1 This is ../info/lispref.info, produced by makeinfo version 4.0 from
4 INFO-DIR-SECTION XEmacs Editor
6 * Lispref: (lispref). XEmacs Lisp Reference Manual.
11 GNU Emacs Lisp Reference Manual Second Edition (v2.01), May 1993 GNU
12 Emacs Lisp Reference Manual Further Revised (v2.02), August 1993 Lucid
13 Emacs Lisp Reference Manual (for 19.10) First Edition, March 1994
14 XEmacs Lisp Programmer's Manual (for 19.12) Second Edition, April 1995
15 GNU Emacs Lisp Reference Manual v2.4, June 1995 XEmacs Lisp
16 Programmer's Manual (for 19.13) Third Edition, July 1995 XEmacs Lisp
17 Reference Manual (for 19.14 and 20.0) v3.1, March 1996 XEmacs Lisp
18 Reference Manual (for 19.15 and 20.1, 20.2, 20.3) v3.2, April, May,
19 November 1997 XEmacs Lisp Reference Manual (for 21.0) v3.3, April 1998
21 Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Free Software
22 Foundation, Inc. Copyright (C) 1994, 1995 Sun Microsystems, Inc.
23 Copyright (C) 1995, 1996 Ben Wing.
25 Permission is granted to make and distribute verbatim copies of this
26 manual provided the copyright notice and this permission notice are
27 preserved on all copies.
29 Permission is granted to copy and distribute modified versions of
30 this manual under the conditions for verbatim copying, provided that the
31 entire resulting derived work is distributed under the terms of a
32 permission notice identical to this one.
34 Permission is granted to copy and distribute translations of this
35 manual into another language, under the above conditions for modified
36 versions, except that this permission notice may be stated in a
37 translation approved by the Foundation.
39 Permission is granted to copy and distribute modified versions of
40 this manual under the conditions for verbatim copying, provided also
41 that the section entitled "GNU General Public License" is included
42 exactly as in the original, and provided that the entire resulting
43 derived work is distributed under the terms of a permission notice
44 identical to this one.
46 Permission is granted to copy and distribute translations of this
47 manual into another language, under the above conditions for modified
48 versions, except that the section entitled "GNU General Public License"
49 may be included in a translation approved by the Free Software
50 Foundation instead of in the original English.
53 File: lispref.info, Node: Copying, Next: Introduction, Prev: Top, Up: Top
55 GNU GENERAL PUBLIC LICENSE
56 **************************
60 Copyright (C) 1989, 1991 Free Software Foundation, Inc.
61 675 Mass Ave, Cambridge, MA 02139, USA
63 Everyone is permitted to copy and distribute verbatim copies
64 of this license document, but changing it is not allowed.
69 The licenses for most software are designed to take away your
70 freedom to share and change it. By contrast, the GNU General Public
71 License is intended to guarantee your freedom to share and change free
72 software--to make sure the software is free for all its users. This
73 General Public License applies to most of the Free Software
74 Foundation's software and to any other program whose authors commit to
75 using it. (Some other Free Software Foundation software is covered by
76 the GNU Library General Public License instead.) You can apply it to
79 When we speak of free software, we are referring to freedom, not
80 price. Our General Public Licenses are designed to make sure that you
81 have the freedom to distribute copies of free software (and charge for
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83 if you want it, that you can change the software or use pieces of it in
84 new free programs; and that you know you can do these things.
86 To protect your rights, we need to make restrictions that forbid
87 anyone to deny you these rights or to ask you to surrender the rights.
88 These restrictions translate to certain responsibilities for you if you
89 distribute copies of the software, or if you modify it.
91 For example, if you distribute copies of such a program, whether
92 gratis or for a fee, you must give the recipients all the rights that
93 you have. You must make sure that they, too, receive or can get the
94 source code. And you must show them these terms so they know their
97 We protect your rights with two steps: (1) copyright the software,
98 and (2) offer you this license which gives you legal permission to copy,
99 distribute and/or modify the software.
101 Also, for each author's protection and ours, we want to make certain
102 that everyone understands that there is no warranty for this free
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114 The precise terms and conditions for copying, distribution and
117 TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
119 0. This License applies to any program or other work which contains a
120 notice placed by the copyright holder saying it may be distributed
121 under the terms of this General Public License. The "Program",
122 below, refers to any such program or work, and a "work based on
123 the Program" means either the Program or any derivative work under
124 copyright law: that is to say, a work containing the Program or a
125 portion of it, either verbatim or with modifications and/or
126 translated into another language. (Hereinafter, translation is
127 included without limitation in the term "modification".) Each
128 licensee is addressed as "you".
130 Activities other than copying, distribution and modification are
131 not covered by this License; they are outside its scope. The act
132 of running the Program is not restricted, and the output from the
133 Program is covered only if its contents constitute a work based on
134 the Program (independent of having been made by running the
135 Program). Whether that is true depends on what the Program does.
137 1. You may copy and distribute verbatim copies of the Program's
138 source code as you receive it, in any medium, provided that you
139 conspicuously and appropriately publish on each copy an appropriate
140 copyright notice and disclaimer of warranty; keep intact all the
141 notices that refer to this License and to the absence of any
142 warranty; and give any other recipients of the Program a copy of
143 this License along with the Program.
145 You may charge a fee for the physical act of transferring a copy,
146 and you may at your option offer warranty protection in exchange
149 2. You may modify your copy or copies of the Program or any portion
150 of it, thus forming a work based on the Program, and copy and
151 distribute such modifications or work under the terms of Section 1
152 above, provided that you also meet all of these conditions:
154 a. You must cause the modified files to carry prominent notices
155 stating that you changed the files and the date of any change.
157 b. You must cause any work that you distribute or publish, that
158 in whole or in part contains or is derived from the Program
159 or any part thereof, to be licensed as a whole at no charge
160 to all third parties under the terms of this License.
162 c. If the modified program normally reads commands interactively
163 when run, you must cause it, when started running for such
164 interactive use in the most ordinary way, to print or display
165 an announcement including an appropriate copyright notice and
166 a notice that there is no warranty (or else, saying that you
167 provide a warranty) and that users may redistribute the
168 program under these conditions, and telling the user how to
169 view a copy of this License. (Exception: if the Program
170 itself is interactive but does not normally print such an
171 announcement, your work based on the Program is not required
172 to print an announcement.)
174 These requirements apply to the modified work as a whole. If
175 identifiable sections of that work are not derived from the
176 Program, and can be reasonably considered independent and separate
177 works in themselves, then this License, and its terms, do not
178 apply to those sections when you distribute them as separate
179 works. But when you distribute the same sections as part of a
180 whole which is a work based on the Program, the distribution of
181 the whole must be on the terms of this License, whose permissions
182 for other licensees extend to the entire whole, and thus to each
183 and every part regardless of who wrote it.
185 Thus, it is not the intent of this section to claim rights or
186 contest your rights to work written entirely by you; rather, the
187 intent is to exercise the right to control the distribution of
188 derivative or collective works based on the Program.
190 In addition, mere aggregation of another work not based on the
191 Program with the Program (or with a work based on the Program) on
192 a volume of a storage or distribution medium does not bring the
193 other work under the scope of this License.
195 3. You may copy and distribute the Program (or a work based on it,
196 under Section 2) in object code or executable form under the terms
197 of Sections 1 and 2 above provided that you also do one of the
200 a. Accompany it with the complete corresponding machine-readable
201 source code, which must be distributed under the terms of
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203 software interchange; or,
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206 years, to give any third party, for a charge no more than your
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235 4. You may not copy, modify, sublicense, or distribute the Program
236 except as expressly provided under this License. Any attempt
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238 void, and will automatically terminate your rights under this
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240 from you under this License will not have their licenses
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256 further restrictions on the recipients' exercise of the rights
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260 7. If, as a consequence of a court judgment or allegation of patent
261 infringement or for any other reason (not limited to patent
262 issues), conditions are imposed on you (whether by court order,
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269 royalty-free redistribution of the Program by all those who
270 receive copies directly or indirectly through you, then the only
271 way you could satisfy both it and this License would be to refrain
272 entirely from distribution of the Program.
274 If any portion of this section is held invalid or unenforceable
275 under any particular circumstance, the balance of the section is
276 intended to apply and the section as a whole is intended to apply
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290 This section is intended to make thoroughly clear what is believed
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293 8. If the distribution and/or use of the Program is restricted in
294 certain countries either by patents or by copyrighted interfaces,
295 the original copyright holder who places the Program under this
296 License may add an explicit geographical distribution limitation
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299 License incorporates the limitation as if written in the body of
302 9. The Free Software Foundation may publish revised and/or new
303 versions of the General Public License from time to time. Such
304 new versions will be similar in spirit to the present version, but
305 may differ in detail to address new problems or concerns.
307 Each version is given a distinguishing version number. If the
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310 the terms and conditions either of that version or of any later
311 version published by the Free Software Foundation. If the Program
312 does not specify a version number of this License, you may choose
313 any version ever published by the Free Software Foundation.
315 10. If you wish to incorporate parts of the Program into other free
316 programs whose distribution conditions are different, write to the
317 author to ask for permission. For software which is copyrighted
318 by the Free Software Foundation, write to the Free Software
319 Foundation; we sometimes make exceptions for this. Our decision
320 will be guided by the two goals of preserving the free status of
321 all derivatives of our free software and of promoting the sharing
322 and reuse of software generally.
326 11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO
327 WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE
328 LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
329 HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT
330 WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT
331 NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
332 FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE
333 QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE
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335 SERVICING, REPAIR OR CORRECTION.
337 12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN
338 WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY
339 MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE
340 LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL,
341 INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR
342 INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
343 DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU
344 OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY
345 OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN
346 ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
348 END OF TERMS AND CONDITIONS
350 How to Apply These Terms to Your New Programs
351 =============================================
353 If you develop a new program, and you want it to be of the greatest
354 possible use to the public, the best way to achieve this is to make it
355 free software which everyone can redistribute and change under these
358 To do so, attach the following notices to the program. It is safest
359 to attach them to the start of each source file to most effectively
360 convey the exclusion of warranty; and each file should have at least
361 the "copyright" line and a pointer to where the full notice is found.
363 ONE LINE TO GIVE THE PROGRAM'S NAME AND AN IDEA OF WHAT IT DOES.
364 Copyright (C) 19YY NAME OF AUTHOR
366 This program is free software; you can redistribute it and/or
367 modify it under the terms of the GNU General Public License
368 as published by the Free Software Foundation; either version 2
369 of the License, or (at your option) any later version.
371 This program is distributed in the hope that it will be useful,
372 but WITHOUT ANY WARRANTY; without even the implied warranty of
373 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
374 GNU General Public License for more details.
376 You should have received a copy of the GNU General Public License
377 along with this program; if not, write to the Free Software
378 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
380 Also add information on how to contact you by electronic and paper
383 If the program is interactive, make it output a short notice like
384 this when it starts in an interactive mode:
386 Gnomovision version 69, Copyright (C) 19YY NAME OF AUTHOR
387 Gnomovision comes with ABSOLUTELY NO WARRANTY; for details
388 type `show w'. This is free software, and you are welcome
389 to redistribute it under certain conditions; type `show c'
392 The hypothetical commands `show w' and `show c' should show the
393 appropriate parts of the General Public License. Of course, the
394 commands you use may be called something other than `show w' and `show
395 c'; they could even be mouse-clicks or menu items--whatever suits your
398 You should also get your employer (if you work as a programmer) or
399 your school, if any, to sign a "copyright disclaimer" for the program,
400 if necessary. Here is a sample; alter the names:
402 Yoyodyne, Inc., hereby disclaims all copyright
403 interest in the program `Gnomovision'
404 (which makes passes at compilers) written
407 SIGNATURE OF TY COON, 1 April 1989
408 Ty Coon, President of Vice
410 This General Public License does not permit incorporating your
411 program into proprietary programs. If your program is a subroutine
412 library, you may consider it more useful to permit linking proprietary
413 applications with the library. If this is what you want to do, use the
414 GNU Library General Public License instead of this License.
417 File: lispref.info, Node: Introduction, Next: Lisp Data Types, Prev: Copying, Up: Top
422 Most of the XEmacs text editor is written in the programming
423 language called XEmacs Lisp. You can write new code in XEmacs Lisp and
424 install it as an extension to the editor. However, XEmacs Lisp is more
425 than a mere "extension language"; it is a full computer programming
426 language in its own right. You can use it as you would any other
427 programming language.
429 Because XEmacs Lisp is designed for use in an editor, it has special
430 features for scanning and parsing text as well as features for handling
431 files, buffers, displays, subprocesses, and so on. XEmacs Lisp is
432 closely integrated with the editing facilities; thus, editing commands
433 are functions that can also conveniently be called from Lisp programs,
434 and parameters for customization are ordinary Lisp variables.
436 This manual describes XEmacs Lisp, presuming considerable familiarity
437 with the use of XEmacs for editing. (See `The XEmacs Reference
438 Manual', for this basic information.) Generally speaking, the earlier
439 chapters describe features of XEmacs Lisp that have counterparts in many
440 programming languages, and later chapters describe features that are
441 peculiar to XEmacs Lisp or relate specifically to editing.
447 * Caveats:: Flaws and a request for help.
448 * Lisp History:: XEmacs Lisp is descended from Maclisp.
449 * Conventions:: How the manual is formatted.
450 * Acknowledgements:: The authors, editors, and sponsors of this manual.
453 File: lispref.info, Node: Caveats, Next: Lisp History, Up: Introduction
458 This manual has gone through numerous drafts. It is nearly complete
459 but not flawless. There are a few topics that are not covered, either
460 because we consider them secondary (such as most of the individual
461 modes) or because they are yet to be written. Because we are not able
462 to deal with them completely, we have left out several parts
465 The manual should be fully correct in what it does cover, and it is
466 therefore open to criticism on anything it says--from specific examples
467 and descriptive text, to the ordering of chapters and sections. If
468 something is confusing, or you find that you have to look at the sources
469 or experiment to learn something not covered in the manual, then perhaps
470 the manual should be fixed. Please let us know.
472 As you use this manual, we ask that you send corrections as soon as
473 you find them. If you think of a simple, real life example for a
474 function or group of functions, please make an effort to write it up
475 and send it in. Please reference any comments to the node name and
476 function or variable name, as appropriate. Also state the number of
477 the edition which you are criticizing.
479 This manual was originally written for FSF Emacs 19 and was updated
480 by Ben Wing (ben@xemacs.org) for Lucid Emacs 19.10 and later for XEmacs
481 19.12, 19.13, 19.14, and 20.0. It was further updated by the XEmacs
482 Development Team for 19.15 and 20.1. Please send comments and
483 corrections relating to XEmacs-specific portions of this manual to
486 or post to the newsgroup
492 File: lispref.info, Node: Lisp History, Next: Conventions, Prev: Caveats, Up: Introduction
497 Lisp (LISt Processing language) was first developed in the late
498 1950's at the Massachusetts Institute of Technology for research in
499 artificial intelligence. The great power of the Lisp language makes it
500 superior for other purposes as well, such as writing editing commands.
502 Dozens of Lisp implementations have been built over the years, each
503 with its own idiosyncrasies. Many of them were inspired by Maclisp,
504 which was written in the 1960's at MIT's Project MAC. Eventually the
505 implementors of the descendants of Maclisp came together and developed a
506 standard for Lisp systems, called Common Lisp.
508 XEmacs Lisp is largely inspired by Maclisp, and a little by Common
509 Lisp. If you know Common Lisp, you will notice many similarities.
510 However, many of the features of Common Lisp have been omitted or
511 simplified in order to reduce the memory requirements of XEmacs.
512 Sometimes the simplifications are so drastic that a Common Lisp user
513 might be very confused. We will occasionally point out how XEmacs Lisp
514 differs from Common Lisp. If you don't know Common Lisp, don't worry
515 about it; this manual is self-contained.
518 File: lispref.info, Node: Conventions, Next: Acknowledgements, Prev: Lisp History, Up: Introduction
523 This section explains the notational conventions that are used in
524 this manual. You may want to skip this section and refer back to it
529 * Some Terms:: Explanation of terms we use in this manual.
530 * nil and t:: How the symbols `nil' and `t' are used.
531 * Evaluation Notation:: The format we use for examples of evaluation.
532 * Printing Notation:: The format we use for examples that print output.
533 * Error Messages:: The format we use for examples of errors.
534 * Buffer Text Notation:: The format we use for buffer contents in examples.
535 * Format of Descriptions:: Notation for describing functions, variables, etc.
538 File: lispref.info, Node: Some Terms, Next: nil and t, Up: Conventions
543 Throughout this manual, the phrases "the Lisp reader" and "the Lisp
544 printer" are used to refer to those routines in Lisp that convert
545 textual representations of Lisp objects into actual Lisp objects, and
546 vice versa. *Note Printed Representation::, for more details. You, the
547 person reading this manual, are thought of as "the programmer" and are
548 addressed as "you". "The user" is the person who uses Lisp programs,
549 including those you write.
551 Examples of Lisp code appear in this font or form: `(list 1 2 3)'.
552 Names that represent arguments or metasyntactic variables appear in
553 this font or form: FIRST-NUMBER.
556 File: lispref.info, Node: nil and t, Next: Evaluation Notation, Prev: Some Terms, Up: Conventions
561 In Lisp, the symbol `nil' has three separate meanings: it is a
562 symbol with the name `nil'; it is the logical truth value FALSE; and it
563 is the empty list--the list of zero elements. When used as a variable,
564 `nil' always has the value `nil'.
566 As far as the Lisp reader is concerned, `()' and `nil' are
567 identical: they stand for the same object, the symbol `nil'. The
568 different ways of writing the symbol are intended entirely for human
569 readers. After the Lisp reader has read either `()' or `nil', there is
570 no way to determine which representation was actually written by the
573 In this manual, we use `()' when we wish to emphasize that it means
574 the empty list, and we use `nil' when we wish to emphasize that it
575 means the truth value FALSE. That is a good convention to use in Lisp
578 (cons 'foo ()) ; Emphasize the empty list
579 (not nil) ; Emphasize the truth value FALSE
581 In contexts where a truth value is expected, any non-`nil' value is
582 considered to be TRUE. However, `t' is the preferred way to represent
583 the truth value TRUE. When you need to choose a value which represents
584 TRUE, and there is no other basis for choosing, use `t'. The symbol
585 `t' always has value `t'.
587 In XEmacs Lisp, `nil' and `t' are special symbols that always
588 evaluate to themselves. This is so that you do not need to quote them
589 to use them as constants in a program. An attempt to change their
590 values results in a `setting-constant' error. *Note Accessing
594 File: lispref.info, Node: Evaluation Notation, Next: Printing Notation, Prev: nil and t, Up: Conventions
599 A Lisp expression that you can evaluate is called a "form".
600 Evaluating a form always produces a result, which is a Lisp object. In
601 the examples in this manual, this is indicated with `=>':
606 You can read this as "`(car '(1 2))' evaluates to 1".
608 When a form is a macro call, it expands into a new form for Lisp to
609 evaluate. We show the result of the expansion with `==>'. We may or
610 may not show the actual result of the evaluation of the expanded form.
613 ==> (car (cdr '(a b c)))
616 Sometimes to help describe one form we show another form that
617 produces identical results. The exact equivalence of two forms is
620 (cons 'a nil) == (list 'a)
623 File: lispref.info, Node: Printing Notation, Next: Error Messages, Prev: Evaluation Notation, Up: Conventions
628 Many of the examples in this manual print text when they are
629 evaluated. If you execute example code in a Lisp Interaction buffer
630 (such as the buffer `*scratch*'), the printed text is inserted into the
631 buffer. If you execute the example by other means (such as by
632 evaluating the function `eval-region'), the printed text is displayed
633 in the echo area. You should be aware that text displayed in the echo
634 area is truncated to a single line.
636 Examples in this manual indicate printed text with `-|',
637 irrespective of where that text goes. The value returned by evaluating
638 the form (here `bar') follows on a separate line.
640 (progn (print 'foo) (print 'bar))
646 File: lispref.info, Node: Error Messages, Next: Buffer Text Notation, Prev: Printing Notation, Up: Conventions
651 Some examples signal errors. This normally displays an error message
652 in the echo area. We show the error message on a line starting with
653 `error-->'. Note that `error-->' itself does not appear in the echo
657 error--> Wrong type argument: integer-or-marker-p, x
660 File: lispref.info, Node: Buffer Text Notation, Next: Format of Descriptions, Prev: Error Messages, Up: Conventions
665 Some examples show modifications to text in a buffer, with "before"
666 and "after" versions of the text. These examples show the contents of
667 the buffer in question between two lines of dashes containing the buffer
668 name. In addition, `-!-' indicates the location of point. (The symbol
669 for point, of course, is not part of the text in the buffer; it
670 indicates the place _between_ two characters where point is located.)
672 ---------- Buffer: foo ----------
673 This is the -!-contents of foo.
674 ---------- Buffer: foo ----------
678 ---------- Buffer: foo ----------
679 This is the changed -!-contents of foo.
680 ---------- Buffer: foo ----------
683 File: lispref.info, Node: Format of Descriptions, Prev: Buffer Text Notation, Up: Conventions
685 Format of Descriptions
686 ----------------------
688 Functions, variables, macros, commands, user options, and special
689 forms are described in this manual in a uniform format. The first line
690 of a description contains the name of the item followed by its
691 arguments, if any. The category--function, variable, or
692 whatever--appears at the beginning of the line. The description
693 follows on succeeding lines, sometimes with examples.
697 * A Sample Function Description:: A description of an imaginary
699 * A Sample Variable Description:: A description of an imaginary
701 `electric-future-map'.
704 File: lispref.info, Node: A Sample Function Description, Next: A Sample Variable Description, Up: Format of Descriptions
706 A Sample Function Description
707 .............................
709 In a function description, the name of the function being described
710 appears first. It is followed on the same line by a list of parameters.
711 The names used for the parameters are also used in the body of the
714 The appearance of the keyword `&optional' in the parameter list
715 indicates that the arguments for subsequent parameters may be omitted
716 (omitted parameters default to `nil'). Do not write `&optional' when
717 you call the function.
719 The keyword `&rest' (which will always be followed by a single
720 parameter) indicates that any number of arguments can follow. The value
721 of the single following parameter will be a list of all these arguments.
722 Do not write `&rest' when you call the function.
724 Here is a description of an imaginary function `foo':
726 - Function: foo integer1 &optional integer2 &rest integers
727 The function `foo' subtracts INTEGER1 from INTEGER2, then adds all
728 the rest of the arguments to the result. If INTEGER2 is not
729 supplied, then the number 19 is used by default.
742 Any parameter whose name contains the name of a type (e.g., INTEGER,
743 INTEGER1 or BUFFER) is expected to be of that type. A plural of a type
744 (such as BUFFERS) often means a list of objects of that type.
745 Parameters named OBJECT may be of any type. (*Note Lisp Data Types::,
746 for a list of XEmacs object types.) Parameters with other sorts of
747 names (e.g., NEW-FILE) are discussed specifically in the description of
748 the function. In some sections, features common to parameters of
749 several functions are described at the beginning.
751 *Note Lambda Expressions::, for a more complete description of
752 optional and rest arguments.
754 Command, macro, and special form descriptions have the same format,
755 but the word `Function' is replaced by `Command', `Macro', or `Special
756 Form', respectively. Commands are simply functions that may be called
757 interactively; macros process their arguments differently from functions
758 (the arguments are not evaluated), but are presented the same way.
760 Special form descriptions use a more complex notation to specify
761 optional and repeated parameters because they can break the argument
762 list down into separate arguments in more complicated ways.
763 ``[OPTIONAL-ARG]'' means that OPTIONAL-ARG is optional and
764 `REPEATED-ARGS...' stands for zero or more arguments. Parentheses are
765 used when several arguments are grouped into additional levels of list
766 structure. Here is an example:
768 - Special Form: count-loop (VAR [FROM TO [INC]]) BODY...
769 This imaginary special form implements a loop that executes the
770 BODY forms and then increments the variable VAR on each iteration.
771 On the first iteration, the variable has the value FROM; on
772 subsequent iterations, it is incremented by 1 (or by INC if that
773 is given). The loop exits before executing BODY if VAR equals TO.
777 (prin1 i) (princ " ")
778 (prin1 (aref vector i)) (terpri))
780 If FROM and TO are omitted, then VAR is bound to `nil' before the
781 loop begins, and the loop exits if VAR is non-`nil' at the
782 beginning of an iteration. Here is an example:
789 In this special form, the arguments FROM and TO are optional, but
790 must both be present or both absent. If they are present, INC may
791 optionally be specified as well. These arguments are grouped with
792 the argument VAR into a list, to distinguish them from BODY, which
793 includes all remaining elements of the form.
796 File: lispref.info, Node: A Sample Variable Description, Prev: A Sample Function Description, Up: Format of Descriptions
798 A Sample Variable Description
799 .............................
801 A "variable" is a name that can hold a value. Although any variable
802 can be set by the user, certain variables that exist specifically so
803 that users can change them are called "user options". Ordinary
804 variables and user options are described using a format like that for
805 functions except that there are no arguments.
807 Here is a description of the imaginary `electric-future-map'
810 - Variable: electric-future-map
811 The value of this variable is a full keymap used by Electric
812 Command Future mode. The functions in this map allow you to edit
813 commands you have not yet thought about executing.
815 User option descriptions have the same format, but `Variable' is
816 replaced by `User Option'.
819 File: lispref.info, Node: Acknowledgements, Prev: Conventions, Up: Introduction
824 This manual was based on the GNU Emacs Lisp Reference Manual, version
825 2.4, written by Robert Krawitz, Bil Lewis, Dan LaLiberte, Richard M.
826 Stallman and Chris Welty, the volunteers of the GNU manual group, in an
827 effort extending over several years. Robert J. Chassell helped to
828 review and edit the manual, with the support of the Defense Advanced
829 Research Projects Agency, ARPA Order 6082, arranged by Warren A. Hunt,
830 Jr. of Computational Logic, Inc.
832 Ben Wing adapted this manual for XEmacs 19.14 and 20.0, and earlier
833 for Lucid Emacs 19.10, XEmacs 19.12, and XEmacs 19.13. He is the sole
834 author of many of the manual sections, in particular the XEmacs-specific
835 sections: events, faces, extents, glyphs, specifiers, toolbar, menubars,
836 scrollbars, dialog boxes, devices, consoles, hash tables, range tables,
837 char tables, databases, and others. The section on annotations was
838 originally written by Chuck Thompson. Corrections to v3.1 and later
839 were done by Martin Buchholz, Steve Baur, and Hrvoje Niksic.
841 Corrections to the original GNU Emacs Lisp Reference Manual were
842 supplied by Karl Berry, Jim Blandy, Bard Bloom, Stephane Boucher, David
843 Boyes, Alan Carroll, Richard Davis, Lawrence R. Dodd, Peter Doornbosch,
844 David A. Duff, Chris Eich, Beverly Erlebacher, David Eckelkamp, Ralf
845 Fassel, Eirik Fuller, Stephen Gildea, Bob Glickstein, Eric Hanchrow,
846 George Hartzell, Nathan Hess, Masayuki Ida, Dan Jacobson, Jak Kirman,
847 Bob Knighten, Frederick M. Korz, Joe Lammens, Glenn M. Lewis, K. Richard
848 Magill, Brian Marick, Roland McGrath, Skip Montanaro, John Gardiner
849 Myers, Thomas A. Peterson, Francesco Potorti, Friedrich Pukelsheim,
850 Arnold D. Robbins, Raul Rockwell, Per Starback, Shinichirou Sugou, Kimmo
851 Suominen, Edward Tharp, Bill Trost, Rickard Westman, Jean White, Matthew
852 Wilding, Carl Witty, Dale Worley, Rusty Wright, and David D. Zuhn.
855 File: lispref.info, Node: Lisp Data Types, Next: Numbers, Prev: Introduction, Up: Top
860 A Lisp "object" is a piece of data used and manipulated by Lisp
861 programs. For our purposes, a "type" or "data type" is a set of
864 Every object belongs to at least one type. Objects of the same type
865 have similar structures and may usually be used in the same contexts.
866 Types can overlap, and objects can belong to two or more types.
867 Consequently, we can ask whether an object belongs to a particular type,
868 but not for "the" type of an object.
870 A few fundamental object types are built into XEmacs. These, from
871 which all other types are constructed, are called "primitive types".
872 Each object belongs to one and only one primitive type. These types
873 include "integer", "character" (starting with XEmacs 20.0), "float",
874 "cons", "symbol", "string", "vector", "bit-vector", "subr",
875 "compiled-function", "hash-table", "range-table", "char-table",
876 "weak-list", and several special types, such as "buffer", that are
877 related to editing. (*Note Editing Types::.)
879 Each primitive type has a corresponding Lisp function that checks
880 whether an object is a member of that type.
882 Note that Lisp is unlike many other languages in that Lisp objects
883 are "self-typing": the primitive type of the object is implicit in the
884 object itself. For example, if an object is a vector, nothing can treat
885 it as a number; Lisp knows it is a vector, not a number.
887 In most languages, the programmer must declare the data type of each
888 variable, and the type is known by the compiler but not represented in
889 the data. Such type declarations do not exist in XEmacs Lisp. A Lisp
890 variable can have any type of value, and it remembers whatever value
891 you store in it, type and all.
893 This chapter describes the purpose, printed representation, and read
894 syntax of each of the standard types in Emacs Lisp. Details on how to
895 use these types can be found in later chapters.
899 * Printed Representation:: How Lisp objects are represented as text.
900 * Comments:: Comments and their formatting conventions.
901 * Primitive Types:: List of all primitive types in XEmacs.
902 * Programming Types:: Types found in all Lisp systems.
903 * Editing Types:: Types specific to XEmacs.
904 * Window-System Types:: Types specific to windowing systems.
905 * Type Predicates:: Tests related to types.
906 * Equality Predicates:: Tests of equality between any two objects.
909 File: lispref.info, Node: Printed Representation, Next: Comments, Up: Lisp Data Types
911 Printed Representation and Read Syntax
912 ======================================
914 The "printed representation" of an object is the format of the
915 output generated by the Lisp printer (the function `prin1') for that
916 object. The "read syntax" of an object is the format of the input
917 accepted by the Lisp reader (the function `read') for that object.
918 Most objects have more than one possible read syntax. Some types of
919 object have no read syntax; except for these cases, the printed
920 representation of an object is also a read syntax for it.
922 In other languages, an expression is text; it has no other form. In
923 Lisp, an expression is primarily a Lisp object and only secondarily the
924 text that is the object's read syntax. Often there is no need to
925 emphasize this distinction, but you must keep it in the back of your
926 mind, or you will occasionally be very confused.
928 Every type has a printed representation. Some types have no read
929 syntax, since it may not make sense to enter objects of these types
930 directly in a Lisp program. For example, the buffer type does not have
931 a read syntax. Objects of these types are printed in "hash notation":
932 the characters `#<' followed by a descriptive string (typically the
933 type name followed by the name of the object), and closed with a
934 matching `>'. Hash notation cannot be read at all, so the Lisp reader
935 signals the error `invalid-read-syntax' whenever it encounters `#<'.
938 => #<buffer "objects.texi">
940 When you evaluate an expression interactively, the Lisp interpreter
941 first reads the textual representation of it, producing a Lisp object,
942 and then evaluates that object (*note Evaluation::). However,
943 evaluation and reading are separate activities. Reading returns the
944 Lisp object represented by the text that is read; the object may or may
945 not be evaluated later. *Note Input Functions::, for a description of
946 `read', the basic function for reading objects.
949 File: lispref.info, Node: Comments, Next: Primitive Types, Prev: Printed Representation, Up: Lisp Data Types
954 A "comment" is text that is written in a program only for the sake
955 of humans that read the program, and that has no effect on the meaning
956 of the program. In Lisp, a semicolon (`;') starts a comment if it is
957 not within a string or character constant. The comment continues to
958 the end of line. The Lisp reader discards comments; they do not become
959 part of the Lisp objects which represent the program within the Lisp
962 The `#@COUNT' construct, which skips the next COUNT characters, is
963 useful for program-generated comments containing binary data. The
964 XEmacs Lisp byte compiler uses this in its output files (*note Byte
965 Compilation::). It isn't meant for source files, however.
967 *Note Comment Tips::, for conventions for formatting comments.
970 File: lispref.info, Node: Primitive Types, Next: Programming Types, Prev: Comments, Up: Lisp Data Types
975 For reference, here is a list of all the primitive types that may
976 exist in XEmacs. Note that some of these types may not exist in some
977 XEmacs executables; that depends on the options that XEmacs was
1054 * window-configuration
1058 In addition, the following special types are created internally but
1059 will never be seen by Lisp code. You may encounter them, however, if
1060 you are debugging XEmacs. The printed representation of these objects
1061 begins `#<INTERNAL EMACS BUG', which indicates to the Lisp programmer
1062 that he has found an internal bug in XEmacs if he ever encounters any
1083 * symbol-value-buffer-local
1085 * symbol-value-forward
1087 * symbol-value-lisp-magic
1089 * symbol-value-varalias
1094 File: lispref.info, Node: Programming Types, Next: Editing Types, Prev: Primitive Types, Up: Lisp Data Types
1099 There are two general categories of types in XEmacs Lisp: those
1100 having to do with Lisp programming, and those having to do with
1101 editing. The former exist in many Lisp implementations, in one form or
1102 another. The latter are unique to XEmacs Lisp.
1106 * Integer Type:: Numbers without fractional parts.
1107 * Floating Point Type:: Numbers with fractional parts and with a large range.
1108 * Character Type:: The representation of letters, numbers and
1110 * Symbol Type:: A multi-use object that refers to a function,
1111 variable, or property list, and has a unique identity.
1112 * Sequence Type:: Both lists and arrays are classified as sequences.
1113 * Cons Cell Type:: Cons cells, and lists (which are made from cons cells).
1114 * Array Type:: Arrays include strings and vectors.
1115 * String Type:: An (efficient) array of characters.
1116 * Vector Type:: One-dimensional arrays.
1117 * Bit Vector Type:: An (efficient) array of bits.
1118 * Function Type:: A piece of executable code you can call from elsewhere.
1119 * Macro Type:: A method of expanding an expression into another
1120 expression, more fundamental but less pretty.
1121 * Primitive Function Type:: A function written in C, callable from Lisp.
1122 * Compiled-Function Type:: A function written in Lisp, then compiled.
1123 * Autoload Type:: A type used for automatically loading seldom-used
1125 * Char Table Type:: A mapping from characters to Lisp objects.
1126 * Hash Table Type:: A fast mapping between Lisp objects.
1127 * Range Table Type:: A mapping from ranges of integers to Lisp objects.
1128 * Weak List Type:: A list with special garbage-collection properties.
1131 File: lispref.info, Node: Integer Type, Next: Floating Point Type, Up: Programming Types
1136 The range of values for integers in XEmacs Lisp is -134217728 to
1137 134217727 (28 bits; i.e., -2**27 to 2**27 - 1) on most machines. (Some
1138 machines, in particular 64-bit machines such as the DEC Alpha, may
1139 provide a wider range.) It is important to note that the XEmacs Lisp
1140 arithmetic functions do not check for overflow. Thus `(1+ 134217727)'
1141 is -134217728 on most machines. (However, you _will_ get an error if
1142 you attempt to read an out-of-range number using the Lisp reader.)
1144 The read syntax for integers is a sequence of (base ten) digits with
1145 an optional sign at the beginning. (The printed representation produced
1146 by the Lisp interpreter never has a leading `+'.)
1148 -1 ; The integer -1.
1150 +1 ; Also the integer 1.
1151 268435457 ; Causes an error on a 28-bit implementation.
1153 *Note Numbers::, for more information.
1156 File: lispref.info, Node: Floating Point Type, Next: Character Type, Prev: Integer Type, Up: Programming Types
1161 XEmacs supports floating point numbers. The precise range of
1162 floating point numbers is machine-specific.
1164 The printed representation for floating point numbers requires either
1165 a decimal point (with at least one digit following), an exponent, or
1166 both. For example, `1500.0', `15e2', `15.0e2', `1.5e3', and `.15e4'
1167 are five ways of writing a floating point number whose value is 1500.
1168 They are all equivalent.
1170 *Note Numbers::, for more information.