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6 ;;;; to the software are in the public domain and are provided with
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12 ;;;; Copyright (c) 1985, 1986, 1987, 1988, 1989, 1990 Xerox Corporation.
13 ;;;; All rights reserved.
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16 ;;;; upon this software are permitted. Any distribution of this software or
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26 (defmacro define-method-combination (&whole form &rest args)
27 (declare (ignore args))
29 (with-single-package-locked-error
30 (:symbol ',(second form) "defining ~A as a method combination"))
33 (expand-long-defcombin form)
34 (expand-short-defcombin form))))
36 ;;;; standard method combination
38 ;;; The STANDARD method combination type is implemented directly by
39 ;;; the class STANDARD-METHOD-COMBINATION. The method on
40 ;;; COMPUTE-EFFECTIVE-METHOD does standard method combination directly
41 ;;; and is defined by hand in the file combin.lisp. The method for
42 ;;; FIND-METHOD-COMBINATION must appear in this file for bootstrapping
44 (defmethod find-method-combination ((generic-function generic-function)
45 (type (eql 'standard))
48 (method-combination-error
49 "The method combination type STANDARD accepts no options."))
50 *standard-method-combination*)
52 ;;;; short method combinations
54 ;;;; Short method combinations all follow the same rule for computing the
55 ;;;; effective method. So, we just implement that rule once. Each short
56 ;;;; method combination object just reads the parameters out of the object
57 ;;;; and runs the same rule.
59 (defclass short-method-combination (standard-method-combination)
61 :reader short-combination-operator
63 (identity-with-one-argument
64 :reader short-combination-identity-with-one-argument
65 :initarg :identity-with-one-argument))
66 (:predicate-name short-method-combination-p))
68 (defun expand-short-defcombin (whole)
69 (let* ((type (cadr whole))
71 (getf (cddr whole) :documentation ""))
72 (identity-with-one-arg
73 (getf (cddr whole) :identity-with-one-argument nil))
75 (getf (cddr whole) :operator type)))
76 `(load-short-defcombin
77 ',type ',operator ',identity-with-one-arg ',documentation)))
79 (defun load-short-defcombin (type operator ioa doc)
80 (let* ((pathname *load-pathname*)
82 (list (find-class 'generic-function)
83 (intern-eql-specializer type)
86 (get-method #'find-method-combination () specializers nil))
89 (make-instance 'standard-method
91 :specializers specializers
92 :lambda-list '(generic-function type options)
93 :function (lambda (args nms &rest cm-args)
94 (declare (ignore nms cm-args))
96 (lambda (gf type options)
98 (short-combine-methods
99 type options operator ioa new-method doc))
101 :definition-source `((define-method-combination ,type) ,pathname)))
103 (remove-method #'find-method-combination old-method))
104 (add-method #'find-method-combination new-method)
105 (setf (random-documentation type 'method-combination) doc)
108 (defun short-combine-methods (type options operator ioa method doc)
109 (cond ((null options) (setq options '(:most-specific-first)))
110 ((equal options '(:most-specific-first)))
111 ((equal options '(:most-specific-last)))
113 (method-combination-error
114 "Illegal options to a short method combination type.~%~
115 The method combination type ~S accepts one option which~%~
116 must be either :MOST-SPECIFIC-FIRST or :MOST-SPECIFIC-LAST."
118 (make-instance 'short-method-combination
122 :identity-with-one-argument ioa
123 :definition-source method
126 (defmethod compute-effective-method ((generic-function generic-function)
127 (combin short-method-combination)
129 (let ((type (method-combination-type combin))
130 (operator (short-combination-operator combin))
131 (ioa (short-combination-identity-with-one-argument combin))
132 (order (car (method-combination-options combin)))
135 (flet ((invalid (gf combin m)
136 (if *in-precompute-effective-methods-p*
137 (return-from compute-effective-method
138 `(%invalid-qualifiers ',gf ',combin ',m))
139 (invalid-qualifiers gf combin m))))
140 (dolist (m applicable-methods)
141 (let ((qualifiers (method-qualifiers m)))
142 (cond ((null qualifiers) (invalid generic-function combin m))
143 ((cdr qualifiers) (invalid generic-function combin m))
144 ((eq (car qualifiers) :around)
146 ((eq (car qualifiers) type)
148 (t (invalid generic-function combin m))))))
149 (setq around (nreverse around))
151 (:most-specific-last) ; nothing to be done, already in correct order
152 (:most-specific-first
153 (setq primary (nreverse primary))))
155 (if (and (null (cdr primary))
157 `(call-method ,(car primary) ())
158 `(,operator ,@(mapcar (lambda (m) `(call-method ,m ()))
160 (cond ((null primary)
161 ;; As of sbcl-0.8.0.80 we don't seem to need to need
162 ;; to do anything messy like
163 ;; `(APPLY (FUNCTION (IF AROUND
164 ;; 'NO-PRIMARY-METHOD
165 ;; 'NO-APPLICABLE-METHOD)
166 ;; ',GENERIC-FUNCTION
168 ;; here because (for reasons I don't understand at the
169 ;; moment -- WHN) control will never reach here if there
170 ;; are no applicable methods, but instead end up
171 ;; in NO-APPLICABLE-METHODS first.
173 ;; FIXME: The way that we arrange for .ARGS. to be bound
174 ;; here seems weird. We rely on EXPAND-EFFECTIVE-METHOD-FUNCTION
175 ;; recognizing any form whose operator is %NO-PRIMARY-METHOD
176 ;; as magical, and carefully surrounding it with a
177 ;; LAMBDA form which binds .ARGS. But...
178 ;; 1. That seems fragile, because the magicalness of
179 ;; %NO-PRIMARY-METHOD forms is scattered around
180 ;; the system. So it could easily be broken by
181 ;; locally-plausible maintenance changes like,
182 ;; e.g., using the APPLY expression above.
183 ;; 2. That seems buggy w.r.t. to MOPpish tricks in
185 ;; (DEFMETHOD COMPUTE-EFFECTIVE-METHOD :AROUND (...)
186 ;; `(PROGN ,(CALL-NEXT-METHOD) (INCF *MY-CTR*)))
187 `(%no-primary-method ',generic-function .args.))
188 ((null around) main-method)
190 `(call-method ,(car around)
191 (,@(cdr around) (make-method ,main-method))))))))
193 (defmethod invalid-qualifiers ((gf generic-function)
194 (combin short-method-combination)
196 (let ((qualifiers (method-qualifiers method))
197 (type (method-combination-type combin)))
199 ((null qualifiers) "has no qualifiers")
200 ((cdr qualifiers) "has too many qualifiers")
201 (t (aver (and (neq (car qualifiers) type)
202 (neq (car qualifiers) :around)))
203 "has an invalid qualifier"))))
204 (invalid-method-error
206 "The method ~S on ~S ~A.~%~
207 The method combination type ~S was defined with the~%~
208 short form of DEFINE-METHOD-COMBINATION and so requires~%~
209 all methods have either the single qualifier ~S or the~%~
210 single qualifier :AROUND."
211 method gf why type type))))
213 ;;;; long method combinations
215 (defun expand-long-defcombin (form)
216 (let ((type (cadr form))
217 (lambda-list (caddr form))
218 (method-group-specifiers (cadddr form))
222 (when (and (consp (car body)) (eq (caar body) :arguments))
223 (setq args-option (cdr (pop body))))
224 (when (and (consp (car body)) (eq (caar body) :generic-function))
225 (setq gf-var (cadr (pop body))))
226 (multiple-value-bind (documentation function)
227 (make-long-method-combination-function
228 type lambda-list method-group-specifiers args-option gf-var
230 `(load-long-defcombin ',type ',documentation #',function
233 (defvar *long-method-combination-functions* (make-hash-table :test 'eq))
235 (defun load-long-defcombin (type doc function args-lambda-list)
237 (list (find-class 'generic-function)
238 (intern-eql-specializer type)
241 (get-method #'find-method-combination () specializers nil))
243 (make-instance 'standard-method
245 :specializers specializers
246 :lambda-list '(generic-function type options)
247 :function (lambda (args nms &rest cm-args)
248 (declare (ignore nms cm-args))
250 (lambda (generic-function type options)
251 (declare (ignore generic-function))
252 (make-instance 'long-method-combination
255 :args-lambda-list args-lambda-list
258 :definition-source `((define-method-combination ,type)
260 (setf (gethash type *long-method-combination-functions*) function)
261 (when old-method (remove-method #'find-method-combination old-method))
262 (add-method #'find-method-combination new-method)
263 (setf (random-documentation type 'method-combination) doc)
266 (defmethod compute-effective-method ((generic-function generic-function)
267 (combin long-method-combination)
269 (funcall (gethash (method-combination-type combin)
270 *long-method-combination-functions*)
275 (defun make-long-method-combination-function
276 (type ll method-group-specifiers args-option gf-var body)
277 (declare (ignore type))
278 (multiple-value-bind (real-body declarations documentation)
281 (wrap-method-group-specifier-bindings method-group-specifiers
285 (push `(,gf-var .generic-function.) (cadr wrapped-body)))
288 (setq wrapped-body (deal-with-args-option wrapped-body args-option)))
292 `(apply #'(lambda ,ll ,wrapped-body)
293 (method-combination-options .method-combination.))))
297 `(lambda (.generic-function. .method-combination. .applicable-methods.)
298 (declare (ignorable .generic-function.
299 .method-combination. .applicable-methods.))
300 (block .long-method-combination-function. ,wrapped-body))))))
302 (define-condition long-method-combination-error
303 (reference-condition simple-error)
306 :references (list '(:ansi-cl :macro define-method-combination))))
310 ;;; The semantics of long form method combination in the presence of
311 ;;; multiple methods with the same specializers in the same method
312 ;;; group are unclear by the spec: a portion of the standard implies
313 ;;; that an error should be signalled, and another is more lenient.
315 ;;; It is reasonable to allow a single method group of * to bypass all
316 ;;; rules, as this is explicitly stated in the standard.
318 (defun group-cond-clause (name tests specializer-cache star-only)
319 (let ((maybe-error-clause
321 `(setq ,specializer-cache .specializers.)
322 `(if (and (equal ,specializer-cache .specializers.)
323 (not (null .specializers.)))
324 (return-from .long-method-combination-function.
325 '(error 'long-method-combination-error
326 :format-control "More than one method of type ~S ~
327 with the same specializers."
328 :format-arguments (list ',name)))
329 (setq ,specializer-cache .specializers.)))))
332 (push .method. ,name))))
334 (defun wrap-method-group-specifier-bindings
335 (method-group-specifiers declarations real-body)
336 (let (names specializer-caches cond-clauses required-checks order-cleanups)
337 (let ((nspecifiers (length method-group-specifiers)))
338 (dolist (method-group-specifier method-group-specifiers)
339 (multiple-value-bind (name tests description order required)
340 (parse-method-group-specifier method-group-specifier)
341 (declare (ignore description))
342 (let ((specializer-cache (gensym)))
344 (push specializer-cache specializer-caches)
345 (push (group-cond-clause name tests specializer-cache
346 (and (eq (cadr method-group-specifier) '*)
350 (push `(when (null ,name)
351 (return-from .long-method-combination-function.
352 '(error 'long-method-combination-error
353 :format-control "No ~S methods."
354 :format-arguments (list ',name))))
356 (loop (unless (and (constantp order)
357 (neq order (setq order (eval order))))
359 (push (cond ((eq order :most-specific-first)
360 `(setq ,name (nreverse ,name)))
361 ((eq order :most-specific-last) ())
364 (:most-specific-first
365 (setq ,name (nreverse ,name)))
366 (:most-specific-last))))
368 `(let (,@(nreverse names) ,@(nreverse specializer-caches))
370 (dolist (.method. .applicable-methods.)
371 (let ((.qualifiers. (method-qualifiers .method.))
372 (.specializers. (method-specializers .method.)))
373 (declare (ignorable .qualifiers. .specializers.))
374 (cond ,@(nreverse cond-clauses))))
375 ,@(nreverse required-checks)
376 ,@(nreverse order-cleanups)
379 (defun parse-method-group-specifier (method-group-specifier)
380 ;;(declare (values name tests description order required))
381 (let* ((name (pop method-group-specifier))
387 (if (or (null method-group-specifier)
388 (memq (car method-group-specifier)
389 '(:description :order :required)))
390 (return-from collect-tests t)
391 (let ((pattern (pop method-group-specifier)))
392 (push pattern patterns)
393 (push (parse-qualifier-pattern name pattern)
395 (nreverse collect))))
398 (getf method-group-specifier :description
399 (make-default-method-group-description patterns))
400 (getf method-group-specifier :order :most-specific-first)
401 (getf method-group-specifier :required nil))))
403 (defun parse-qualifier-pattern (name pattern)
404 (cond ((eq pattern '()) `(null .qualifiers.))
406 ((symbolp pattern) `(,pattern .qualifiers.))
407 ((listp pattern) `(qualifier-check-runtime ',pattern .qualifiers.))
408 (t (error "In the method group specifier ~S,~%~
409 ~S isn't a valid qualifier pattern."
412 (defun qualifier-check-runtime (pattern qualifiers)
413 (loop (cond ((and (null pattern) (null qualifiers))
415 ((eq pattern '*) (return t))
416 ((and pattern qualifiers (eq (car pattern) (car qualifiers)))
421 (defun make-default-method-group-description (patterns)
424 "methods matching one of the patterns: ~{~S, ~} ~S"
425 (butlast patterns) (car (last patterns)))
427 "methods matching the pattern: ~S"
430 ;;; This baby is a complete mess. I can't believe we put it in this
431 ;;; way. No doubt this is a large part of what drives MLY crazy.
433 ;;; At runtime (when the effective-method is run), we bind an intercept
434 ;;; lambda-list to the arguments to the generic function.
436 ;;; At compute-effective-method time, the symbols in the :arguments
437 ;;; option are bound to the symbols in the intercept lambda list.
439 ;;; FIXME: in here we have not one but two mini-copies of a weird
440 ;;; hybrid of PARSE-LAMBDA-LIST and PARSE-DEFMACRO-LAMBDA-LIST.
441 (defun deal-with-args-option (wrapped-body args-lambda-list)
442 (let ((intercept-rebindings
444 (dolist (arg args-lambda-list (nreverse rebindings))
445 (unless (member arg lambda-list-keywords)
447 (symbol (push `(,arg ',arg) rebindings))
449 (unless (symbolp (car arg))
450 (error "invalid lambda-list specifier: ~S." arg))
451 (push `(,(car arg) ',(car arg)) rebindings))
452 (t (error "invalid lambda-list-specifier: ~S." arg)))))))
456 ;; Count the number of required and optional parameters in
457 ;; ARGS-LAMBDA-LIST into NREQ and NOPT, and set WHOLE to the
458 ;; name of a &WHOLE parameter, if any.
459 (when (member '&whole (rest args-lambda-list))
460 (error 'simple-program-error
461 :format-control "~@<The value of the :ARGUMENTS option of ~
462 DEFINE-METHOD-COMBINATION is~2I~_~S,~I~_but &WHOLE may ~
463 only appear first in the lambda list.~:>"
464 :format-arguments (list args-lambda-list)))
465 (loop with state = 'required
466 for arg in args-lambda-list do
467 (if (memq arg lambda-list-keywords)
470 (required (incf nreq))
471 (&optional (incf nopt))
472 (&whole (setq whole arg state 'required)))))
473 ;; This assumes that the head of WRAPPED-BODY is a let, and it
474 ;; injects let-bindings of the form (ARG 'SYM) for all variables
475 ;; of the argument-lambda-list; SYM is a gensym.
476 (aver (memq (first wrapped-body) '(let let*)))
477 (setf (second wrapped-body)
478 (append intercept-rebindings (second wrapped-body)))
479 ;; Be sure to fill out the args lambda list so that it can be too
480 ;; short if it wants to.
481 (unless (or (memq '&rest args-lambda-list)
482 (memq '&allow-other-keys args-lambda-list))
483 (let ((aux (memq '&aux args-lambda-list)))
484 (setq args-lambda-list
485 (append (ldiff args-lambda-list aux)
486 (if (memq '&key args-lambda-list)
490 ;; .GENERIC-FUNCTION. is bound to the generic function in the
491 ;; method combination function, and .GF-ARGS* is bound to the
492 ;; generic function arguments in effective method functions
493 ;; created for generic functions having a method combination that
496 ;; The DESTRUCTURING-BIND binds the parameters of the
497 ;; ARGS-LAMBDA-LIST to actual generic function arguments. Because
498 ;; ARGS-LAMBDA-LIST may be shorter or longer than the generic
499 ;; function's lambda list, which is only known at run time, this
500 ;; destructuring has to be done on a slighly modified list of
501 ;; actual arguments, from which values might be stripped or added.
503 ;; Using one of the variable names in the body inserts a symbol
504 ;; into the effective method, and running the effective method
505 ;; produces the value of actual argument that is bound to the
507 `(let ((inner-result. ,wrapped-body)
508 (gf-lambda-list (generic-function-lambda-list .generic-function.)))
509 `(destructuring-bind ,',args-lambda-list
510 (frob-combined-method-args
511 .gf-args. ',gf-lambda-list
513 ,,(when (memq '.ignore. args-lambda-list)
514 ''(declare (ignore .ignore.)))
515 ;; If there is a &WHOLE in the args-lambda-list, let
516 ;; it result in the actual arguments of the generic-function
517 ;; not the frobbed list.
519 ``(setq ,',whole .gf-args.))
522 ;;; Partition VALUES into three sections: required, optional, and the
523 ;;; rest, according to required, optional, and other parameters in
524 ;;; LAMBDA-LIST. Make the required and optional sections NREQ and
525 ;;; NOPT elements long by discarding values or adding NILs. Value is
526 ;;; the concatenated list of required and optional sections, and what
527 ;;; is left as rest from VALUES.
528 (defun frob-combined-method-args (values lambda-list nreq nopt)
529 (loop with section = 'required
530 for arg in lambda-list
531 if (memq arg lambda-list-keywords) do
533 (unless (eq section '&optional)
535 else if (eq section 'required)
537 and collect (pop values) into required
538 else if (eq section '&optional)
540 and collect (pop values) into optional
542 (flet ((frob (list n m)
543 (cond ((> n m) (butlast list (- n m)))
544 ((< n m) (nconc list (make-list (- m n))))
546 (return (nconc (frob required nr nreq)
547 (frob optional no nopt)