1 ;;; cl-generic.el --- CLOS-style generic functions for Elisp -*- lexical-binding: t; -*-
3 ;; Copyright (C) 2015 Free Software Foundation, Inc.
5 ;; Author: Stefan Monnier <monnier@iro.umontreal.ca>
7 ;; This file is part of GNU Emacs.
9 ;; GNU Emacs is free software: you can redistribute it and/or modify
10 ;; it under the terms of the GNU General Public License as published by
11 ;; the Free Software Foundation, either version 3 of the License, or
12 ;; (at your option) any later version.
14 ;; GNU Emacs is distributed in the hope that it will be useful,
15 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
16 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 ;; GNU General Public License for more details.
19 ;; You should have received a copy of the GNU General Public License
20 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
24 ;; This implements the most of CLOS's multiple-dispatch generic functions.
25 ;; To use it you need either (require 'cl-generic) or (require 'cl-lib).
26 ;; The main entry points are: `cl-defgeneric' and `cl-defmethod'.
29 ;; - We don't support make-method, call-method, define-method-combination.
30 ;; CLOS's define-method-combination is IMO overly complicated, and it suffers
31 ;; from a significant problem: the method-combination code returns a sexp
32 ;; that needs to be `eval'uated or compiled. IOW it requires run-time
33 ;; code generation. Given how rarely method-combinations are used,
34 ;; I just provided a cl-generic-method-combination-function, which
35 ;; people can use if they are really desperate for such functionality.
36 ;; - In defgeneric we don't support the options:
37 ;; declare, :method-combination, :generic-function-class, :method-class,
40 ;; - We support aliases to generic functions.
41 ;; - The kind of thing on which to dispatch can be extended.
42 ;; There is support in this file for dispatch on:
45 ;; - type of CL structs
46 ;; eieio-core adds dispatch on:
47 ;; - class of eieio objects
48 ;; - actual class argument, using the syntax (subclass <class>).
49 ;; - cl-generic-method-combination-function (i.s.o define-method-combination).
50 ;; - cl-generic-call-method (which replaces make-method and call-method).
52 ;; Efficiency considerations: overall, I've made an effort to make this fairly
53 ;; efficient for the expected case (e.g. no constant redefinition of methods).
54 ;; - Generic functions which do not dispatch on any argument are implemented
55 ;; optimally (just as efficient as plain old functions).
56 ;; - Generic functions which only dispatch on one argument are fairly efficient
57 ;; (not a lot of room for improvement, I think).
58 ;; - Multiple dispatch is implemented rather naively. There's an extra `apply'
59 ;; function call for every dispatch; we don't optimize each dispatch
60 ;; based on the set of candidate methods remaining; we don't optimize the
61 ;; order in which we performs the dispatches either; If/when this
62 ;; becomes a problem, we can try and optimize it.
63 ;; - call-next-method could be made more efficient, but isn't too terrible.
67 ;; Note: For generic functions that dispatch on several arguments (i.e. those
68 ;; which use the multiple-dispatch feature), we always use the same "tagcodes"
69 ;; and the same set of arguments on which to dispatch. This works, but is
70 ;; often suboptimal since after one dispatch, the remaining dispatches can
71 ;; usually be simplified, or even completely skipped.
74 ;; - WIBNI we could use something like
75 ;; (add-function :before (cl-method-function (cl-find-method ...)) ...)
77 (eval-when-compile (require 'cl-lib))
78 (eval-when-compile (require 'pcase))
80 (defvar cl-generic-tagcode-function
82 (if (eq type t) '(0 . 'cl--generic-type)
83 (error "Unknown specializer %S" type)))
84 "Function to get the Elisp code to extract the tag on which we dispatch.
85 Takes a \"parameter-specializer-name\" and a variable name, and returns
86 a pair (PRIORITY . CODE) where CODE is an Elisp expression that should be
87 used to extract the \"tag\" (from the object held in the named variable)
88 that should uniquely determine if we have a match
89 \(i.e. the \"tag\" is the value that will be used to dispatch to the proper
91 Such \"tagcodes\" will be or'd together.
92 PRIORITY is an integer from 0 to 100 which is used to sort the tagcodes
93 in the `or'. The higher the priority, the more specific the tag should be.
94 More specifically, if PRIORITY is N and we have two objects X and Y
95 whose tag (according to TAGCODE) is `eql', then it should be the case
96 that for all other (PRIORITY . TAGCODE) where PRIORITY ≤ N, then
97 \(eval TAGCODE) for X is `eql' to (eval TAGCODE) for Y.")
99 (defvar cl-generic-tag-types-function
100 (lambda (tag) (if (eq tag 'cl--generic-type) '(t)))
101 "Function to get the list of types that a given \"tag\" matches.
102 They should be sorted from most specific to least specific.")
104 (cl-defstruct (cl--generic-method
106 (:constructor cl--generic-method-make
107 (specializers qualifiers uses-cnm function))
109 (specializers nil :read-only t :type list)
110 (qualifiers nil :read-only t :type (list-of atom))
111 ;; USES-CNM is a boolean indicating if FUNCTION expects an extra argument
112 ;; holding the next-method.
113 (uses-cnm nil :read-only t :type boolean)
114 (function nil :read-only t :type function))
116 (cl-defstruct (cl--generic
118 (:constructor cl--generic-make
119 (name &optional dispatches method-table))
121 (name nil :type symbol :read-only t) ;Pointer back to the symbol.
122 ;; `dispatches' holds a list of (ARGNUM . TAGCODES) where ARGNUM is the index
123 ;; of the corresponding argument and TAGCODES is a list of (PRIORITY . EXP)
124 ;; where the EXPs are expressions (to be `or'd together) to compute the tag
125 ;; on which to dispatch and PRIORITY is the priority of each expression to
126 ;; decide in which order to sort them.
127 ;; The most important dispatch is last in the list (and the least is first).
128 (dispatches nil :type (list-of (cons natnum (list-of tagcode))))
129 (method-table nil :type (list-of cl--generic-method)))
131 (defmacro cl--generic (name)
132 `(get ,name 'cl--generic))
134 (defun cl-generic-ensure-function (name)
137 (while (and (null (setq generic (cl--generic name)))
139 (symbolp (symbol-function name)))
140 (setq name (symbol-function name)))
141 (unless (or (not (fboundp name))
142 (autoloadp (symbol-function name))
143 (and (functionp name) generic))
144 (error "%s is already defined as something else than a generic function"
147 (cl-assert (eq name (cl--generic-name generic)))
148 (setf (cl--generic name) (setq generic (cl--generic-make name)))
149 (defalias name (cl--generic-make-function generic)))
152 (defun cl--generic-setf-rewrite (name)
153 (let* ((setter (intern (format "cl-generic-setter--%s" name)))
154 (exp `(unless (eq ',setter (get ',name 'cl-generic-setter))
155 ;; (when (get ',name 'gv-expander)
156 ;; (error "gv-expander conflicts with (setf %S)" ',name))
157 (setf (get ',name 'cl-generic-setter) ',setter)
158 (gv-define-setter ,name (val &rest args)
159 (cons ',setter (cons val args))))))
160 ;; Make sure `setf' can be used right away, e.g. in the body of the method.
165 (defmacro cl-defgeneric (name args &rest options-and-methods)
166 "Create a generic function NAME.
167 DOC-STRING is the base documentation for this class. A generic
168 function has no body, as its purpose is to decide which method body
169 is appropriate to use. Specific methods are defined with `cl-defmethod'.
170 With this implementation the ARGS are currently ignored.
171 OPTIONS-AND-METHODS currently understands:
172 - (:documentation DOCSTRING)
173 - (declare DECLARATIONS)"
174 (declare (indent 2) (doc-string 3))
175 (let* ((docprop (assq :documentation options-and-methods))
176 (doc (cond ((stringp (car-safe options-and-methods))
177 (pop options-and-methods))
181 (setq options-and-methods
182 (delq docprop options-and-methods))))))
183 (declarations (assq 'declare options-and-methods)))
185 (setq options-and-methods
186 (delq declarations options-and-methods)))
188 ,(when (eq 'setf (car-safe name))
189 (pcase-let ((`(,setter . ,code) (cl--generic-setf-rewrite
193 ,@(mapcar (lambda (declaration)
194 (let ((f (cdr (assq (car declaration)
195 defun-declarations-alist))))
197 (f (apply (car f) name args (cdr declaration)))
198 (t (message "Warning: Unknown defun property `%S' in %S"
199 (car declaration) name)
203 (cl-generic-define ',name ',args ',options-and-methods)
204 ,(help-add-fundoc-usage doc args)))))
206 (defun cl--generic-mandatory-args (args)
208 (while (not (memq (car args) '(nil &rest &optional &key)))
209 (push (pop args) res))
213 (defun cl-generic-define (name args options-and-methods)
214 (let ((generic (cl-generic-ensure-function name))
215 (mandatory (cl--generic-mandatory-args args))
216 (apo (assq :argument-precedence-order options-and-methods)))
217 (setf (cl--generic-dispatches generic) nil)
219 (dolist (arg (cdr apo))
220 (let ((pos (memq arg mandatory)))
221 (unless pos (error "%S is not a mandatory argument" arg))
222 (push (list (- (length mandatory) (length pos)))
223 (cl--generic-dispatches generic)))))
224 (setf (cl--generic-method-table generic) nil)
225 (cl--generic-make-function generic)))
227 (defmacro cl-generic-current-method-specializers ()
228 "List of (VAR . TYPE) where TYPE is var's specializer.
229 This macro can only be used within the lexical scope of a cl-generic method."
230 (error "cl-generic-current-method-specializers used outside of a method"))
232 (eval-and-compile ;Needed while compiling the cl-defmethod calls below!
233 (defun cl--generic-fgrep (vars sexp) ;Copied from pcase.el.
234 "Check which of the symbols VARS appear in SEXP."
237 (dolist (var (cl--generic-fgrep vars (pop sexp)))
238 (unless (memq var res) (push var res))))
239 (and (memq sexp vars) (not (memq sexp res)) (push sexp res))
242 (defun cl--generic-lambda (args body)
243 "Make the lambda expression for a method with ARGS and BODY."
244 (let ((plain-args ())
249 ((or '&optional '&rest '&key) (setq mandatory nil) arg)
250 ((and `(,name . ,type) (guard mandatory))
251 (push (cons name (car type)) specializers)
255 (setq plain-args (nreverse plain-args))
256 (let ((fun `(cl-function (lambda ,plain-args ,@body)))
257 (macroenv (cons `(cl-generic-current-method-specializers
258 . ,(lambda () specializers))
259 macroexpand-all-environment)))
260 (require 'cl-lib) ;Needed to expand `cl-flet' and `cl-function'.
261 ;; First macroexpand away the cl-function stuff (e.g. &key and
262 ;; destructuring args, `declare' and whatnot).
263 (pcase (macroexpand fun macroenv)
264 (`#'(lambda ,args . ,body)
265 (let* ((parsed-body (macroexp-parse-body body))
266 (cnm (make-symbol "cl--cnm"))
267 (nmp (make-symbol "cl--nmp"))
268 (nbody (macroexpand-all
269 `(cl-flet ((cl-call-next-method ,cnm)
270 (cl-next-method-p ,nmp))
273 ;; FIXME: Rather than `grep' after the fact, the
274 ;; macroexpansion should directly set some flag when cnm
276 ;; FIXME: Also, optimize the case where call-next-method is
277 ;; only called with explicit arguments.
278 (uses-cnm (cl--generic-fgrep (list cnm nmp) nbody)))
279 (cons (not (not uses-cnm))
280 `#'(lambda (,@(if uses-cnm (list cnm)) ,@args)
282 ,(if (not (memq nmp uses-cnm))
284 `(let ((,nmp (lambda ()
285 (cl--generic-isnot-nnm-p ,cnm))))
287 (f (error "Unexpected macroexpansion result: %S" f)))))))
291 (defmacro cl-defmethod (name args &rest body)
292 "Define a new method for generic function NAME.
293 I.e. it defines the implementation of NAME to use for invocations where the
294 value of the dispatch argument matches the specified TYPE.
295 The dispatch argument has to be one of the mandatory arguments, and
296 all methods of NAME have to use the same argument for dispatch.
297 The dispatch argument and TYPE are specified in ARGS where the corresponding
298 formal argument appears as (VAR TYPE) rather than just VAR.
300 The optional second argument QUALIFIER is a specifier that
301 modifies how the method is combined with other methods, including:
302 :before - Method will be called before the primary
303 :after - Method will be called after the primary
304 :around - Method will be called around everything else
305 The absence of QUALIFIER means this is a \"primary\" method.
307 Other than a type, TYPE can also be of the form `(eql VAL)' in
308 which case this method will be invoked when the argument is `eql' to VAL.
310 \(fn NAME [QUALIFIER] ARGS &rest [DOCSTRING] BODY)"
311 (declare (doc-string 3) (indent 2)
313 (&define ; this means we are defining something
314 [&or name ("setf" :name setf name)]
315 ;; ^^ This is the methods symbol
316 [ &optional keywordp ] ; this is key :before etc
318 [ &optional stringp ] ; documentation string
319 def-body))) ; part to be debugged
320 (let ((qualifiers nil)
321 (setfizer (if (eq 'setf (car-safe name))
322 ;; Call it before we call cl--generic-lambda.
323 (cl--generic-setf-rewrite (cadr name)))))
324 (while (not (listp args))
325 (push args qualifiers)
326 (setq args (pop body)))
327 (pcase-let* ((`(,uses-cnm . ,fun) (cl--generic-lambda args body)))
330 (setq name (car setfizer))
332 ,(and (get name 'byte-obsolete-info)
333 (or (not (fboundp 'byte-compile-warning-enabled-p))
334 (byte-compile-warning-enabled-p 'obsolete))
335 (let* ((obsolete (get name 'byte-obsolete-info)))
336 (macroexp--warn-and-return
337 (macroexp--obsolete-warning name obsolete "generic function")
339 ;; You could argue that `defmethod' modifies rather than defines the
340 ;; function, so warnings like "not known to be defined" are fair game.
341 ;; But in practice, it's common to use `cl-defmethod'
342 ;; without a previous `cl-defgeneric'.
343 (declare-function ,name "")
344 (cl-generic-define-method ',name ',qualifiers ',args
347 (defun cl--generic-member-method (specializers qualifiers methods)
350 (let ((m (car methods)))
351 (not (and (equal (cl--generic-method-specializers m) specializers)
352 (equal (cl--generic-method-qualifiers m) qualifiers)))))
353 (setq methods (cdr methods)))
357 (defun cl-generic-define-method (name qualifiers args uses-cnm function)
358 (let* ((generic (cl-generic-ensure-function name))
359 (mandatory (cl--generic-mandatory-args args))
361 (mapcar (lambda (arg) (if (consp arg) (cadr arg) t)) mandatory))
362 (method (cl--generic-method-make
363 specializers qualifiers uses-cnm function))
364 (mt (cl--generic-method-table generic))
365 (me (cl--generic-member-method specializers qualifiers mt))
366 (dispatches (cl--generic-dispatches generic))
368 (dolist (specializer specializers)
369 (let* ((tagcode (funcall cl-generic-tagcode-function specializer 'arg))
370 (x (assq i dispatches)))
372 (setq x (list i (funcall cl-generic-tagcode-function t 'arg)))
373 (setf (cl--generic-dispatches generic)
374 (setq dispatches (cons x dispatches))))
375 (unless (member tagcode (cdr x))
377 (nreverse (sort (cons tagcode (cdr x))
378 #'car-less-than-car))))
380 (if me (setcar me method)
381 (setf (cl--generic-method-table generic) (cons method mt)))
382 (cl-pushnew `(cl-defmethod . (,(cl--generic-name generic) . ,specializers))
383 current-load-list :test #'equal)
384 (let ((gfun (cl--generic-make-function generic))
385 ;; Prevent `defalias' from recording this as the definition site of
386 ;; the generic function.
388 ;; For aliases, cl--generic-name gives us the actual name.
389 (defalias (cl--generic-name generic) gfun))))
391 (defmacro cl--generic-with-memoization (place &rest code)
392 (declare (indent 1) (debug t))
393 (gv-letplace (getter setter) place
395 ,(macroexp-let2 nil val (macroexp-progn code)
397 ,(funcall setter val)
400 (defvar cl--generic-dispatchers (make-hash-table :test #'equal))
402 (defun cl--generic-get-dispatcher (tagcodes dispatch-arg)
403 (cl--generic-with-memoization
404 (gethash (cons dispatch-arg tagcodes) cl--generic-dispatchers)
405 (let ((lexical-binding t)
406 (tag-exp `(or ,@(mapcar #'cdr
407 ;; Minor optimization: since this tag-exp is
408 ;; only used to lookup the method-cache, it
409 ;; doesn't matter if the default value is some
411 (if (macroexp-const-p (car (last tagcodes)))
415 (dotimes (_ dispatch-arg)
416 (push (make-symbol "arg") extraargs))
418 `(lambda (generic dispatches-left)
419 (let ((method-cache (make-hash-table :test #'eql)))
420 (lambda (,@extraargs arg &rest args)
421 (apply (cl--generic-with-memoization
422 (gethash ,tag-exp method-cache)
423 (cl--generic-cache-miss
424 generic ',dispatch-arg dispatches-left
425 (list ,@(mapcar #'cdr tagcodes))))
426 ,@extraargs arg args))))))))
428 (defun cl--generic-make-function (generic)
429 (let* ((dispatches (cl--generic-dispatches generic))
432 (while (and dispatches
433 (member (cdar dispatches)
434 '(nil ((0 . 'cl--generic-type)))))
435 (setq dispatches (cdr dispatches)))
438 (cl--generic-build-combined-method
439 (cl--generic-name generic)
440 (cl--generic-method-table generic))
441 (let ((dispatcher (cl--generic-get-dispatcher
442 (cdr dispatch) (car dispatch))))
443 (funcall dispatcher generic dispatches)))))
445 (defvar cl-generic-method-combination-function
446 #'cl--generic-standard-method-combination
447 "Function to build the effective method.
448 Called with 2 arguments: NAME and METHOD-ALIST.
449 It should return an effective method, i.e. a function that expects the same
450 arguments as the methods, and calls those methods in some appropriate order.
451 NAME is the name (a symbol) of the corresponding generic function.
452 METHOD-ALIST is a list of elements (QUALIFIERS . METHODS) where
453 QUALIFIERS is a list of qualifiers, and METHODS is a list of the selected
454 methods for that qualifier list.
455 The METHODS lists are sorted from most generic first to most specific last.
456 The function can use `cl-generic-call-method' to create functions that call those
459 (defvar cl--generic-combined-method-memoization
460 (make-hash-table :test #'equal :weakness 'value)
461 "Table storing previously built combined-methods.
462 This is particularly useful when many different tags select the same set
463 of methods, since this table then allows us to share a single combined-method
464 for all those different tags in the method-cache.")
466 (defun cl--generic-build-combined-method (generic-name methods)
467 (cl--generic-with-memoization
468 (gethash (cons generic-name methods)
469 cl--generic-combined-method-memoization)
470 (let ((mets-by-qual ()))
471 (dolist (method methods)
472 (let* ((qualifiers (cl--generic-method-qualifiers method))
473 (x (assoc qualifiers mets-by-qual)))
474 ;; FIXME: sadly, alist-get only uses `assq' and we need `assoc'.
475 ;;(push (cdr qm) (alist-get qualifiers mets-by-qual)))
477 (push method (cdr x))
478 (push (list qualifiers method) mets-by-qual))))
479 (funcall cl-generic-method-combination-function
480 generic-name mets-by-qual))))
482 (defun cl--generic-no-next-method-function (generic method)
484 (apply #'cl-no-next-method generic method args)))
486 (defun cl-generic-call-method (generic-name method &optional fun)
487 "Return a function that calls METHOD.
488 FUN is the function that should be called when METHOD calls
490 (if (not (cl--generic-method-uses-cnm method))
491 (cl--generic-method-function method)
492 (let ((met-fun (cl--generic-method-function method))
493 (next (or fun (cl--generic-no-next-method-function
494 generic-name method))))
497 ;; FIXME: This sucks: passing just `next' would
498 ;; be a lot more efficient than the lambda+apply
499 ;; quasi-η, but we need this to implement the
500 ;; "if call-next-method is called with no
501 ;; arguments, then use the previous arguments".
502 (lambda (&rest cnm-args)
503 (apply next (or cnm-args args)))
506 (defun cl--generic-standard-method-combination (generic-name mets-by-qual)
507 (dolist (x mets-by-qual)
508 (unless (member (car x) '(() (:after) (:before) (:around)))
509 (error "Unsupported qualifiers in function %S: %S" generic-name (car x))))
513 (apply #'cl-no-applicable-method generic-name args)))
514 ((null (alist-get nil mets-by-qual))
516 (apply #'cl-no-primary-method generic-name args)))
519 (ab-call (lambda (m) (cl-generic-call-method generic-name m)))
521 (mapcar ab-call (reverse (cdr (assoc '(:before) mets-by-qual)))))
522 (after (mapcar ab-call (cdr (assoc '(:after) mets-by-qual)))))
523 (dolist (method (cdr (assoc nil mets-by-qual)))
524 (setq fun (cl-generic-call-method generic-name method fun)))
525 (when (or after before)
527 (setq fun (lambda (&rest args)
533 (apply af args)))))))
534 (dolist (method (cdr (assoc '(:around) mets-by-qual)))
535 (setq fun (cl-generic-call-method generic-name method fun)))
538 (defconst cl--generic-nnm-sample (cl--generic-no-next-method-function t t))
539 (defconst cl--generic-cnm-sample
540 (funcall (cl--generic-build-combined-method
541 nil (list (cl--generic-method-make () () t #'identity)))))
543 (defun cl--generic-isnot-nnm-p (cnm)
544 "Return non-nil if CNM is the function that calls `cl-no-next-method'."
545 ;; ¡Big Gross Ugly Hack!
546 ;; `next-method-p' just sucks, we should let it die. But EIEIO did support
547 ;; it, and some packages use it, so we need to support it.
549 (cl-assert (function-equal cnm cl--generic-cnm-sample))
550 (if (byte-code-function-p cnm)
551 (let ((cnm-constants (aref cnm 2))
552 (sample-constants (aref cl--generic-cnm-sample 2)))
553 (dotimes (i (length sample-constants))
554 (when (function-equal (aref sample-constants i)
555 cl--generic-nnm-sample)
557 (not (function-equal (aref cnm-constants i)
558 cl--generic-nnm-sample))))))
559 (cl-assert (eq 'closure (car-safe cl--generic-cnm-sample)))
560 (let ((cnm-env (cadr cnm)))
561 (dolist (vb (cadr cl--generic-cnm-sample))
562 (when (function-equal (cdr vb) cl--generic-nnm-sample)
564 (not (function-equal (cdar cnm-env)
565 cl--generic-nnm-sample))))
566 (setq cnm-env (cdr cnm-env)))))
567 (error "Haven't found no-next-method-sample in cnm-sample")))
569 (defun cl--generic-cache-miss (generic dispatch-arg dispatches-left tags)
570 (let ((types (apply #'append (mapcar cl-generic-tag-types-function tags)))
572 (dolist (method (cl--generic-method-table generic))
573 (let* ((specializer (or (nth dispatch-arg
574 (cl--generic-method-specializers method))
576 (m (member specializer types)))
578 (push (cons (length m) method) methods))))
579 ;; Sort the methods, most specific first.
580 ;; It would be tempting to sort them once and for all in the method-table
581 ;; rather than here, but the order might depend on the actual argument
582 ;; (e.g. for multiple inheritance with defclass).
583 (setq methods (nreverse (mapcar #'cdr (sort methods #'car-less-than-car))))
584 (cl--generic-make-function (cl--generic-make (cl--generic-name generic)
585 dispatches-left methods))))
587 ;;; Define some pre-defined generic functions, used internally.
589 (define-error 'cl-no-method "No method for %S")
590 (define-error 'cl-no-next-method "No next method for %S" 'cl-no-method)
591 (define-error 'cl-no-primary-method "No primary method for %S" 'cl-no-method)
592 (define-error 'cl-no-applicable-method "No applicable method for %S"
595 (cl-defgeneric cl-no-next-method (generic method &rest args)
596 "Function called when `cl-call-next-method' finds no next method.")
597 (cl-defmethod cl-no-next-method (generic method &rest args)
598 (signal 'cl-no-next-method `(,generic ,method ,@args)))
600 (cl-defgeneric cl-no-applicable-method (generic &rest args)
601 "Function called when a method call finds no applicable method.")
602 (cl-defmethod cl-no-applicable-method (generic &rest args)
603 (signal 'cl-no-applicable-method `(,generic ,@args)))
605 (cl-defgeneric cl-no-primary-method (generic &rest args)
606 "Function called when a method call finds no primary method.")
607 (cl-defmethod cl-no-primary-method (generic &rest args)
608 (signal 'cl-no-primary-method `(,generic ,@args)))
610 (defun cl-call-next-method (&rest _args)
611 "Function to call the next applicable method.
612 Can only be used from within the lexical body of a primary or around method."
613 (error "cl-call-next-method only allowed inside primary and around methods"))
615 (defun cl-next-method-p ()
616 "Return non-nil if there is a next method.
617 Can only be used from within the lexical body of a primary or around method."
618 (declare (obsolete "make sure there's always a next method, or catch `cl-no-next-method' instead" "25.1"))
619 (error "cl-next-method-p only allowed inside primary and around methods"))
622 (defun cl-find-method (generic qualifiers specializers)
623 (car (cl--generic-member-method
624 specializers qualifiers
625 (cl--generic-method-table (cl--generic generic)))))
627 (defalias 'cl-method-qualifiers 'cl--generic-method-qualifiers)
629 ;;; Add support for describe-function
631 (defun cl--generic-search-method (met-name)
632 (let ((base-re (concat "(\\(?:cl-\\)?defmethod[ \t]+"
633 (regexp-quote (format "%s" (car met-name)))
637 (concat base-re "[^&\"\n]*"
638 (mapconcat (lambda (specializer)
640 (format "%S" (if (consp specializer)
641 (nth 1 specializer) specializer))))
642 (remq t (cdr met-name))
643 "[ \t\n]*)[^&\"\n]*"))
645 (re-search-forward base-re nil t))))
648 (with-eval-after-load 'find-func
649 (defvar find-function-regexp-alist)
650 (add-to-list 'find-function-regexp-alist
651 `(cl-defmethod . ,#'cl--generic-search-method)))
653 (defun cl--generic-method-info (method)
654 (let* ((specializers (cl--generic-method-specializers method))
655 (qualifiers (cl--generic-method-qualifiers method))
656 (uses-cnm (cl--generic-method-uses-cnm method))
657 (function (cl--generic-method-function method))
658 (args (help-function-arglist function 'names))
659 (docstring (documentation function))
661 (if (null qualifiers) ""
662 (cl-assert (consp qualifiers))
663 (let ((s (prin1-to-string qualifiers)))
664 (concat (substring s 1 -1) " "))))
665 (doconly (if docstring
666 (let ((split (help-split-fundoc docstring nil)))
667 (if split (cdr split) docstring))))
669 (if uses-cnm (setq args (cdr args)))
670 (dolist (specializer specializers)
671 (let ((arg (if (eq '&rest (car args))
672 (intern (format "arg%d" (length combined-args)))
674 (push (if (eq specializer t) arg (list arg specializer))
676 (setq combined-args (append (nreverse combined-args) args))
677 (list qual-string combined-args doconly)))
679 (add-hook 'help-fns-describe-function-functions #'cl--generic-describe)
680 (defun cl--generic-describe (function)
681 (let ((generic (if (symbolp function) (cl--generic function))))
683 (require 'help-mode) ;Needed for `help-function-def' button!
685 (insert "\n\nThis is a generic function.\n\n")
686 (insert (propertize "Implementations:\n\n" 'face 'bold))
687 ;; Loop over fanciful generics
688 (dolist (method (cl--generic-method-table generic))
689 (let* ((info (cl--generic-method-info method)))
690 ;; FIXME: Add hyperlinks for the types as well.
691 (insert (format "%s%S" (nth 0 info) (nth 1 info)))
692 (let* ((met-name (cons function
693 (cl--generic-method-specializers method)))
694 (file (find-lisp-object-file-name met-name 'cl-defmethod)))
697 (help-insert-xref-button (help-fns-short-filename file)
698 'help-function-def met-name file
701 (insert "\n" (or (nth 2 info) "Undocumented") "\n\n")))))))
703 ;;; Support for (eql <val>) specializers.
705 (defvar cl--generic-eql-used (make-hash-table :test #'eql))
707 (add-function :before-until cl-generic-tagcode-function
708 #'cl--generic-eql-tagcode)
709 (defun cl--generic-eql-tagcode (type name)
710 (when (eq (car-safe type) 'eql)
711 (puthash (cadr type) type cl--generic-eql-used)
712 `(100 . (gethash ,name cl--generic-eql-used))))
714 (add-function :before-until cl-generic-tag-types-function
715 #'cl--generic-eql-tag-types)
716 (defun cl--generic-eql-tag-types (tag)
717 (if (eq (car-safe tag) 'eql) (list tag)))
719 ;;; Support for cl-defstructs specializers.
721 (add-function :before-until cl-generic-tagcode-function
722 #'cl--generic-struct-tagcode)
724 (defun cl--generic-struct-tag (name)
725 `(and (vectorp ,name)
727 (let ((tag (aref ,name 0)))
728 (if (eq (symbol-function tag) :quick-object-witness-check)
731 (defun cl--generic-struct-tagcode (type name)
733 (get type 'cl-struct-type)
734 (or (null (car (get type 'cl-struct-type)))
735 (error "Can't dispatch on cl-struct %S: type is %S"
736 type (car (get type 'cl-struct-type))))
737 (or (equal '(cl-tag-slot) (car (get type 'cl-struct-slots)))
738 (error "Can't dispatch on cl-struct %S: no tag in slot 0"
740 ;; It's tempting to use (and (vectorp ,name) (aref ,name 0))
741 ;; but that would suffer from some problems:
742 ;; - the vector may have size 0.
743 ;; - when called on an actual vector (rather than an object), we'd
744 ;; end up returning an arbitrary value, possibly colliding with
745 ;; other tagcode's values.
746 ;; - it can also result in returning all kinds of irrelevant
747 ;; values which would end up filling up the method-cache with
748 ;; lots of irrelevant/redundant entries.
749 ;; FIXME: We could speed this up by introducing a dedicated
750 ;; vector type at the C level, so we could do something like
751 ;; (and (vector-objectp ,name) (aref ,name 0))
752 `(50 . ,(cl--generic-struct-tag name))))
754 (add-function :before-until cl-generic-tag-types-function
755 #'cl--generic-struct-tag-types)
756 (defun cl--generic-struct-tag-types (tag)
757 ;; FIXME: cl-defstruct doesn't make it easy for us.
759 ;; A method call shouldn't itself mess with the match-data.
760 (string-match-p "\\`cl-struct-\\(.*\\)" (symbol-name tag))
761 (let ((types (list (intern (substring (symbol-name tag) 10)))))
762 (while (get (car types) 'cl-struct-include)
763 (push (get (car types) 'cl-struct-include) types))
764 (push 'cl-structure-object types) ;The "parent type" of all cl-structs.
767 ;;; Dispatch on "system types".
769 (defconst cl--generic-typeof-types
770 ;; Hand made from the source code of `type-of'.
771 '((integer number) (symbol) (string array sequence) (cons list sequence)
772 ;; Markers aren't `numberp', yet they are accepted wherever integers are
773 ;; accepted, pretty much.
774 (marker) (overlay) (float number) (window-configuration)
775 (process) (window) (subr) (compiled-function) (buffer)
776 (char-table array sequence)
777 (bool-vector array sequence)
778 (frame) (hash-table) (font-spec) (font-entity) (font-object)
779 (vector array sequence)
781 (null symbol list sequence)
787 (add-function :before-until cl-generic-tagcode-function
788 #'cl--generic-typeof-tagcode)
789 (defun cl--generic-typeof-tagcode (type name)
790 ;; FIXME: Add support for other types accepted by `cl-typep' such
791 ;; as `character', `atom', `face', `function', ...
792 (and (assq type cl--generic-typeof-types)
794 (if (memq type '(vector array sequence))
795 (message "`%S' also matches CL structs and EIEIO classes" type))
796 ;; FIXME: We could also change `type-of' to return `null' for nil.
797 `(10 . (if ,name (type-of ,name) 'null)))))
799 (add-function :before-until cl-generic-tag-types-function
800 #'cl--generic-typeof-types)
801 (defun cl--generic-typeof-types (tag)
803 (assq tag cl--generic-typeof-types)))
805 ;;; Just for kicks: dispatch on major-mode
807 ;; Here's how you'd use it:
808 ;; (cl-defmethod foo ((x (major-mode text-mode)) y z) ...)
810 ;; (foo 'major-mode toto titi)
812 ;; FIXME: Better would be to do that via dispatch on an "implicit argument".
813 ;; E.g. (cl-defmethod foo (y z &context (major-mode text-mode)) ...)
815 ;; (defvar cl--generic-major-modes (make-hash-table :test #'eq))
817 ;; (add-function :before-until cl-generic-tagcode-function
818 ;; #'cl--generic-major-mode-tagcode)
819 ;; (defun cl--generic-major-mode-tagcode (type name)
820 ;; (if (eq 'major-mode (car-safe type))
821 ;; `(50 . (if (eq ,name 'major-mode)
822 ;; (cl--generic-with-memoization
823 ;; (gethash major-mode cl--generic-major-modes)
824 ;; `(cl--generic-major-mode . ,major-mode))))))
826 ;; (add-function :before-until cl-generic-tag-types-function
827 ;; #'cl--generic-major-mode-types)
828 ;; (defun cl--generic-major-mode-types (tag)
829 ;; (when (eq (car-safe tag) 'cl--generic-major-mode)
830 ;; (if (eq tag 'fundamental-mode) '(fundamental-mode t)
831 ;; (let ((types `((major-mode ,(cdr tag)))))
832 ;; (while (get (car types) 'derived-mode-parent)
833 ;; (push (list 'major-mode (get (car types) 'derived-mode-parent))
835 ;; (unless (eq 'fundamental-mode (car types))
836 ;; (push '(major-mode fundamental-mode) types))
837 ;; (nreverse types)))))
840 ;; generated-autoload-file: "cl-loaddefs.el"
843 (provide 'cl-generic)
844 ;;; cl-generic.el ends here