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1 ;;; eieio.el --- Enhanced Implementation of Emacs Interpreted Objects -*- lexical-binding:t -*-
2 ;;; or maybe Eric's Implementation of Emacs Interpreted Objects
4 ;; Copyright (C) 1995-1996, 1998-2017 Free Software Foundation, Inc.
6 ;; Author: Eric M. Ludlam <zappo@gnu.org>
7 ;; Version: 1.4
8 ;; Keywords: OO, lisp
10 ;; This file is part of GNU Emacs.
12 ;; GNU Emacs is free software: you can redistribute it and/or modify
13 ;; it under the terms of the GNU General Public License as published by
14 ;; the Free Software Foundation, either version 3 of the License, or
15 ;; (at your option) any later version.
17 ;; GNU Emacs is distributed in the hope that it will be useful,
18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 ;; GNU General Public License for more details.
22 ;; You should have received a copy of the GNU General Public License
23 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
25 ;;; Commentary:
26 ;;
27 ;; EIEIO is a series of Lisp routines which implements a subset of
28 ;; CLOS, the Common Lisp Object System. In addition, EIEIO also adds
29 ;; a few new features which help it integrate more strongly with the
30 ;; Emacs running environment.
31 ;;
32 ;; See eieio.texi for complete documentation on using this package.
33 ;;
34 ;; Note: the implementation of the c3 algorithm is based on:
35 ;; Kim Barrett et al.: A Monotonic Superclass Linearization for Dylan
36 ;; Retrieved from:
37 ;; http://192.220.96.201/dylan/linearization-oopsla96.html
39 ;; @TODO - fix :initform to be a form, not a quoted value
40 ;; @TODO - Prefix non-clos functions with `eieio-'.
42 ;; TODO: better integrate CL's defstructs and classes. E.g. make it possible
43 ;; to create a new class that inherits from a struct.
45 ;;; Code:
51 "Display the current version of EIEIO."
57 \f
58 ;;; Defining a new class
59 ;;
61 "Define NAME as a new class derived from SUPERCLASS with SLOTS.
62 OPTIONS-AND-DOC is used as the class' options and base documentation.
63 SUPERCLASSES is a list of superclasses to inherit from, with SLOTS
64 being the slots residing in that class definition. Supported tags are:
66 :initform - Initializing form.
67 :initarg - Tag used during initialization.
68 :accessor - Tag used to create a function to access this slot.
69 :allocation - Specify where the value is stored.
70 Defaults to `:instance', but could also be `:class'.
71 :writer - A function symbol which will `write' an object's slot.
72 :reader - A function symbol which will `read' an object.
73 :type - The type of data allowed in this slot (see `typep').
74 :documentation
75 - A string documenting use of this slot.
77 The following are extensions on CLOS:
78 :custom - When customizing an object, the custom :type. Public only.
79 :label - A text string label used for a slot when customizing.
80 :group - Name of a customization group this slot belongs in.
81 :printer - A function to call to print the value of a slot.
82 See `eieio-override-prin1' as an example.
84 A class can also have optional options. These options happen in place
85 of documentation (including a :documentation tag), in addition to
86 documentation, or not at all. Supported options are:
88 :documentation - The doc-string used for this class.
90 Options added to EIEIO:
92 :allow-nil-initform - Non-nil to skip typechecking of null initforms.
93 :custom-groups - List of custom group names. Organizes slots into
94 reasonable groups for customizations.
95 :abstract - Non-nil to prevent instances of this class.
96 If a string, use as an error string if someone does
97 try to make an instance.
98 :method-invocation-order
99 - Control the method invocation order if there is
100 multiple inheritance. Valid values are:
101 :breadth-first - The default.
102 :depth-first
104 Options in CLOS not supported in EIEIO:
106 :metaclass - Class to use in place of `standard-class'
107 :default-initargs - Initargs to use when initializing new objects of
108 this class.
110 Due to the way class options are set up, you can add any tags you wish,
111 and reference them using the function `class-option'."
126 ;; Make sure the method invocation order is a valid value.
136 ;; Collect the accessors we need to define.
145 ;; Update eieio--known-slot-names already in case we compile code which
146 ;; uses this before the class is loaded.
153 :initform
154 :initarg
155 :documentation
156 :protection
157 :reader
158 :writer
159 :allocation
160 :type
161 :custom
162 :label
163 :group
164 :printer
165 :allow-nil-initform
170 ;; Make sure the :allocation parameter has a valid value.
174 ;; Label is nil, or a string
178 ;; Is there an initarg, but allocation of class?
182 ;; Anyone can have an accessor function. This creates a function
183 ;; of the specified name, and also performs a `defsetf' if applicable
184 ;; so that users can `setf' the space returned by this function.
188 accessors)
191 "Retrieve the slot `%S' from an object of class `%S'."
192 sname name)
193 ;; FIXME: Why is this different from the :reader case?
195 accessors)
197 ;; FIXME: How could I declare this *method* as obsolete.
200 "Retrieve the class slot `%S' from a class `%S'.
201 This method is obsolete."
202 sname name)
205 accessors)))
207 ;; If a writer is defined, then create a generic method of that
208 ;; name whose purpose is to set the value of the slot.
212 sname name)
214 accessors))
215 ;; If a reader is defined, then create a generic method
216 ;; of that name whose purpose is to access this slot value.
220 sname name)
222 accessors))
223 ))
226 ;; This test must be created right away so we can have self-
227 ;; referencing classes. ei, a class whose slot can contain only
228 ;; pointers to itself.
230 ;; Create the test functions.
241 ;; When using typep, (typep OBJ 'myclass) returns t for objects which
242 ;; are subclasses of myclass. For our predicates, however, it is
243 ;; important for EIEIO to be backwards compatible, where
244 ;; myobject-p, and myobject-child-p are different.
245 ;; "cl" uses this technique to specify symbols with specific typep
246 ;; test, so we can let typep have the CLOS documented behavior
247 ;; while keeping our above predicate clean.
253 ,@accessors
255 ;; Create the constructor function
257 ;; Abstract classes cannot be instantiated. Say so.
265 ;; Non-abstract classes need a constructor.
271 whole
275 ;; Keep the name arg, for backward compatibility,
276 ;; but hide it so we don't trigger indefinitely.
282 ;;; Get/Set slots in an object.
283 ;;
285 "Retrieve the value stored in OBJ in the slot named by SLOT.
286 Slot is the name of the slot when created by `defclass' or the label
287 created by the :initarg tag."
296 "Get the default value of OBJ (maybe a class) for SLOT.
297 The default value is the value installed in a class with the :initform
298 tag. SLOT can be the slot name, or the tag specified by the :initarg
299 tag in the `defclass' call."
303 ;;; Handy CLOS macros
304 ;;
306 "Bind SPEC-LIST lexically to slot values in OBJECT, and execute BODY.
307 This establishes a lexical environment for referring to the slots in
308 the instance named by the given slot-names as though they were
309 variables. Within such a context the value of the slot can be
310 specified by using its slot name, as if it were a lexically bound
311 variable. Both setf and setq can be used to set the value of the
312 slot.
314 SPEC-LIST is of a form similar to `let'. For example:
316 ((VAR1 SLOT1)
317 SLOT2
318 SLOTN
319 (VARN+1 SLOTN+1))
321 Where each VAR is the local variable given to the associated
322 SLOT. A slot specified without a variable name is given a
323 variable name of the same name as the slot."
326 ;; Transform the spec-list into a cl-symbol-macrolet spec-list.
333 spec-list)
336 ;; Keep it as a non-inlined function, so the internals of object don't get
337 ;; hard-coded in random .elc files.
339 "Return some data structure from which can be extracted the slot offset."
343 "Find the index to pass to `aref' to access SLOT."
346 index))))
349 "Pcase patterns to match EIEIO objects.
350 Elements of FIELDS can be of the form (NAME PAT) in which case the contents of
351 field NAME is matched against PAT, or they can be of the form NAME which
352 is a shorthand for (NAME NAME)."
355 ;; FIXME: This generates a horrendous mess of redundant let bindings.
356 ;; `pcase' needs to be improved somehow to introduce let-bindings more
357 ;; sparingly, or the byte-compiler needs to be taught to optimize
358 ;; them away.
359 ;; FIXME: `pcase' does not do a good job here of sharing tests&code among
360 ;; various branches.
371 fields))))
372 \f
373 ;;; Simple generators, and query functions. None of these would do
374 ;; well embedded into an object.
375 ;;
381 "Return a string which is OBJ's name."
385 "Return a printed representation for object OBJ.
386 If EXTRA, include that in the string returned to represent the symbol."
394 ;; In the past, every EIEIO object had a `name' field, so we had the two method
395 ;; below "for free". Since this field is very rarely used, we got rid of it
396 ;; and instead we keep it in a weak hash-tables, for those very rare objects
397 ;; that use it.
405 "Set the string which is OBJ's NAME."
413 "Return the class struct defining OBJ."
414 ;; FIXME: We say we return a "struct" but we return a symbol instead!
418 ;; CLOS name, maybe?
422 "Return a Lisp like symbol name for OBJ's class."
429 "Return parent classes to CLASS. (overload of variable).
431 The CLOS function `class-direct-superclasses' is aliased to this function."
437 "Return child classes to CLASS.
438 The CLOS function `class-direct-subclasses' is aliased to this function."
444 ;; Official CLOS functions.
451 "Return first parent class to CLASS. (overload of variable)."
456 "Return t if OBJ is of class-type CLASS."
463 "Return non-nil if OBJ is an instance of CLASS or CLASS' subclasses."
465 ;; class will be checked one layer down
467 ;; Backwards compatibility
471 "Return non-nil if CHILD class is a subclass of CLASS."
474 ;; `eieio-default-superclass' is never mentioned in eieio--class-parents,
475 ;; so we have to special case it here.
489 "Return list of slots available in instances of CLASS."
490 ;; FIXME: This only gives the instance slots and ignores the
491 ;; class-allocated slots.
497 "Return list of slot names available in OBJ."
504 "Fetch from CLASS, SLOT's :initarg."
512 f))
514 ;;; Object Set macros
515 ;;
517 "Set the value in OBJ for slot SLOT to VALUE.
518 SLOT is the slot name as specified in `defclass' or the tag created
519 with in the :initarg slot. VALUE can be any Lisp object."
524 "Set the default slot in CLASS for SLOT to VALUE.
525 The default value is usually set with the :initform tag during class
526 creation. This allows users to change the default behavior of classes
527 after they are created."
531 ;;; CLOS queries into classes and slots
532 ;;
534 "Return non-nil if OBJECT's SLOT is bound.
535 Setting a slot's value makes it bound. Calling `slot-makeunbound' will
536 make a slot unbound.
537 OBJECT can be an instance or a class."
538 ;; Skip typechecking while retrieving this value.
540 ;; Return nil if the magic symbol is in there.
545 eieio-unbound))))
548 "In OBJECT, make SLOT unbound."
552 "Return non-nil if OBJECT-OR-CLASS has SLOT."
558 ;; FIXME: We could speed this up by adding class slots into the
559 ;; index-table (e.g. with a negative index?).
561 found)
565 found))))
568 "Return the class that SYMBOL represents.
569 If there is no class, nil is returned if ERRORP is nil.
570 If ERRORP is non-nil, `wrong-argument-type' is signaled."
576 ;;; Slightly more complex utility functions for objects
577 ;;
579 "Return an object if KEY is `equal' to SLOT's value of an object in LIST.
580 LIST is a list of objects whose slots are searched.
581 Objects in LIST do not need to have a slot named SLOT, nor does
582 SLOT need to be bound. If these errors occur, those objects will
583 be ignored."
586 ;; This prevents errors for missing slots.
593 "Return an association list with the contents of SLOT as the key element.
594 LIST must be a list of objects with SLOT in it.
595 This is useful when you need to do completing read on an object group."
601 assoclist))
606 "Return an association list with the contents of SLOT as the key element.
607 LIST must be a list of objects, but those objects do not need to have
608 SLOT in it. If it does not, then that element is left out of the association
609 list."
616 assoclist)))
621 "In OBJECT's SLOT, add ITEM to the list of elements.
622 Optional argument APPEND indicates we need to append to the list.
623 If ITEM already exists in the list in SLOT, then it is not added.
624 Comparison is done with `equal' through the `member' function call.
625 If SLOT is unbound, bind it to the list containing ITEM."
627 ;; Find the originating list.
631 ;; turn it into a list.
634 ;; Do the combination
640 ;; Set back into the slot.
644 "In OBJECT's SLOT, remove occurrences of ITEM.
645 Deletion is done with `delete', which deletes by side effect,
646 and comparisons are done with `equal'.
647 If SLOT is unbound, do nothing."
649 nil
652 ;;; Here are some CLOS items that need the CL package
653 ;;
655 ;; FIXME: Shouldn't this be a more complex gv-expander which extracts the
656 ;; common code between oref and oset, so as to reduce the redundant work done
657 ;; in (push foo (oref bar baz)), like we do for the `nth' expander?
660 \f
661 ;;;
662 ;; We want all objects created by EIEIO to have some default set of
663 ;; behaviors so we can create object utilities, and allow various
664 ;; types of error checking. To do this, create the default EIEIO
665 ;; class, and when no parent class is specified, use this as the
666 ;; default. (But don't store it in the other classes as the default,
667 ;; allowing for transparent support.)
668 ;;
671 nil
672 "Default parent class for classes with no specified parent class.
673 Its slots are automatically adopted by classes with no specified parents.
674 This class is not stored in the `parent' slot of a class vector."
683 "Make a new instance of CLASS based on INITARGS.
684 For example:
688 INITARGS is a property list with keywords based on the `:initarg'
689 for each slot. For example:
697 "Default constructor for CLASS `eieio-default-superclass'.
698 SLOTS are the initialization slots used by `initialize-instance'.
699 This static method is called when an object is constructed.
700 It allocates the vector used to represent an EIEIO object, and then
701 calls `initialize-instance' on that object."
708 "Obsolete name %S passed to %S constructor"
710 ;; Call the initialize method on the new object with the slots
711 ;; that were passed down to us.
713 ;; Return the created object.
714 new-object))
716 ;; FIXME: CLOS uses "&rest INITARGS" instead.
718 "Set slots of OBJ with SLOTS which is a list of name/value pairs.
722 "Set slots of OBJ with SLOTS which is a list of name/value pairs.
723 Called from the constructor routine."
732 ;; FIXME: CLOS uses "&rest INITARGS" instead.
738 "Construct the new object THIS based on SLOTS.
739 SLOTS is a tagged list where odd numbered elements are tags, and
740 even numbered elements are the values to store in the tagged slot.
741 If you overload the `initialize-instance', there you will need to
742 call `shared-initialize' yourself, or you can call `call-next-method'
743 to have this constructor called automatically. If these steps are
744 not taken, then new objects of your class will not have their values
745 dynamically set from SLOTS."
746 ;; First, see if any of our defaults are `lambda', and
747 ;; re-evaluate them and apply the value to our slots.
751 ;; For each slot, see if we need to evaluate it.
752 ;;
753 ;; Paul Landes said in an email:
754 ;; > CL evaluates it if it can, and otherwise, leaves it as
755 ;; > the quoted thing as you already have. This is by the
756 ;; > Sonya E. Keene book and other things I've look at on the
757 ;; > web.
762 ;; FIXME: We should be able to just do (aset this (+ i <cst>) dflt)!
764 ;; Shared initialize will parse our slots for us.
768 "Method invoked when an attempt to access a slot in OBJECT fails.
769 SLOT-NAME is the name of the failed slot, OPERATION is the type of access
770 that was requested, and optional NEW-VALUE is the value that was desired
771 to be set.
773 This method is called from `oref', `oset', and other functions which
774 directly reference slots in EIEIO objects."
777 slot-name)))
783 class slot-name fn)
784 "Slot unbound is invoked during an attempt to reference an unbound slot.
785 OBJECT is the instance of the object being reference. CLASS is the
786 class of OBJECT, and SLOT-NAME is the offending slot. This function
787 throws the signal `unbound-slot'. You can overload this function and
788 return the value to use in place of the unbound value.
789 Argument FN is the function signaling this error.
790 Use `slot-boundp' to determine if a slot is bound or not.
792 In CLOS, the argument list is (CLASS OBJECT SLOT-NAME), but
793 EIEIO can only dispatch on the first argument, so the first two are swapped."
796 slot-name fn)))
799 "Make a copy of OBJ, and then supply PARAMS.
800 PARAMS is a parameter list of the same form used by `initialize-instance'.
802 When overloading `clone', be sure to call `call-next-method'
806 "Make a copy of OBJ, and then apply PARAMS."
812 nobj))
815 "Destructor for cleaning up any dynamic links to our object."
817 ;; No cleanup... yet.
818 nil)
821 "Pretty printer for object THIS.
823 It is sometimes useful to put a summary of the object into the
824 default #<notation> string when using EIEIO browsing tools.
825 Implement this method to customize the summary."
830 "Pretty printer for object THIS. Call function `object-name' with STRINGS.
831 The default method for printing object THIS is to use the
832 function `object-name'.
834 It is sometimes useful to put a summary of the object into the
835 default #<notation> string when using EIEIO browsing tools.
837 Implement this function and specify STRINGS in a call to
838 `call-next-method' to provide additional summary information.
839 When passing in extra strings from child classes, always remember
840 to prepend a space."
845 "Default printer for EIEIO objects."
846 ;; Fallback to the old `object-print'.
853 "Write out object THIS to the current stream.
857 "Write object THIS out to the current stream.
858 This writes out the vector version of this object. Complex and recursive
859 object are discouraged from being written.
860 If optional COMMENT is non-nil, include comments when outputting
861 this object."
870 ;; Now output readable lisp to recreate this object
871 ;; It should look like this:
872 ;; (<constructor> <name> <slot> <slot> ... )
873 ;; Each slot's slot is writen using its :writer.
880 ;; Loop over all the public slots
895 ;; Use our public printer
900 v))
901 ;; Use our generic override prin1 function.
911 "Perform a `prin1' on THING taking advantage of object knowledge."
921 "Display LIST where list may contain objects."
938 \f
939 ;;; Unimplemented functions from CLOS
940 ;;
942 "Change the class of OBJ to type CLASS.
943 This may create or delete slots, but does not affect the return value
944 of `eq'."
948 ;; Hook ourselves into help system for describing classes and methods.
949 ;; FIXME: This is not actually needed any more since we can click on the
950 ;; hyperlink from the constructor's docstring to see the type definition.
955 ;;; eieio ends here