1;;;; This software is part of the SBCL system. See the README file for
2;;;; more information.
3
4;;;; This software is derived from software originally released by Xerox
5;;;; Corporation. Copyright and release statements follow. Later modifications
6;;;; to the software are in the public domain and are provided with
7;;;; absolutely no warranty. See the COPYING and CREDITS files for more
8;;;; information.
9
10;;;; copyright information from original PCL sources:
11;;;;
12;;;; Copyright (c) 1985, 1986, 1987, 1988, 1989, 1990 Xerox Corporation.
13;;;; All rights reserved.
14;;;;
15;;;; Use and copying of this software and preparation of derivative works based
16;;;; upon this software are permitted. Any distribution of this software or
17;;;; derivative works must comply with all applicable United States export
18;;;; control laws.
19;;;;
20;;;; This software is made available AS IS, and Xerox Corporation makes no
21;;;; warranty about the software, its performance or its conformity to any
22;;;; specification.
23
24(in-package "SB-PCL")
25
26;;; FIXME: according to ANSI 3.4.10 this is supposed to allow &WHOLE
27;;; in the long syntax. But it clearly does not, because if you write
28;;; (&WHOLE v) then you get (LAMBDA (&WHOLE V ...) ...) which is illegal
29;;;
30(defmacro define-method-combination (&whole form &rest args)
31  (declare (ignore args))
32  `(progn
33     (with-single-package-locked-error
34         (:symbol ',(second form) "defining ~A as a method combination"))
35     ,(if (and (cddr form)
36               (listp (caddr form)))
37          (expand-long-defcombin form)
38          (expand-short-defcombin form))))
39
40;;;; standard method combination
41
42;;; The STANDARD method combination type is implemented directly by
43;;; the class STANDARD-METHOD-COMBINATION. The method on
44;;; COMPUTE-EFFECTIVE-METHOD does standard method combination directly
45;;; and is defined by hand in the file combin.lisp. The method for
46;;; FIND-METHOD-COMBINATION must appear in this file for bootstrapping
47;;; reasons.
48(defmethod find-method-combination ((generic-function generic-function)
49                                    (type-name (eql 'standard))
50                                    options)
51  (when options
52    (method-combination-error
53      "STANDARD method combination accepts no options."))
54  *standard-method-combination*)
55
56;;;; short method combinations
57;;;;
58;;;; Short method combinations all follow the same rule for computing the
59;;;; effective method. So, we just implement that rule once. Each short
60;;;; method combination object just reads the parameters out of the object
61;;;; and runs the same rule.
62
63(defun expand-short-defcombin (whole)
64  (let* ((type-name (cadr whole))
65         (documentation
66           (getf (cddr whole) :documentation))
67         (identity-with-one-arg
68           (getf (cddr whole) :identity-with-one-argument nil))
69         (operator
70           (getf (cddr whole) :operator type-name)))
71    `(load-short-defcombin
72     ',type-name ',operator ',identity-with-one-arg ',documentation
73      (sb-c:source-location))))
74
75(defun load-short-defcombin (type-name operator ioa doc source-location)
76  (let* ((specializers
77           (list (find-class 'generic-function)
78                 (intern-eql-specializer type-name)
79                 *the-class-t*))
80         (old-method
81           (get-method #'find-method-combination () specializers nil))
82         (new-method nil))
83    (setq new-method
84          (make-instance 'standard-method
85            :qualifiers ()
86            :specializers specializers
87            :lambda-list '(generic-function type-name options)
88            :function (lambda (args nms &rest cm-args)
89                        (declare (ignore nms cm-args))
90                        (apply
91                         (lambda (gf type-name options)
92                           (declare (ignore gf))
93                           (short-combine-methods
94                            type-name options operator ioa new-method doc))
95                         args))
96            :definition-source source-location))
97    (when old-method
98      (remove-method #'find-method-combination old-method))
99    (add-method #'find-method-combination new-method)
100    (setf (random-documentation type-name 'method-combination) doc)
101    type-name))
102
103(defun short-combine-methods (type-name options operator ioa method doc)
104  (cond ((null options) (setq options '(:most-specific-first)))
105        ((equal options '(:most-specific-first)))
106        ((equal options '(:most-specific-last)))
107        (t
108         (method-combination-error
109          "Illegal options to a short method combination type.~%~
110           The method combination type ~S accepts one option which~%~
111           must be either :MOST-SPECIFIC-FIRST or :MOST-SPECIFIC-LAST."
112          type-name)))
113  (make-instance 'short-method-combination
114                 :type-name type-name
115                 :options options
116                 :operator operator
117                 :identity-with-one-argument ioa
118                 :definition-source method
119                 :documentation doc))
120
121(defmethod invalid-qualifiers ((gf generic-function)
122                               (combin short-method-combination)
123                               method)
124  (let* ((qualifiers (method-qualifiers method))
125         (qualifier (first qualifiers))
126         (type-name (method-combination-type-name combin))
127         (why (cond
128                ((null qualifiers)
129                 "has no qualifiers")
130                ((cdr qualifiers)
131                 "has too many qualifiers")
132                (t
133                 (aver (not (short-method-combination-qualifier-p
134                             type-name qualifier)))
135                 "has an invalid qualifier"))))
136    (invalid-method-error
137     method
138     "~@<The method ~S on ~S ~A.~
139      ~@:_~@:_~
140      The method combination type ~S was defined with the short form ~
141      of DEFINE-METHOD-COMBINATION and so requires all methods have ~
142      either ~{the single qualifier ~S~^ or ~}.~@:>"
143     method gf why type-name (short-method-combination-qualifiers type-name))))
144
145;;;; long method combinations
146
147(defun expand-long-defcombin (form)
148  (let ((type-name (cadr form))
149        (lambda-list (caddr form))
150        (method-group-specifiers (cadddr form))
151        (body (cddddr form))
152        (args-option ())
153        (gf-var nil))
154    (when (and (consp (car body)) (eq (caar body) :arguments))
155      (setq args-option (cdr (pop body))))
156    (when (and (consp (car body)) (eq (caar body) :generic-function))
157      (setq gf-var (cadr (pop body))))
158    (multiple-value-bind (documentation function)
159        (make-long-method-combination-function
160          type-name lambda-list method-group-specifiers args-option gf-var
161          body)
162      `(load-long-defcombin ',type-name ',documentation #',function
163                            ',args-option (sb-c:source-location)))))
164
165(defvar *long-method-combination-functions* (make-hash-table :test 'eq))
166
167(defun load-long-defcombin
168    (type-name doc function args-lambda-list source-location)
169  (let* ((specializers
170           (list (find-class 'generic-function)
171                 (intern-eql-specializer type-name)
172                 *the-class-t*))
173         (old-method
174           (get-method #'find-method-combination () specializers nil))
175         (new-method
176           (make-instance 'standard-method
177             :qualifiers ()
178             :specializers specializers
179             :lambda-list '(generic-function type-name options)
180             :function (lambda (args nms &rest cm-args)
181                         (declare (ignore nms cm-args))
182                         (apply
183                          (lambda (generic-function type-name options)
184                            (declare (ignore generic-function))
185                            (make-instance 'long-method-combination
186                                           :type-name type-name
187                                           :options options
188                                           :args-lambda-list args-lambda-list
189                                           :documentation doc))
190                          args))
191             :definition-source source-location)))
192    (setf (gethash type-name *long-method-combination-functions*) function)
193    (when old-method (remove-method #'find-method-combination old-method))
194    (add-method #'find-method-combination new-method)
195    (setf (random-documentation type-name 'method-combination) doc)
196    type-name))
197
198(defmethod compute-effective-method ((generic-function generic-function)
199                                     (combin long-method-combination)
200                                     applicable-methods)
201  (funcall (gethash (method-combination-type-name combin)
202                    *long-method-combination-functions*)
203           generic-function
204           combin
205           applicable-methods))
206
207(defun make-long-method-combination-function
208       (type-name ll method-group-specifiers args-option gf-var body)
209  (declare (ignore type-name))
210  (multiple-value-bind (real-body declarations documentation)
211      (parse-body body t)
212    (let ((wrapped-body
213            (wrap-method-group-specifier-bindings method-group-specifiers
214                                                  declarations
215                                                  real-body)))
216      (when gf-var
217        (push `(,gf-var .generic-function.) (cadr wrapped-body)))
218
219      (when args-option
220        (setq wrapped-body (deal-with-args-option wrapped-body args-option)))
221
222      (when ll
223        (setq wrapped-body
224              `(apply #'(lambda ,ll ,wrapped-body)
225                      (method-combination-options .method-combination.))))
226
227      (values
228        documentation
229        `(lambda (.generic-function. .method-combination. .applicable-methods.)
230           (declare (ignorable .generic-function.
231                     .method-combination. .applicable-methods.))
232           (block .long-method-combination-function. ,wrapped-body))))))
233
234(define-condition long-method-combination-error
235    (reference-condition simple-error)
236  ()
237  (:default-initargs
238   :references (list '(:ansi-cl :macro define-method-combination))))
239
240;;; NOTE:
241;;;
242;;; The semantics of long form method combination in the presence of
243;;; multiple methods with the same specializers in the same method
244;;; group are unclear by the spec: a portion of the standard implies
245;;; that an error should be signalled, and another is more lenient.
246;;;
247;;; It is reasonable to allow a single method group of * to bypass all
248;;; rules, as this is explicitly stated in the standard.
249
250(defun group-cond-clause (name tests specializer-cache star-only)
251  (let ((maybe-error-clause
252         (if star-only
253             `(setq ,specializer-cache .specializers.)
254             `(if (and (equal ,specializer-cache .specializers.)
255                       (not (null .specializers.)))
256                  (return-from .long-method-combination-function.
257                    '(error 'long-method-combination-error
258                      :format-control "More than one method of type ~S ~
259                                       with the same specializers."
260                      :format-arguments (list ',name)))
261                  (setq ,specializer-cache .specializers.)))))
262    `((or ,@tests)
263      ,maybe-error-clause
264      (push .method. ,name))))
265
266(defun wrap-method-group-specifier-bindings
267    (method-group-specifiers declarations real-body)
268  (let (names specializer-caches cond-clauses required-checks order-cleanups)
269    (let ((nspecifiers (length method-group-specifiers)))
270      (dolist (method-group-specifier method-group-specifiers
271               (push `(t (return-from .long-method-combination-function.
272                           `(invalid-method-error , .method.
273                             "~@<is applicable, but does not belong ~
274                              to any method group~@:>")))
275                     cond-clauses))
276        (multiple-value-bind (name tests description order required)
277            (parse-method-group-specifier method-group-specifier)
278          (declare (ignore description))
279          (let ((specializer-cache (gensym)))
280            (push name names)
281            (push specializer-cache specializer-caches)
282            (push (group-cond-clause name tests specializer-cache
283                                     (and (eq (cadr method-group-specifier) '*)
284                                          (= nspecifiers 1)))
285                  cond-clauses)
286            (when required
287              (push `(when (null ,name)
288                      (return-from .long-method-combination-function.
289                        '(error 'long-method-combination-error
290                          :format-control "No ~S methods."
291                          :format-arguments (list ',name))))
292                    required-checks))
293            (loop (unless (and (constantp order)
294                               (neq order (setq order
295                                                (constant-form-value order))))
296                    (return t)))
297            (push (cond ((eq order :most-specific-first)
298                         `(setq ,name (nreverse ,name)))
299                        ((eq order :most-specific-last) ())
300                        (t
301                         `(ecase ,order
302                           (:most-specific-first
303                            (setq ,name (nreverse ,name)))
304                           (:most-specific-last))))
305                  order-cleanups))))
306      `(let (,@(nreverse names) ,@(nreverse specializer-caches))
307        ,@declarations
308        (dolist (.method. .applicable-methods.)
309          (let ((.qualifiers. (method-qualifiers .method.))
310                (.specializers. (method-specializers .method.)))
311            (declare (ignorable .qualifiers. .specializers.))
312            (cond ,@(nreverse cond-clauses))))
313        ,@(nreverse required-checks)
314        ,@(nreverse order-cleanups)
315        ,@real-body))))
316
317(defun parse-method-group-specifier (method-group-specifier)
318  ;;(declare (values name tests description order required))
319  (let* ((name (pop method-group-specifier))
320         (patterns ())
321         (tests
322           (let (collect)
323             (block collect-tests
324               (loop
325                 (if (or (null method-group-specifier)
326                         (memq (car method-group-specifier)
327                               '(:description :order :required)))
328                     (return-from collect-tests t)
329                     (let ((pattern (pop method-group-specifier)))
330                       (push pattern patterns)
331                       (push (parse-qualifier-pattern name pattern)
332                             collect)))))
333             (nreverse collect))))
334    (values name
335            tests
336            (getf method-group-specifier :description
337                  (make-default-method-group-description patterns))
338            (getf method-group-specifier :order :most-specific-first)
339            (getf method-group-specifier :required nil))))
340
341(defun parse-qualifier-pattern (name pattern)
342  (cond ((eq pattern '()) `(null .qualifiers.))
343        ((eq pattern '*) t)
344        ((symbolp pattern) `(,pattern .qualifiers.))
345        ((listp pattern) `(qualifier-check-runtime ',pattern .qualifiers.))
346        (t (error "In the method group specifier ~S,~%~
347                   ~S isn't a valid qualifier pattern."
348                  name pattern))))
349
350(defun qualifier-check-runtime (pattern qualifiers)
351  (loop (cond ((and (null pattern) (null qualifiers))
352               (return t))
353              ((eq pattern '*) (return t))
354              ((and pattern qualifiers (eq (car pattern) (car qualifiers)))
355               (pop pattern)
356               (pop qualifiers))
357              (t (return nil)))))
358
359(defun make-default-method-group-description (patterns)
360  (if (cdr patterns)
361      (format nil
362              "methods matching one of the patterns: ~{~S, ~} ~S"
363              (butlast patterns) (car (last patterns)))
364      (format nil
365              "methods matching the pattern: ~S"
366              (car patterns))))
367
368;;; This baby is a complete mess. I can't believe we put it in this
369;;; way. No doubt this is a large part of what drives MLY crazy.
370;;;
371;;; At runtime (when the effective-method is run), we bind an intercept
372;;; lambda-list to the arguments to the generic function.
373;;;
374;;; At compute-effective-method time, the symbols in the :arguments
375;;; option are bound to the symbols in the intercept lambda list.
376;;;
377;;; FIXME: in here we have not one but two mini-copies of a weird
378;;; hybrid of PARSE-LAMBDA-LIST and (obsolete) PARSE-DEFMACRO-LAMBDA-LIST.
379(defun deal-with-args-option (wrapped-body args-lambda-list)
380  (let ((intercept-rebindings
381         (let (rebindings)
382           (dolist (arg args-lambda-list (nreverse rebindings))
383             (unless (member arg lambda-list-keywords :test #'eq)
384               (typecase arg
385                 (symbol (push `(,arg ',arg) rebindings))
386                 (cons
387                  (unless (symbolp (car arg))
388                    (error "invalid lambda-list specifier: ~S." arg))
389                  (push `(,(car arg) ',(car arg)) rebindings))
390                 (t (error "invalid lambda-list-specifier: ~S." arg)))))))
391        (nreq 0)
392        (nopt 0)
393        (whole nil))
394    ;; Count the number of required and optional parameters in
395    ;; ARGS-LAMBDA-LIST into NREQ and NOPT, and set WHOLE to the
396    ;; name of a &WHOLE parameter, if any.
397    (when (member '&whole (rest args-lambda-list))
398      (error 'simple-program-error
399             :format-control "~@<The value of the :ARGUMENTS option of ~
400                DEFINE-METHOD-COMBINATION is~2I~_~S,~I~_but &WHOLE may ~
401                only appear first in the lambda list.~:>"
402             :format-arguments (list args-lambda-list)))
403    (loop with state = 'required
404          for arg in args-lambda-list do
405            (if (memq arg lambda-list-keywords)
406                (setq state arg)
407                (case state
408                  (required (incf nreq))
409                  (&optional (incf nopt))
410                  (&whole (setq whole arg state 'required)))))
411    ;; This assumes that the head of WRAPPED-BODY is a let, and it
412    ;; injects let-bindings of the form (ARG 'SYM) for all variables
413    ;; of the argument-lambda-list; SYM is a gensym.
414    (aver (memq (first wrapped-body) '(let let*)))
415    (setf (second wrapped-body)
416          (append intercept-rebindings (second wrapped-body)))
417    ;; Be sure to fill out the args lambda list so that it can be too
418    ;; short if it wants to.
419    (unless (or (memq '&rest args-lambda-list)
420                (memq '&allow-other-keys args-lambda-list))
421      (let ((aux (memq '&aux args-lambda-list)))
422        (setq args-lambda-list
423              (append (ldiff args-lambda-list aux)
424                      (if (memq '&key args-lambda-list)
425                          '(&allow-other-keys)
426                          '(&rest .ignore.))
427                      aux))))
428    ;; .GENERIC-FUNCTION. is bound to the generic function in the
429    ;; method combination function, and .GF-ARGS* is bound to the
430    ;; generic function arguments in effective method functions
431    ;; created for generic functions having a method combination that
432    ;; uses :ARGUMENTS.
433    ;;
434    ;; The DESTRUCTURING-BIND binds the parameters of the
435    ;; ARGS-LAMBDA-LIST to actual generic function arguments.  Because
436    ;; ARGS-LAMBDA-LIST may be shorter or longer than the generic
437    ;; function's lambda list, which is only known at run time, this
438    ;; destructuring has to be done on a slighly modified list of
439    ;; actual arguments, from which values might be stripped or added.
440    ;;
441    ;; Using one of the variable names in the body inserts a symbol
442    ;; into the effective method, and running the effective method
443    ;; produces the value of actual argument that is bound to the
444    ;; symbol.
445    `(let ((inner-result. ,wrapped-body)
446           (gf-lambda-list (generic-function-lambda-list .generic-function.)))
447       `(destructuring-bind ,',args-lambda-list
448            (frob-combined-method-args
449             .gf-args. ',gf-lambda-list
450             ,',nreq ,',nopt)
451          ,,(when (memq '.ignore. args-lambda-list)
452              ''(declare (ignore .ignore.)))
453          ;; If there is a &WHOLE in the args-lambda-list, let
454          ;; it result in the actual arguments of the generic-function
455          ;; not the frobbed list.
456          ,,(when whole
457              ``(setq ,',whole .gf-args.))
458          ,inner-result.))))
459
460;;; Partition VALUES into three sections: required, optional, and the
461;;; rest, according to required, optional, and other parameters in
462;;; LAMBDA-LIST.  Make the required and optional sections NREQ and
463;;; NOPT elements long by discarding values or adding NILs.  Value is
464;;; the concatenated list of required and optional sections, and what
465;;; is left as rest from VALUES.
466(defun frob-combined-method-args (values lambda-list nreq nopt)
467  (loop with section = 'required
468        for arg in lambda-list
469        if (memq arg lambda-list-keywords) do
470          (setq section arg)
471          (unless (eq section '&optional)
472            (loop-finish))
473        else if (eq section 'required)
474          count t into nr
475          and collect (pop values) into required
476        else if (eq section '&optional)
477          count t into no
478          and collect (pop values) into optional
479        finally
480          (flet ((frob (list n m)
481                   (cond ((> n m) (butlast list (- n m)))
482                         ((< n m) (nconc list (make-list (- m n))))
483                         (t list))))
484            (return (nconc (frob required nr nreq)
485                           (frob optional no nopt)
486                           values)))))
487