1 ;;;; bootstrapping the meta-braid
3 ;;;; The code in this file takes the early definitions that have been
4 ;;;; saved up and actually builds those class objects. This work is
5 ;;;; largely driven off of those class definitions, but the fact that
6 ;;;; STANDARD-CLASS is the class of all metaclasses in the braid is
7 ;;;; built into this code pretty deeply.
9 ;;;; This software is part of the SBCL system. See the README file for
10 ;;;; more information.
12 ;;;; This software is derived from software originally released by Xerox
13 ;;;; Corporation. Copyright and release statements follow. Later modifications
14 ;;;; to the software are in the public domain and are provided with
15 ;;;; absolutely no warranty. See the COPYING and CREDITS files for more
18 ;;;; copyright information from original PCL sources:
20 ;;;; Copyright (c) 1985, 1986, 1987, 1988, 1989, 1990 Xerox Corporation.
21 ;;;; All rights reserved.
23 ;;;; Use and copying of this software and preparation of derivative works based
24 ;;;; upon this software are permitted. Any distribution of this software or
25 ;;;; derivative works must comply with all applicable United States export
28 ;;;; This software is made available AS IS, and Xerox Corporation makes no
29 ;;;; warranty about the software, its performance or its conformity to any
34 (defun allocate-standard-instance (wrapper
35 &optional (slots-init nil slots-init-p))
36 (let ((instance (%make-standard-instance nil (get-instance-hash-code)))
37 (no-of-slots (wrapper-no-of-instance-slots wrapper)))
38 (setf (std-instance-wrapper instance) wrapper)
39 (setf (std-instance-slots instance)
41 ;; Inline the slots vector allocation and initialization.
42 (let ((slots (make-array no-of-slots :initial-element 0)))
43 (do ((rem-slots slots-init (rest rem-slots))
45 ((>= i no-of-slots)) ;endp rem-slots))
46 (declare (list rem-slots)
48 (setf (aref slots i) (first rem-slots)))
51 (make-array no-of-slots
52 :initial-element +slot-unbound+))))
55 (defmacro allocate-funcallable-instance-slots (wrapper &optional
56 slots-init-p slots-init)
57 `(let ((no-of-slots (wrapper-no-of-instance-slots ,wrapper)))
60 (make-array no-of-slots :initial-contents ,slots-init)
61 (make-array no-of-slots :initial-element +slot-unbound+))
62 `(make-array no-of-slots :initial-element +slot-unbound+))))
64 (defun allocate-funcallable-instance (wrapper &optional
65 (slots-init nil slots-init-p))
66 (let ((fin (%make-pcl-funcallable-instance nil nil
67 (get-instance-hash-code))))
68 (set-funcallable-instance-function
70 #'(instance-lambda (&rest args)
71 (declare (ignore args))
72 (error "The function of the funcallable-instance ~S has not been set."
74 (setf (fsc-instance-wrapper fin) wrapper
75 (fsc-instance-slots fin) (allocate-funcallable-instance-slots
76 wrapper slots-init-p slots-init))
79 (defun allocate-structure-instance (wrapper &optional
80 (slots-init nil slots-init-p))
81 (let* ((class (wrapper-class wrapper))
82 (constructor (class-defstruct-constructor class)))
84 (let ((instance (funcall constructor))
85 (slots (class-slots class)))
88 (setf (slot-value-using-class class instance slot)
91 (error "can't allocate an instance of class ~S" (class-name class)))))
93 ;;;; BOOTSTRAP-META-BRAID
95 ;;;; This function builds the base metabraid from the early class definitions.
97 (defmacro !initial-classes-and-wrappers (&rest classes)
99 ,@(mapcar (lambda (class)
100 (let ((wr (intern (format nil "~A-WRAPPER" class)
102 `(setf ,wr ,(if (eq class 'standard-generic-function)
105 (early-class-size ',class)
107 ,class (allocate-standard-instance
108 ,(if (eq class 'standard-generic-function)
109 'funcallable-standard-class-wrapper
110 'standard-class-wrapper))
111 (wrapper-class ,wr) ,class
112 (find-class ',class) ,class)))
115 (defun !bootstrap-meta-braid ()
116 (let* ((*create-classes-from-internal-structure-definitions-p* nil)
117 std-class-wrapper std-class
118 standard-class-wrapper standard-class
119 funcallable-standard-class-wrapper funcallable-standard-class
120 slot-class-wrapper slot-class
121 built-in-class-wrapper built-in-class
122 structure-class-wrapper structure-class
123 standard-direct-slot-definition-wrapper
124 standard-direct-slot-definition
125 standard-effective-slot-definition-wrapper
126 standard-effective-slot-definition
127 class-eq-specializer-wrapper class-eq-specializer
128 standard-generic-function-wrapper standard-generic-function)
129 (!initial-classes-and-wrappers
130 standard-class funcallable-standard-class
131 slot-class built-in-class structure-class std-class
132 standard-direct-slot-definition standard-effective-slot-definition
133 class-eq-specializer standard-generic-function)
134 ;; First, make a class metaobject for each of the early classes. For
135 ;; each metaobject we also set its wrapper. Except for the class T,
136 ;; the wrapper is always that of STANDARD-CLASS.
137 (dolist (definition *early-class-definitions*)
138 (let* ((name (ecd-class-name definition))
139 (meta (ecd-metaclass definition))
141 (slot-class slot-class-wrapper)
142 (std-class std-class-wrapper)
143 (standard-class standard-class-wrapper)
144 (funcallable-standard-class
145 funcallable-standard-class-wrapper)
146 (built-in-class built-in-class-wrapper)
147 (structure-class structure-class-wrapper)))
148 (class (or (find-class name nil)
149 (allocate-standard-instance wrapper))))
150 (setf (find-class name) class)))
151 (dolist (definition *early-class-definitions*)
152 (let ((name (ecd-class-name definition))
153 (meta (ecd-metaclass definition))
154 (source (ecd-source definition))
155 (direct-supers (ecd-superclass-names definition))
156 (direct-slots (ecd-canonical-slots definition))
157 (other-initargs (ecd-other-initargs definition)))
158 (let ((direct-default-initargs
159 (getf other-initargs :direct-default-initargs)))
160 (multiple-value-bind (slots cpl default-initargs direct-subclasses)
161 (early-collect-inheritance name)
162 (let* ((class (find-class name))
163 (wrapper (cond ((eq class slot-class)
165 ((eq class std-class)
167 ((eq class standard-class)
168 standard-class-wrapper)
169 ((eq class funcallable-standard-class)
170 funcallable-standard-class-wrapper)
171 ((eq class standard-direct-slot-definition)
172 standard-direct-slot-definition-wrapper)
174 standard-effective-slot-definition)
175 standard-effective-slot-definition-wrapper)
176 ((eq class built-in-class)
177 built-in-class-wrapper)
178 ((eq class structure-class)
179 structure-class-wrapper)
180 ((eq class class-eq-specializer)
181 class-eq-specializer-wrapper)
182 ((eq class standard-generic-function)
183 standard-generic-function-wrapper)
185 (boot-make-wrapper (length slots) name))))
187 (when (eq name t) (setq *the-wrapper-of-t* wrapper))
188 (set (intern (format nil "*THE-CLASS-~A*" (symbol-name name))
192 (unless (eq (getf slot :allocation :instance) :instance)
193 (error "Slot allocation ~S is not supported in bootstrap.")))
195 (when (typep wrapper 'wrapper)
196 (setf (wrapper-instance-slots-layout wrapper)
197 (mapcar #'canonical-slot-name slots))
198 (setf (wrapper-class-slots wrapper)
201 (setq proto (if (eq meta 'funcallable-standard-class)
202 (allocate-funcallable-instance wrapper)
203 (allocate-standard-instance wrapper)))
206 (!bootstrap-make-slot-definitions
207 name class direct-slots
208 standard-direct-slot-definition-wrapper nil))
210 (!bootstrap-make-slot-definitions
212 standard-effective-slot-definition-wrapper t))
215 ((std-class standard-class funcallable-standard-class)
216 (!bootstrap-initialize-class
218 class name class-eq-specializer-wrapper source
219 direct-supers direct-subclasses cpl wrapper proto
220 direct-slots slots direct-default-initargs default-initargs))
221 (built-in-class ; *the-class-t*
222 (!bootstrap-initialize-class
224 class name class-eq-specializer-wrapper source
225 direct-supers direct-subclasses cpl wrapper proto))
226 (slot-class ; *the-class-slot-object*
227 (!bootstrap-initialize-class
229 class name class-eq-specializer-wrapper source
230 direct-supers direct-subclasses cpl wrapper proto))
231 (structure-class ; *the-class-structure-object*
232 (!bootstrap-initialize-class
234 class name class-eq-specializer-wrapper source
235 direct-supers direct-subclasses cpl wrapper))))))))
237 (let* ((smc-class (find-class 'standard-method-combination))
238 (smc-wrapper (!bootstrap-get-slot 'standard-class
241 (smc (allocate-standard-instance smc-wrapper)))
242 (flet ((set-slot (name value)
243 (!bootstrap-set-slot 'standard-method-combination
247 (set-slot 'source *load-pathname*)
248 (set-slot 'type 'standard)
249 (set-slot 'documentation "The standard method combination.")
250 (set-slot 'options ()))
251 (setq *standard-method-combination* smc))))
253 ;;; Initialize a class metaobject.
254 (defun !bootstrap-initialize-class
255 (metaclass-name class name
256 class-eq-wrapper source direct-supers direct-subclasses cpl wrapper
259 direct-slots slots direct-default-initargs default-initargs)
260 (flet ((classes (names) (mapcar #'find-class names))
261 (set-slot (slot-name value)
262 (!bootstrap-set-slot metaclass-name class slot-name value)))
263 (set-slot 'name name)
264 (set-slot 'finalized-p t)
265 (set-slot 'source source)
266 (set-slot 'type (if (eq class (find-class t))
268 ;; FIXME: Could this just be CLASS instead
269 ;; of `(CLASS ,CLASS)? If not, why not?
270 ;; (See also similar expression in
271 ;; SHARED-INITIALIZE :BEFORE (CLASS).)
273 (set-slot 'class-eq-specializer
274 (let ((spec (allocate-standard-instance class-eq-wrapper)))
275 (!bootstrap-set-slot 'class-eq-specializer spec 'type
277 (!bootstrap-set-slot 'class-eq-specializer spec 'object
280 (set-slot 'class-precedence-list (classes cpl))
281 (set-slot 'can-precede-list (classes (cdr cpl)))
282 (set-slot 'incompatible-superclass-list nil)
283 (set-slot 'direct-superclasses (classes direct-supers))
284 (set-slot 'direct-subclasses (classes direct-subclasses))
285 (set-slot 'direct-methods (cons nil nil))
286 (set-slot 'wrapper wrapper)
287 (set-slot 'predicate-name (or (cadr (assoc name *early-class-predicates*))
288 (make-class-predicate-name name)))
290 `(,@(and direct-default-initargs
291 `(direct-default-initargs ,direct-default-initargs))
292 ,@(and default-initargs
293 `(default-initargs ,default-initargs))))
294 (when (memq metaclass-name '(standard-class funcallable-standard-class
295 structure-class slot-class std-class))
296 (set-slot 'direct-slots direct-slots)
297 (set-slot 'slots slots)
298 (set-slot 'initialize-info nil))
300 ;; For all direct superclasses SUPER of CLASS, make sure CLASS is
301 ;; a direct subclass of SUPER. Note that METACLASS-NAME doesn't
302 ;; matter here for the slot DIRECT-SUBCLASSES, since every class
303 ;; inherits the slot from class CLASS.
304 (dolist (super direct-supers)
305 (let* ((super (find-class super))
306 (subclasses (!bootstrap-get-slot metaclass-name super
307 'direct-subclasses)))
308 (cond ((eq +slot-unbound+ subclasses)
309 (!bootstrap-set-slot metaclass-name super 'direct-subclasses
311 ((not (memq class subclasses))
312 (!bootstrap-set-slot metaclass-name super 'direct-subclasses
313 (cons class subclasses))))))
315 (if (eq metaclass-name 'structure-class)
316 (let ((constructor-sym '|STRUCTURE-OBJECT class constructor|))
317 (set-slot 'predicate-name (or (cadr (assoc name
318 *early-class-predicates*))
319 (make-class-predicate-name name)))
320 (set-slot 'defstruct-form
321 `(defstruct (structure-object (:constructor
324 (set-slot 'defstruct-constructor constructor-sym)
325 (set-slot 'from-defclass-p t)
326 (set-slot 'plist nil)
327 (set-slot 'prototype (funcall constructor-sym)))
329 (if proto-p proto (allocate-standard-instance wrapper))))
332 (defun !bootstrap-make-slot-definitions (name class slots wrapper effective-p)
334 (mapcar (lambda (slot)
336 (!bootstrap-make-slot-definition
337 name class slot wrapper effective-p index))
340 (defun !bootstrap-make-slot-definition
341 (name class slot wrapper effective-p index)
342 (let* ((slotd-class-name (if effective-p
343 'standard-effective-slot-definition
344 'standard-direct-slot-definition))
345 (slotd (allocate-standard-instance wrapper))
346 (slot-name (getf slot :name)))
347 (flet ((get-val (name) (getf slot name))
349 (!bootstrap-set-slot slotd-class-name slotd name val)))
350 (set-val 'name slot-name)
351 (set-val 'initform (get-val :initform))
352 (set-val 'initfunction (get-val :initfunction))
353 (set-val 'initargs (get-val :initargs))
354 (set-val 'readers (get-val :readers))
355 (set-val 'writers (get-val :writers))
356 (set-val 'allocation :instance)
357 (set-val 'type (or (get-val :type) t))
358 (set-val 'documentation (or (get-val :documentation) ""))
359 (set-val 'class class)
361 (set-val 'location index)
363 (set-val 'reader-function (make-optimized-std-reader-method-function
364 fsc-p slot-name index))
365 (set-val 'writer-function (make-optimized-std-writer-method-function
366 fsc-p slot-name index))
367 (set-val 'boundp-function (make-optimized-std-boundp-method-function
368 fsc-p slot-name index)))
369 (set-val 'accessor-flags 7)
370 (let ((table (or (gethash slot-name *name->class->slotd-table*)
371 (setf (gethash slot-name *name->class->slotd-table*)
372 (make-hash-table :test 'eq :size 5)))))
373 (setf (gethash class table) slotd)))
374 (when (and (eq name 'standard-class)
375 (eq slot-name 'slots) effective-p)
376 (setq *the-eslotd-standard-class-slots* slotd))
377 (when (and (eq name 'funcallable-standard-class)
378 (eq slot-name 'slots) effective-p)
379 (setq *the-eslotd-funcallable-standard-class-slots* slotd))
382 (defun !bootstrap-accessor-definitions (early-p)
383 (let ((*early-p* early-p))
384 (dolist (definition *early-class-definitions*)
385 (let ((name (ecd-class-name definition))
386 (meta (ecd-metaclass definition)))
387 (unless (eq meta 'built-in-class)
388 (let ((direct-slots (ecd-canonical-slots definition)))
389 (dolist (slotd direct-slots)
390 (let ((slot-name (getf slotd :name))
391 (readers (getf slotd :readers))
392 (writers (getf slotd :writers)))
393 (!bootstrap-accessor-definitions1
399 (!bootstrap-accessor-definitions1
402 (list (slot-reader-name slot-name))
403 (list (slot-writer-name slot-name))
404 (list (slot-boundp-name slot-name)))))))))))
406 (defun !bootstrap-accessor-definition (class-name accessor-name slot-name type)
407 (multiple-value-bind (accessor-class make-method-function arglist specls doc)
409 (reader (values 'standard-reader-method
410 #'make-std-reader-method-function
413 "automatically generated reader method"))
414 (writer (values 'standard-writer-method
415 #'make-std-writer-method-function
416 (list 'new-value class-name)
418 "automatically generated writer method"))
419 (boundp (values 'standard-boundp-method
420 #'make-std-boundp-method-function
423 "automatically generated boundp method")))
424 (let ((gf (ensure-generic-function accessor-name)))
425 (if (find specls (early-gf-methods gf)
426 :key #'early-method-specializers
428 (unless (assoc accessor-name *!generic-function-fixups*
432 (make-a-method accessor-class
435 (funcall make-method-function
436 class-name slot-name)
440 (defun !bootstrap-accessor-definitions1 (class-name
445 (flet ((do-reader-definition (reader)
446 (!bootstrap-accessor-definition class-name
450 (do-writer-definition (writer)
451 (!bootstrap-accessor-definition class-name
455 (do-boundp-definition (boundp)
456 (!bootstrap-accessor-definition class-name
460 (dolist (reader readers) (do-reader-definition reader))
461 (dolist (writer writers) (do-writer-definition writer))
462 (dolist (boundp boundps) (do-boundp-definition boundp))))
464 (defun !bootstrap-class-predicates (early-p)
465 (let ((*early-p* early-p))
466 (dolist (definition *early-class-definitions*)
467 (let* ((name (ecd-class-name definition))
468 (class (find-class name)))
469 (setf (find-class-predicate name)
470 (make-class-predicate class (class-predicate-name class)))))))
472 (defun !bootstrap-built-in-classes ()
474 ;; First make sure that all the supers listed in
475 ;; *BUILT-IN-CLASS-LATTICE* are themselves defined by
476 ;; *BUILT-IN-CLASS-LATTICE*. This is just to check for typos and
477 ;; other sorts of brainos.
478 (dolist (e *built-in-classes*)
479 (dolist (super (cadr e))
480 (unless (or (eq super t)
481 (assq super *built-in-classes*))
482 (error "in *BUILT-IN-CLASSES*: ~S has ~S as a super,~%~
483 but ~S is not itself a class in *BUILT-IN-CLASSES*."
484 (car e) super super))))
486 ;; In the first pass, we create a skeletal object to be bound to the
488 (let* ((built-in-class (find-class 'built-in-class))
489 (built-in-class-wrapper (class-wrapper built-in-class)))
490 (dolist (e *built-in-classes*)
491 (let ((class (allocate-standard-instance built-in-class-wrapper)))
492 (setf (find-class (car e)) class))))
494 ;; In the second pass, we initialize the class objects.
495 (let ((class-eq-wrapper (class-wrapper (find-class 'class-eq-specializer))))
496 (dolist (e *built-in-classes*)
497 (destructuring-bind (name supers subs cpl prototype) e
498 (let* ((class (find-class name))
499 (lclass (find-classoid name))
500 (wrapper (classoid-layout lclass)))
501 (set (get-built-in-class-symbol name) class)
502 (set (get-built-in-wrapper-symbol name) wrapper)
503 (setf (classoid-pcl-class lclass) class)
505 (!bootstrap-initialize-class 'built-in-class class
506 name class-eq-wrapper nil
509 wrapper prototype)))))
511 (dolist (e *built-in-classes*)
512 (let* ((name (car e))
513 (class (find-class name)))
514 (setf (find-class-predicate name)
515 (make-class-predicate class (class-predicate-name class))))))
517 (defmacro wrapper-of-macro (x)
521 (wrapper-class* (wrapper-of-macro x)))
523 ;;; FIXME: We probably don't need both WRAPPER-OF and WRAPPER-OF-MACRO.
524 #-sb-fluid (declaim (inline wrapper-of))
525 (defun wrapper-of (x)
526 (wrapper-of-macro x))
528 (defun eval-form (form)
529 (lambda () (eval form)))
531 (defun ensure-non-standard-class (name &optional existing-class)
533 ((ensure (metaclass &optional (slots nil slotsp))
535 (mapcar #'classoid-name (classoid-direct-superclasses
536 (find-classoid name)))))
538 (ensure-class-using-class existing-class name
539 :metaclass metaclass :name name
540 :direct-superclasses supers
542 (ensure-class-using-class existing-class name
543 :metaclass metaclass :name name
544 :direct-superclasses supers))))
545 (slot-initargs-from-structure-slotd (slotd)
546 (let ((accessor (structure-slotd-accessor-symbol slotd)))
547 `(:name ,(structure-slotd-name slotd)
548 :defstruct-accessor-symbol ,accessor
549 ,@(when (fboundp accessor)
550 `(:internal-reader-function
551 ,(structure-slotd-reader-function slotd)
552 :internal-writer-function
553 ,(structure-slotd-writer-function slotd)))
554 :type ,(or (structure-slotd-type slotd) t)
555 :initform ,(structure-slotd-init-form slotd)
556 :initfunction ,(eval-form (structure-slotd-init-form slotd))))))
557 (cond ((structure-type-p name)
558 (ensure 'structure-class
559 (mapcar #'slot-initargs-from-structure-slotd
560 (structure-type-slot-description-list name))))
561 ((condition-type-p name)
562 (ensure 'condition-class))
564 (error "~@<~S is not the name of a class.~@:>" name)))))
566 (defun maybe-reinitialize-structure-class (classoid)
567 (let ((class (classoid-pcl-class classoid)))
569 (ensure-non-standard-class (class-name class) class))))
571 (pushnew 'maybe-reinitialize-structure-class sb-kernel::*defstruct-hooks*)
573 (defun make-class-predicate (class name)
574 (let* ((gf (ensure-generic-function name))
575 (mlist (if (eq *boot-state* 'complete)
576 (generic-function-methods gf)
577 (early-gf-methods gf))))
579 (unless (eq class *the-class-t*)
580 (let* ((default-method-function #'constantly-nil)
581 (default-method-initargs (list :function
582 default-method-function))
583 (default-method (make-a-method
588 default-method-initargs
589 "class predicate default method")))
590 (setf (method-function-get default-method-function :constant-value)
592 (add-method gf default-method)))
593 (let* ((class-method-function #'constantly-t)
594 (class-method-initargs (list :function
595 class-method-function))
596 (class-method (make-a-method 'standard-method
600 class-method-initargs
601 "class predicate class method")))
602 (setf (method-function-get class-method-function :constant-value) t)
603 (add-method gf class-method)))
606 ;;; Set the inherits from CPL, and register the layout. This actually
607 ;;; installs the class in the Lisp type system.
608 (defun update-lisp-class-layout (class layout)
609 (let ((lclass (layout-classoid layout)))
610 (unless (eq (classoid-layout lclass) layout)
611 (setf (layout-inherits layout)
612 (order-layout-inherits
613 (map 'simple-vector #'class-wrapper
614 (reverse (rest (class-precedence-list class))))))
615 (register-layout layout :invalidate t)
617 ;; Subclasses of formerly forward-referenced-class may be
618 ;; unknown to CL:FIND-CLASS and also anonymous. This
619 ;; functionality moved here from (SETF FIND-CLASS).
620 (let ((name (class-name class)))
621 (setf (find-classoid name) lclass
622 (classoid-name lclass) name)))))
624 (defun set-class-type-translation (class name)
625 (let ((classoid (find-classoid name nil)))
629 (let ((translation (built-in-classoid-translation classoid)))
632 (aver (ctype-p translation))
633 (setf (info :type :translator class)
634 (lambda (spec) (declare (ignore spec)) translation)))
636 (setf (info :type :translator class)
637 (lambda (spec) (declare (ignore spec)) classoid))))))
639 (setf (info :type :translator class)
640 (lambda (spec) (declare (ignore spec)) classoid))))))
642 (clrhash *find-class*)
643 (!bootstrap-meta-braid)
644 (!bootstrap-accessor-definitions t)
645 (!bootstrap-class-predicates t)
646 (!bootstrap-accessor-definitions nil)
647 (!bootstrap-class-predicates nil)
648 (!bootstrap-built-in-classes)
650 (dohash (name x *find-class*)
651 (let* ((class (find-class-from-cell name x))
652 (layout (class-wrapper class))
653 (lclass (layout-classoid layout))
654 (lclass-pcl-class (classoid-pcl-class lclass))
655 (olclass (find-classoid name nil)))
657 (aver (eq class lclass-pcl-class))
658 (setf (classoid-pcl-class lclass) class))
660 (update-lisp-class-layout class layout)
663 (aver (eq lclass olclass)))
665 (setf (find-classoid name) lclass)))
667 (set-class-type-translation class name)))
669 (setq *boot-state* 'braid)
671 (defmethod no-applicable-method (generic-function &rest args)
672 (error "~@<There is no matching method for the generic function ~2I~_~S~
673 ~I~_when called with arguments ~2I~_~S.~:>"
677 (defmethod no-next-method ((generic-function standard-generic-function)
678 (method standard-method) &rest args)
679 (error "~@<There is no next method for the generic function ~2I~_~S~
680 ~I~_when called from method ~2I~_~S~I~_with arguments ~2I~_~S.~:>"
685 ;;; An extension to the ANSI standard: in the presence of e.g. a
686 ;;; :BEFORE method, it would seem that going through
687 ;;; NO-APPLICABLE-METHOD is prohibited, as in fact there is an
688 ;;; applicable method. -- CSR, 2002-11-15
689 (defmethod no-primary-method (generic-function &rest args)
690 (error "~@<There is no primary method for the generic function ~2I~_~S~
691 ~I~_when called with arguments ~2I~_~S.~:>"