
367 | "Printer for `prin1' and `princ' that handles circular structures. | |
ecb4184d | 368 | If OBJECT appears multiply, and has not yet been printed, |
fb252f97 | 369 | prefix with label; if it has been printed, use `#N#' instead. |
ecb4184d ER |
370 | Otherwise, print normally." |
371 | (let ((tag (assq object circle-table))) | |
372 | (if tag | |
373 | (let ((id (cdr tag))) | |
374 | (if (> id 0) | |
375 | (progn | |
376 | ;; Already printed, so just print id. | |
fb252f97 RS |
377 | (cust-print-internal-princ "#") |
378 | (cust-print-internal-princ id) | |
379 | (cust-print-internal-princ "#")) | |
ecb4184d ER |
380 | ;; Not printed yet, so label with id and print object. |
381 | (setcdr tag (- id)) ; mark it as printed | |
fb252f97 RS |
382 | (cust-print-internal-princ "#") |
383 | (cust-print-internal-princ (- id)) | |
384 | (cust-print-internal-princ "=") | |
385 | (cust-print-low-level-prin object) | |
ecb4184d ER |
386 | )) |
387 | ;; Not repeated in structure. | |
fb252f97 | 388 | (cust-print-low-level-prin object)))) |
ecb4184d ER |
389 | |
390 | ||
391 | ;;================================================ | |
392 | ;; List and vector processing for print functions. | |
393 | ||
fb252f97 RS |
394 | ;; Print a list using print-length, print-level, and print-circle. |
395 | (defun cust-print-list (list) | |
92ad69b6 | 396 | (if (= circle-level 0) |
fb252f97 | 397 | (cust-print-internal-princ "#") |
92ad69b6 | 398 | (let ((circle-level (1- circle-level))) |
fb252f97 | 399 | (cust-print-internal-princ "(") |
ecb4184d ER |
400 | (let ((length (or print-length 0))) |
401 | ||
402 | ;; Print the first element always (even if length = 0). | |
fb252f97 | 403 | (cust-print-prin (car list)) |
ecb4184d | 404 | (setq list (cdr list)) |
fb252f97 | 405 | (if list (cust-print-internal-princ " ")) |
ecb4184d ER |
406 | (setq length (1- length)) |
407 | ||
408 | ;; Print the rest of the elements. | |
409 | (while (and list (/= 0 length)) | |
410 | (if (and (listp list) | |
411 | (not (assq list circle-table))) | |
412 | (progn | |
fb252f97 | 413 | (cust-print-prin (car list)) |
ecb4184d ER |
414 | (setq list (cdr list))) |
415 | ||
416 | ;; cdr is not a list, or it is in circle-table. | |
fb252f97 RS |
417 | (cust-print-internal-princ ". ") |
418 | (cust-print-prin list) | |
ecb4184d ER |
419 | (setq list nil)) |
420 | ||
421 | (setq length (1- length)) | |
fb252f97 | 422 | (if list (cust-print-internal-princ " "))) |
ecb4184d | 423 | |
fb252f97 RS |
424 | (if (and list (= length 0)) (cust-print-internal-princ "...")) |
425 | (cust-print-internal-princ ")")))) | |
ecb4184d ER |
426 | list) |
427 | ||
428 | ||
fb252f97 RS |
429 | ;; Print a vector according to print-length, print-level, and print-circle. |
430 | (defun cust-print-vector (vector) | |
92ad69b6 | 431 | (if (= circle-level 0) |
fb252f97 | 432 | (cust-print-internal-princ "#") |
92ad69b6 | 433 | (let ((circle-level (1- circle-level)) |
ecb4184d ER |
434 | (i 0) |
435 | (len (length vector))) | |
fb252f97 | 436 | (cust-print-internal-princ "[") |
ecb4184d ER |
437 | |
438 | (if print-length | |
439 | (setq len (min print-length len))) | |
440 | ;; Print the elements | |
441 | (while (< i len) | |
fb252f97 | 442 | (cust-print-prin (aref vector i)) |
ecb4184d | 443 | (setq i (1+ i)) |
fb252f97 | 444 | (if (< i (length vector)) (cust-print-internal-princ " "))) |
ecb4184d | 445 | |
fb252f97 RS |
446 | (if (< i (length vector)) (cust-print-internal-princ "...")) |
447 | (cust-print-internal-princ "]") | |
ecb4184d ER |
448 | )) |
449 | vector) | |
450 | ||
451 | ||
452 | ;;================================== | |
453 | ;; Circular structure preprocessing | |
454 | ||
fb252f97 | 455 | (defun cust-print-preprocess-circle-tree (object) |
ecb4184d ER |
456 | ;; Fill up the table. |
457 | (let (;; Table of tags for each object in an object to be printed. | |
458 | ;; A tag is of the form: | |
459 | ;; ( <object> <nil-t-or-id-number> ) | |
460 | ;; The id-number is generated after the entire table has been computed. | |
461 | ;; During walk through, the real circle-table lives in the cdr so we | |
462 | ;; can use setcdr to add new elements instead of having to setq the | |
463 | ;; variable sometimes (poor man's locf). | |
464 | (circle-table (list nil))) | |
fb252f97 | 465 | (cust-print-walk-circle-tree object) |
ecb4184d ER |
466 | |
467 | ;; Reverse table so it is in the order that the objects will be printed. | |
468 | ;; This pass could be avoided if we always added to the end of the | |
469 | ;; table with setcdr in walk-circle-tree. | |
470 | (setcdr circle-table (nreverse (cdr circle-table))) | |
471 | ||
472 | ;; Walk through the table, assigning id-numbers to those | |
473 | ;; objects which will be printed using #N= syntax. Delete those | |
474 | ;; objects which will be printed only once (to speed up assq later). | |
475 | (let ((rest circle-table) | |
476 | (id -1)) | |
477 | (while (cdr rest) | |
478 | (let ((tag (car (cdr rest)))) | |
479 | (cond ((cdr tag) | |
480 | (setcdr tag id) | |
481 | (setq id (1- id)) | |
482 | (setq rest (cdr rest))) | |
483 | ;; Else delete this object. | |
484 | (t (setcdr rest (cdr (cdr rest)))))) | |
485 | )) | |
486 | ;; Drop the car. | |
487 | (cdr circle-table) | |
488 | )) | |
489 | ||
490 | ||
491 | ||
fb252f97 | 492 | (defun cust-print-walk-circle-tree (object) |
ecb4184d ER |
493 | (let (read-equivalent-p tag) |
494 | (while object | |
495 | (setq read-equivalent-p (or (numberp object) (symbolp object)) | |
496 | tag (and (not read-equivalent-p) | |
497 | (assq object (cdr circle-table)))) | |
498 | (cond (tag | |
499 | ;; Seen this object already, so note that. | |
500 | (setcdr tag t)) | |
501 | ||
502 | ((not read-equivalent-p) | |
503 | ;; Add a tag for this object. | |
504 | (setcdr circle-table | |
505 | (cons (list object) | |
506 | (cdr circle-table))))) | |
507 | (setq object | |
508 | (cond | |
509 | (tag ;; No need to descend since we have already. | |
510 | nil) | |
511 | ||
512 | ((consp object) | |
513 | ;; Walk the car of the list recursively. | |
fb252f97 | 514 | (cust-print-walk-circle-tree (car object)) |
ecb4184d ER |
515 | ;; But walk the cdr with the above while loop |
516 | ;; to avoid problems with max-lisp-eval-depth. | |
517 | ;; And it should be faster than recursion. | |
518 | (cdr object)) | |
519 | ||
520 | ((vectorp object) | |
521 | ;; Walk the vector. | |
522 | (let ((i (length object)) | |
523 | (j 0)) | |
524 | (while (< j i) | |
fb252f97 | 525 | (cust-print-walk-circle-tree (aref object j)) |
ecb4184d ER |
526 | (setq j (1+ j)))))))))) |
527 | ||
528 | ||
529 | ||
530 | ;;======================================= | |
531 | ||
92ad69b6 RS |
532 | ;; Example. |
533 | ||
534 | ;;;; Create some circular structures. | |
535 | ;;(setq circ-sym (let ((x (make-symbol "FOO"))) (list x x))) | |
536 | ;;(setq circ-list (list 'a 'b (vector 1 2 3 4) 'd 'e 'f)) | |
537 | ;;(setcar (nthcdr 3 circ-list) circ-list) | |
538 | ;;(aset (nth 2 circ-list) 2 circ-list) | |
539 | ;;(setq dotted-circ-list (list 'a 'b 'c)) | |
540 | ;;(setcdr (cdr (cdr dotted-circ-list)) dotted-circ-list) | |
541 | ;;(setq circ-vector (vector 1 2 3 4 (list 'a 'b 'c 'd) 6 7)) | |
542 | ;;(aset circ-vector 5 (make-symbol "-gensym-")) | |
543 | ;;(setcar (cdr (aref circ-vector 4)) (aref circ-vector 5)) | |
544 | ||
545 | ;;(install-custom-print-funcs) | |
546 | ;;;; (setq print-circle t) | |
547 | ||
548 | ;;(let ((print-circle t)) | |
549 | ;; (or (equal (prin1-to-string circ-list) "#1=(a b [1 2 #1# 4] #1# e f)") | |
550 | ;; (error "circular object with array printing"))) | |
551 | ||
552 | ;;(let ((print-circle t)) | |
553 | ;; (or (equal (prin1-to-string dotted-circ-list) "#1=(a b c . #1#)") | |
554 | ;; (error "circular object with array printing"))) | |
555 | ||
556 | ;;(let* ((print-circle t) | |
557 | ;; (x (list 'p 'q)) | |
558 | ;; (y (list (list 'a 'b) x 'foo x))) | |
559 | ;; (setcdr (cdr (cdr (cdr y))) (cdr y)) | |
560 | ;; (or (equal (prin1-to-string y) "((a b) . #1=(#2=(p q) foo #2# . #1#))" | |
561 | ;; ) | |
562 | ;; (error "circular list example from CL manual"))) | |
563 | ||
564 | ;;;; There's no special handling of uninterned symbols in custom-print. | |
565 | ;;(let ((print-circle nil)) | |
566 | ;; (or (equal (prin1-to-string circ-sym) "(#:FOO #:FOO)") | |
567 | ;; (error "uninterned symbols in list"))) | |
568 | ;;(let ((print-circle t)) | |
569 | ;; (or (equal (prin1-to-string circ-sym) "(#1=FOO #1#)") | |
570 | ;; (error "circular uninterned symbols in list"))) | |
571 | ;;(uninstall-custom-print-funcs) | |
ecb4184d | 572 | |
fd7fa35a | 573 | ;;; cust-print.el ends here |