3 ;;; Various handy utilities
5 ;;; (c) 2009 Straylight/Edgeware
8 ;;;----- Licensing notice ---------------------------------------------------
10 ;;; This file is part of the Sensble Object Design, an object system for C.
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.
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.
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.
26 (cl:defpackage #:sod-utilities
29 ;; MOP from somewhere.
31 #+(or cmu clisp) #:mop
34 (cl:in-package #:sod-utilities)
36 ;;;--------------------------------------------------------------------------
39 (export 'with-gensyms)
40 (defmacro with-gensyms ((&rest binds) &body body)
41 "Evaluate BODY with variables bound to fresh symbols.
43 The BINDS are a list of entries (VAR [NAME]), and a singleton list can be
44 replaced by just a symbol; each VAR is bound to a fresh symbol generated
45 by (gensym NAME), where NAME defaults to the symbol-name of VAR."
46 `(let (,@(mapcar (lambda (bind)
47 (multiple-value-bind (var name)
49 (values bind (concatenate 'string
50 (symbol-name bind) "-"))
53 (name (concatenate 'string
54 (symbol-name var) "-")))
57 `(,var (gensym ,name))))
61 (eval-when (:compile-toplevel :load-toplevel :execute)
62 (defun strip-quote (form)
63 "If FORM looks like (quote FOO) for self-evaluating FOO, return FOO.
65 If FORM is a symbol whose constant value is `nil' then return `nil'.
66 Otherwise return FORM unchanged. This makes it easier to inspect constant
67 things. This is a utility for `once-only'."
69 (cond ((and (consp form)
70 (eq (car form) 'quote)
73 (let ((body (cadr form)))
74 (if (or (not (or (consp body) (symbolp body)))
75 (member body '(t nil))
79 ((and (symbolp form) (boundp form) (null (symbol-value form)))
85 (defmacro once-only (binds &body body)
86 "Macro helper for preventing repeated evaluation.
88 The syntax is actually hairier than shown:
90 once-only ( [[ :environment ENV ]] { VAR | (VAR [VALUE-FORM]) }* )
93 So, the BINDS are a list of entries (VAR [VALUE-FORM]); a singleton list
94 can be replaced by just a symbol VAR, and the VALUE-FORM defaults to VAR.
95 But before them you can have keyword arguments. Only one is defined so
96 far. See below for the crazy things that does.
98 The result of evaluating a ONCE-ONLY form is a form with the structure
100 (let ((#:GS1 VALUE-FORM1)
105 where STUFF is the value of the BODY forms, as an implicit progn, in an
106 environment with the VARs bound to the corresponding gensyms.
108 As additional magic, if any of the VALUE-FORMs is actually constant (as
109 determined by inspection, and aided by `constantp' if an :environment is
110 supplied, then no gensym is constructed for it, and the VAR is bound
111 directly to the constant form. Moreover, if the constant form looks like
112 (quote FOO) for a self-evaluating FOO then the outer layer of quoting is
115 ;; We need an extra layer of gensyms in our expansion: we'll want the
116 ;; expansion to examine the various VALUE-FORMs to find out whether they're
117 ;; constant without evaluating them repeatedly. This also helps with
118 ;; another problem: we explicitly encourage the rebinding of a VAR
119 ;; (probably a macro argument) to a gensym which will be bound to the value
120 ;; of the form previously held in VAR itself -- so the gensym and value
121 ;; form must exist at the same time and we need two distinct variables.
123 (with-gensyms ((envvar "ENV-") lets sym (bodyfunc "BODY-"))
126 ;; First things first: let's pick up the keywords.
128 (unless (and binds (keywordp (car binds)))
131 (:environment (setf env (pop binds)))))
133 ;; Now we'll investigate the bindings. Turn each one into a list (VAR
134 ;; VALUE-FORM TEMP) where TEMP is an appropriate gensym -- see the note
136 (let ((canon (mapcar (lambda (bind)
137 (multiple-value-bind (var form)
141 (var &optional (form var)) bind
144 (gensym (format nil "T-~A-"
145 (symbol-name var))))))
148 `(let* (,@(and env `((,envvar ,env)))
150 ,@(mapcar (lambda (bind)
151 (destructuring-bind (var form temp) bind
152 (declare (ignore var))
155 ,@(mapcar (lambda (bind)
156 (destructuring-bind (var form temp) bind
157 (declare (ignore form))
159 (cond ((constantp ,temp
160 ,@(and env `(,envvar)))
166 ,(concatenate 'string
169 (push (list ,sym ,temp) ,lets)
172 (flet ((,bodyfunc () ,@body))
174 `(let (,@(nreverse ,lets)) ,(,bodyfunc))
178 (defun parse-body (body)
179 "Parse the BODY into a docstring, declarations and the body forms.
181 These are returned as three lists, so that they can be spliced into a
182 macro expansion easily. The declarations are consolidated into a single
187 (cond ((null body) (return))
188 ((and (consp (car body)) (eq (caar body) 'declare))
189 (setf decls (append decls (cdr (pop body)))))
190 ((and (stringp (car body)) (not doc) (cdr body))
191 (setf doc (pop body)))
193 (values (and doc (list doc))
194 (and decls (list (cons 'declare decls)))
197 ;;;--------------------------------------------------------------------------
201 (defstruct (loc (:predicate locp) (:constructor make-loc (reader writer)))
202 "Locative data type. See `locf' and `ref'."
203 (reader nil :type function)
204 (writer nil :type function))
207 (defmacro locf (place &environment env)
208 "Slightly cheesy locatives.
210 (locf PLACE) returns an object which, using the `ref' function, can be
211 used to read or set the value of PLACE. It's cheesy because it uses
212 closures rather than actually taking the address of something. Also,
213 unlike Zetalisp, we don't overload `car' to do our dirty work."
215 (valtmps valforms newtmps setform getform)
216 (get-setf-expansion place env)
217 `(let* (,@(mapcar #'list valtmps valforms))
218 (make-loc (lambda () ,getform)
219 (lambda (,@newtmps) ,setform)))))
222 (declaim (inline ref (setf ref)))
224 "Fetch the value referred to by a locative."
225 (funcall (loc-reader loc)))
226 (defun (setf ref) (new loc)
227 "Store a new value in the place referred to by a locative."
228 (funcall (loc-writer loc) new))
230 (export 'with-locatives)
231 (defmacro with-locatives (locs &body body)
232 "Evaluate BODY with implicit locatives.
234 LOCS is a list of items of the form (SYM [LOC-EXPR]), where SYM is a
235 symbol and LOC-EXPR evaluates to a locative. If LOC-EXPR is omitted, it
236 defaults to SYM. As an abbreviation for a common case, LOCS may be a
237 symbol instead of a list.
239 The BODY is evaluated in an environment where each SYM is a symbol macro
240 which expands to (ref LOC-EXPR) -- or, in fact, something similar which
241 doesn't break if LOC-EXPR has side-effects. Thus, references, including
242 `setf' forms, fetch or modify the thing referred to by the LOC-EXPR.
243 Useful for covering over where something uses a locative."
244 (setf locs (mapcar (lambda (item)
245 (cond ((atom item) (list item item))
246 ((null (cdr item)) (list (car item) (car item)))
248 (if (listp locs) locs (list locs))))
249 (let ((tt (mapcar (lambda (l) (declare (ignore l)) (gensym)) locs))
250 (ll (mapcar #'cadr locs))
251 (ss (mapcar #'car locs)))
252 `(let (,@(mapcar (lambda (tmp loc) `(,tmp ,loc)) tt ll))
253 (symbol-macrolet (,@(mapcar (lambda (sym tmp)
254 `(,sym (ref ,tmp))) ss tt))
257 ;;;--------------------------------------------------------------------------
263 (defmacro aif (cond cons &optional (alt nil altp))
264 "If COND is not nil, evaluate CONS with `it' bound to the value of COND.
266 Otherwise, if given, evaluate ALT; `it' isn't bound in ALT."
268 `(if ,cond (let ((it ,cond)) ,cons) ,@(and altp `(,alt)))))
271 (defmacro awhen (cond &body body)
272 "If COND, evaluate BODY as a progn with `it' bound to the value of COND."
273 `(let ((it ,cond)) (when it ,@body)))
276 (defmacro acond (&body clauses &environment env)
277 "Like COND, but with `it' bound to the value of the condition.
279 Each of the CLAUSES has the form (CONDITION FORM*); if a CONDITION is
280 non-nil then evaluate the FORMs with `it' bound to the non-nil value, and
281 return the value of the last FORM; if there are no FORMs, then return `it'
282 itself. If the CONDITION is nil then continue with the next clause; if
283 all clauses evaluate to nil then the result is nil."
284 (labels ((walk (clauses)
287 (once-only (:environment env (cond (caar clauses)))
288 (if (and (constantp cond)
289 (if (and (consp cond) (eq (car cond) 'quote))
293 (declare (ignorable it))
299 (declare (ignorable it))
302 ,(walk (cdr clauses))))))))
305 (export '(acase aecase atypecase aetypecase))
306 (defmacro acase (value &body clauses)
307 `(let ((it ,value)) (case it ,@clauses)))
308 (defmacro aecase (value &body clauses)
309 `(let ((it ,value)) (ecase it ,@clauses)))
310 (defmacro atypecase (value &body clauses)
311 `(let ((it ,value)) (typecase it ,@clauses)))
312 (defmacro aetypecase (value &body clauses)
313 `(let ((it ,value)) (etypecase it ,@clauses)))
316 (defmacro asetf (&rest places-and-values &environment env)
317 "Anaphoric update of places.
319 The PLACES-AND-VALUES are alternating PLACEs and VALUEs. Each VALUE is
320 evaluated with IT bound to the current value stored in the corresponding
322 `(progn ,@(loop for (place value) on places-and-values by #'cddr
323 collect (multiple-value-bind
324 (temps inits newtemps setform getform)
325 (get-setf-expansion place env)
326 `(let* (,@(mapcar #'list temps inits)
328 (multiple-value-bind ,newtemps ,value
331 ;;;--------------------------------------------------------------------------
332 ;;; MOP hacks (not terribly demanding).
334 (export 'instance-initargs)
335 (defgeneric instance-initargs (instance)
337 "Return a plausble list of initargs for INSTANCE.
339 The idea is that you can make a copy of INSTANCE by invoking
341 (apply #'make-instance (class-of INSTANCE)
342 (instance-initargs INSTANCE))
344 The default implementation works by inspecting the slot definitions and
345 extracting suitable initargs, so this will only succeed if enough slots
346 actually have initargs specified that `initialize-instance' can fill in
349 The list returned is freshly consed, and you can destroy it if you like.")
350 (:method ((instance standard-object))
351 (mapcan (lambda (slot)
352 (aif (slot-definition-initargs slot)
354 (slot-value instance (slot-definition-name slot)))
356 (class-slots (class-of instance)))))
358 (export '(copy-instance copy-instance-using-class))
359 (defgeneric copy-instance-using-class (class instance &rest initargs)
361 "Metaobject protocol hook for `copy-instance'.")
362 (:method ((class standard-class) instance &rest initargs)
363 (let ((copy (allocate-instance class)))
364 (dolist (slot (class-slots class))
365 (let ((name (slot-definition-name slot)))
366 (when (slot-boundp instance name)
367 (setf (slot-value copy name) (slot-value instance name)))))
368 (apply #'shared-initialize copy nil initargs))))
369 (defun copy-instance (object &rest initargs)
370 "Construct and return a copy of OBJECT.
372 The new object has the same class as OBJECT, and the same slot values
373 except where overridden by INITARGS."
374 (apply #'copy-instance-using-class (class-of object) object initargs))
376 (export '(generic-function-methods method-specializers
377 eql-specializer eql-specializer-object))
379 ;;;--------------------------------------------------------------------------
382 (export 'make-list-builder)
383 (defun make-list-builder (&optional initial)
384 "Return a simple list builder."
386 ;; The `builder' is just a cons cell whose cdr will be the list that's
387 ;; wanted. Effectively, then, we have a list that's one item longer than
388 ;; we actually want. The car of this extra initial cons cell is always the
389 ;; last cons in the list -- which is now well defined because there's
390 ;; always at least one.
392 (let ((builder (cons nil initial)))
393 (setf (car builder) (last builder))
397 (defun lbuild-add (builder item)
398 "Add an ITEM to the end of a list BUILDER."
399 (let ((new (cons item nil)))
400 (setf (cdar builder) new
404 (export 'lbuild-add-list)
405 (defun lbuild-add-list (builder list)
406 "Add a LIST to the end of a list BUILDER. The LIST will be clobbered."
408 (setf (cdar builder) list
409 (car builder) (last list)))
412 (export 'lbuild-list)
413 (defun lbuild-list (builder)
414 "Return the constructed list."
418 (defun mappend (function list &rest more-lists)
419 "Like a nondestructive MAPCAN.
421 Map FUNCTION over the the corresponding elements of LIST and MORE-LISTS,
422 and return the result of appending all of the resulting lists."
423 (reduce #'append (apply #'mapcar function list more-lists) :from-end t))
425 (export '(inconsistent-merge-error merge-error-candidates))
426 (define-condition inconsistent-merge-error (error)
427 ((candidates :initarg :candidates
428 :reader merge-error-candidates))
430 "Reports an inconsistency in the arguments passed to MERGE-LISTS.")
431 (:report (lambda (condition stream)
432 (format stream "Merge inconsistency: failed to decide among ~A."
433 (merge-error-candidates condition)))))
435 (export 'merge-lists)
436 (defun merge-lists (lists &key pick (test #'eql))
437 "Return a merge of the given LISTS.
439 The resulting LIST contains the items of the given lists, with duplicates
440 removed. The order of the resulting list is consistent with the orders of
441 the input LISTS in the sense that if A precedes B in some input list then
442 A will also precede B in the output list. If the lists aren't consistent
443 (e.g., some list contains A followed by B, and another contains B followed
444 by A) then an error of type `inconsistent-merge-error' is signalled.
446 Item equality is determined by TEST.
448 If there is an ambiguity at any point -- i.e., a choice between two or
449 more possible next items to emit -- then PICK is called to arbitrate.
450 PICK is called with two arguments: the list of candidate next items, and
451 the current output list. It should return one of the candidate items. If
452 PICK is omitted then an arbitrary choice is made.
454 The primary use of this function is in computing class precedence lists.
455 By building the input lists and selecting the PICK function appropriately,
456 a variety of different CPL algorithms can be implemented."
458 (do* ((lb (make-list-builder)))
459 ((null lists) (lbuild-list lb))
461 ;; The candidate items are the ones at the front of the input lists.
462 ;; Gather them up, removing duplicates. If a candidate is somewhere in
463 ;; one of the other lists other than at the front then we reject it. If
464 ;; we've just rejected everything, then we can make no more progress and
465 ;; the input lists were inconsistent.
466 (let* ((candidates (delete-duplicates (mapcar #'car lists) :test test))
467 (leasts (remove-if (lambda (item)
469 (member item (cdr list) :test test))
472 (winner (cond ((null leasts)
473 (error 'inconsistent-merge-error
474 :candidates candidates))
478 (funcall pick leasts (lbuild-list lb)))
481 ;; Check that the PICK function isn't conning us.
482 (assert (member winner leasts :test test))
484 ;; Update the output list and remove the winning item from the input
485 ;; lists. We know that it must be at the front of each input list
486 ;; containing it. At this point, we discard input lists entirely when
487 ;; they run out of entries. The loop ends when there are no more input
488 ;; lists left, i.e., when we've munched all of the input items.
489 (lbuild-add lb winner)
490 (setf lists (delete nil (mapcar (lambda (list)
491 (if (funcall test winner (car list))
497 (defmacro categorize ((itemvar items &key bind) categories &body body)
498 "Categorize ITEMS into lists and invoke BODY.
500 The ITEMVAR is a symbol; as the macro iterates over the ITEMS, ITEMVAR
501 will contain the current item. The BIND argument is a list of LET*-like
502 clauses. The CATEGORIES are a list of clauses of the form (SYMBOL
505 The behaviour of the macro is as follows. ITEMVAR is assigned (not
506 bound), in turn, each item in the list ITEMS. The PREDICATEs in the
507 CATEGORIES list are evaluated in turn, in an environment containing
508 ITEMVAR and the BINDings, until one of them evaluates to a non-nil value.
509 At this point, the item is assigned to the category named by the
510 corresponding SYMBOL. If none of the PREDICATEs returns non-nil then an
511 error is signalled; a PREDICATE consisting only of T will (of course)
512 match anything; it is detected specially so as to avoid compiler warnings.
514 Once all of the ITEMS have been categorized in this fashion, the BODY is
515 evaluated as an implicit PROGN. For each SYMBOL naming a category, a
516 variable named after that symbol will be bound in the BODY's environment
517 to a list of the items in that category, in the same order in which they
518 were found in the list ITEMS. The final values of the macro are the final
521 (let* ((cat-names (mapcar #'car categories))
522 (cat-match-forms (mapcar #'cadr categories))
523 (cat-vars (mapcar (lambda (name) (gensym (concatenate 'string
524 (symbol-name name) "-")))
526 (items-var (gensym "ITEMS-")))
527 `(let ((,items-var ,items)
528 ,@(mapcar (lambda (cat-var) (list cat-var nil)) cat-vars))
529 (dolist (,itemvar ,items-var)
531 (cond ,@(mapcar (lambda (cat-match-form cat-var)
533 (push ,itemvar ,cat-var)))
534 cat-match-forms cat-vars)
535 ,@(and (not (member t cat-match-forms))
536 `((t (error "Failed to categorize ~A" ,itemvar)))))))
537 (let ,(mapcar (lambda (name var)
538 `(,name (nreverse ,var)))
542 ;;;--------------------------------------------------------------------------
543 ;;; Strings and characters.
545 (export 'frob-identifier)
546 (defun frob-identifier (string &key (swap-case t) (swap-hyphen t))
547 "Twiddles the case of STRING.
549 If all the letters in STRING are uppercase, and SWAP-CASE is true, then
550 switch them to lowercase; if they're all lowercase then switch them to
551 uppercase. If there's a mix then leave them all alone. At the same time,
552 if there are underscores but no hyphens, and SWAP-HYPHEN is true, then
553 switch them to hyphens, if there are hyphens and no underscores, switch
554 them underscores, and if there are both then leave them alone.
556 This is an invertible transformation, which turns vaguely plausible Lisp
557 names into vaguely plausible C names and vice versa. Lisp names with
558 `funny characters' like stars and percent signs won't be any use, of
561 ;; Work out what kind of a job we've got to do. Gather flags: bit 0 means
562 ;; there are upper-case letters; bit 1 means there are lower-case letters;
563 ;; bit 2 means there are hyphens; bit 3 means there are underscores.
565 ;; Consequently, (logxor flags (ash flags 1)) is interesting: bit 1 is set
566 ;; if we have to frob case; bit 3 is set if we have to swap hyphens and
567 ;; underscores. So use this to select functions which do bits of the
568 ;; mapping, and then compose them together.
569 (let* ((flags (reduce (lambda (state ch)
571 (cond ((upper-case-p ch) 1)
572 ((lower-case-p ch) 2)
578 (mask (logxor flags (ash flags 1)))
579 (letter (cond ((or (not swap-case) (not (logbitp 1 mask)))
583 (and (alpha-char-p ch) (char-downcase ch))))
586 (and (alpha-char-p ch) (char-upcase ch))))))
587 (uscore-hyphen (cond ((or (not (logbitp 3 mask)) (not swap-hyphen))
590 (lambda (ch) (and (char= ch #\-) #\_)))
592 (lambda (ch) (and (char= ch #\_) #\-))))))
594 (if (logbitp 3 (logior mask (ash mask 2)))
595 (map 'string (lambda (ch)
596 (or (funcall letter ch)
597 (funcall uscore-hyphen ch)
602 (export 'whitespace-char-p)
603 (declaim (inline whitespace-char-p))
604 (defun whitespace-char-p (char)
605 "Returns whether CHAR is a whitespace character.
607 Whitespaceness is determined relative to the compile-time readtable, which
608 is probably good enough for most purposes."
610 (#.(loop for i below char-code-limit
611 for ch = (code-char i)
612 unless (with-input-from-string (in (string ch))
613 (peek-char t in nil))
617 (export 'update-position)
618 (declaim (inline update-position))
619 (defun update-position (char line column)
620 "Updates LINE and COLUMN appropriately for having read the character CHAR.
622 Returns the new LINE and COLUMN numbers."
624 ((#\newline #\vt #\page)
625 (values (1+ line) 0))
627 (values line (logandc2 (+ column 8) 7)))
629 (values line (1+ column)))))
631 (export 'backtrack-position)
632 (declaim (inline backtrack-position))
633 (defun backtrack-position (char line column)
634 "Updates LINE and COLUMN appropriately for having unread CHAR.
636 Well, actually an approximation for it; it will likely be wrong if the
637 last character was a tab. But when the character is read again, it will
640 ;; This isn't perfect: if the character doesn't actually match what was
641 ;; really read then it might not actually be possible: for example, if we
642 ;; push back a newline while in the middle of a line, or a tab while not at
643 ;; a tab stop. In that case, we'll just lose, but hopefully not too badly.
646 ;; In the absence of better ideas, I'll set the column number to zero.
647 ;; This is almost certainly wrong, but with a little luck nobody will ask
648 ;; and it'll be all right soon.
649 ((#\newline #\vt #\page) (values (1- line) 0))
651 ;; Winding back a single space is sufficient. If the position is
652 ;; currently on a tab stop then it'll advance back here next time. If
653 ;; not, we're going to lose anyway because the previous character
654 ;; certainly couldn't have been a tab.
655 (#\tab (values line (1- column)))
657 ;; Anything else: just decrement the column and cross fingers.
658 (t (values line (1- column)))))
660 ;;;--------------------------------------------------------------------------
664 (defun compose (function &rest more-functions)
665 "Composition of functions. Functions are applied left-to-right.
667 This is the reverse order of the usual mathematical notation, but I find
668 it easier to read. It's also slightly easier to work with in programs.
669 That is, (compose F1 F2 ... Fn) is what a category theorist might write as
670 F1 ; F2 ; ... ; Fn, rather than F1 o F2 o ... o Fn."
672 (labels ((compose1 (func-a func-b)
674 (multiple-value-call func-b (apply func-a args)))))
675 (reduce #'compose1 more-functions :initial-value function)))
677 ;;;--------------------------------------------------------------------------
680 (export 'symbolicate)
681 (defun symbolicate (&rest symbols)
682 "Return a symbol named after the concatenation of the names of the SYMBOLS.
684 The symbol is interned in the current `*package*'. Trad."
685 (intern (apply #'concatenate 'string (mapcar #'symbol-name symbols))))
687 ;;;--------------------------------------------------------------------------
690 (export 'maybe-print-unreadable-object)
691 (defmacro maybe-print-unreadable-object
692 ((object stream &rest args) &body body)
693 "Print helper for usually-unreadable objects.
695 If `*print-escape*' is set then print OBJECT unreadably using BODY.
696 Otherwise just print using BODY."
697 (with-gensyms (print)
698 `(flet ((,print () ,@body))
700 (print-unreadable-object (,object ,stream ,@args)
704 ;;;--------------------------------------------------------------------------
705 ;;; Iteration macros.
708 (defmacro dosequence ((var seq &key (start 0) (end nil) indexvar)
711 "Macro for iterating over general sequences.
713 Iterates over a (sub)sequence SEQ, delimited by START and END (which are
714 evaluated). For each item of SEQ, BODY is invoked with VAR bound to the
715 item, and INDEXVAR (if requested) bound to the item's index. (Note that
716 this is different from most iteration constructs in Common Lisp, which
717 work by mutating the variable.)
719 The loop is surrounded by an anonymous BLOCK and the loop body forms an
720 implicit TAGBODY, as is usual. There is no result-form, however."
722 (once-only (:environment env seq start end)
723 (with-gensyms ((ivar "INDEX-") (endvar "END-") (bodyfunc "BODY-"))
725 (flet ((loopguts (indexp listp endvar)
726 ;; Build a DO-loop to do what we want.
728 (end-condition (if endvar
734 (body-call `(,bodyfunc ,item)))
736 (push `(,seq (nthcdr ,start ,seq) (cdr ,seq))
739 (push `(,ivar ,start (1+ ,ivar)) do-vars))
741 (setf body-call (append body-call (list ivar))))
742 `(do ,do-vars (,end-condition) ,body-call))))
745 (flet ((,bodyfunc (,var ,@(and indexvar `(,indexvar)))
749 (let ((,endvar (or ,end (length ,seq))))
750 ,(loopguts t nil endvar)))
754 ,(loopguts indexvar t nil))))))))))
756 ;;;--------------------------------------------------------------------------
757 ;;; Structure accessor hacks.
759 (export 'define-access-wrapper)
760 (defmacro define-access-wrapper (from to &key read-only)
761 "Make (FROM THING) work like (TO THING).
763 If not READ-ONLY, then also make (setf (FROM THING) VALUE) work like
764 (setf (TO THING) VALUE).
766 This is mostly useful for structure slot accessors where the slot has to
767 be given an unpleasant name to avoid it being an external symbol."
769 (declaim (inline ,from ,@(and (not read-only) `((setf ,from)))))
770 (defun ,from (object)
772 ,@(and (not read-only)
773 `((defun (setf ,from) (value object)
774 (setf (,to object) value))))))
776 ;;;--------------------------------------------------------------------------
779 (export 'default-slot)
780 (defmacro default-slot ((instance slot &optional (slot-names t))
783 "If INSTANCE's slot named SLOT is unbound, set it to VALUE.
785 Only set SLOT if it's listed in SLOT-NAMES, or SLOT-NAMES is `t' (i.e., we
786 obey the `shared-initialize' protocol). SLOT-NAMES defaults to `t', so
787 you can use it in `initialize-instance' or similar without ill effects.
788 Both INSTANCE and SLOT are evaluated; VALUE is an implicit progn and only
789 evaluated if it's needed."
791 (once-only (:environment env instance slot slot-names)
792 `(when ,(if (eq slot-names t)
793 `(not (slot-boundp ,instance ,slot))
794 `(and (not (slot-boundp ,instance ,slot))
795 (or (eq ,slot-names t)
796 (member ,slot ,slot-names))))
797 (setf (slot-value ,instance ,slot)
800 (export 'define-on-demand-slot)
801 (defmacro define-on-demand-slot (class slot (instance) &body body)
802 "Defines a slot which computes its initial value on demand.
804 Sets up the named SLOT of CLASS to establish its value as the implicit
805 progn BODY, by defining an appropriate method on `slot-unbound'."
806 (with-gensyms (classvar slotvar)
807 `(defmethod slot-unbound
808 (,classvar (,instance ,class) (,slotvar (eql ',slot)))
809 (declare (ignore ,classvar))
810 (setf (slot-value ,instance ',slot) (progn ,@body)))))
812 ;;;----- That's all, folks --------------------------------------------------