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authorRichard M. Stallman <rms@gnu.org>1994-03-21 17:36:52 +0000
committerRichard M. Stallman <rms@gnu.org>1994-03-21 17:36:52 +0000
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+@c -*-texinfo-*-
+@c This is part of the GNU Emacs Lisp Reference Manual.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
+@c See the file elisp.texi for copying conditions.
+@setfilename ../info/intro
+
+@node Copying, Introduction, Top, Top
+@comment node-name, next, previous, up
+@unnumbered GNU GENERAL PUBLIC LICENSE
+@center Version 2, June 1991
+
+@display
+Copyright @copyright{} 1989, 1991 Free Software Foundation, Inc.
+675 Mass Ave, Cambridge, MA 02139, USA
+
+Everyone is permitted to copy and distribute verbatim copies
+of this license document, but changing it is not allowed.
+@end display
+
+@unnumberedsec Preamble
+
+ The licenses for most software are designed to take away your
+freedom to share and change it. By contrast, the GNU General Public
+License is intended to guarantee your freedom to share and change free
+software---to make sure the software is free for all its users. This
+General Public License applies to most of the Free Software
+Foundation's software and to any other program whose authors commit to
+using it. (Some other Free Software Foundation software is covered by
+the GNU Library General Public License instead.) You can apply it to
+your programs, too.
+
+ When we speak of free software, we are referring to freedom, not
+price. Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+this service if you wish), that you receive source code or can get it
+if you want it, that you can change the software or use pieces of it
+in new free programs; and that you know you can do these things.
+
+ To protect your rights, we need to make restrictions that forbid
+anyone to deny you these rights or to ask you to surrender the rights.
+These restrictions translate to certain responsibilities for you if you
+distribute copies of the software, or if you modify it.
+
+ For example, if you distribute copies of such a program, whether
+gratis or for a fee, you must give the recipients all the rights that
+you have. You must make sure that they, too, receive or can get the
+source code. And you must show them these terms so they know their
+rights.
+
+ We protect your rights with two steps: (1) copyright the software, and
+(2) offer you this license which gives you legal permission to copy,
+distribute and/or modify the software.
+
+ Also, for each author's protection and ours, we want to make certain
+that everyone understands that there is no warranty for this free
+software. If the software is modified by someone else and passed on, we
+want its recipients to know that what they have is not the original, so
+that any problems introduced by others will not reflect on the original
+authors' reputations.
+
+ Finally, any free program is threatened constantly by software
+patents. We wish to avoid the danger that redistributors of a free
+program will individually obtain patent licenses, in effect making the
+program proprietary. To prevent this, we have made it clear that any
+patent must be licensed for everyone's free use or not licensed at all.
+
+ The precise terms and conditions for copying, distribution and
+modification follow.
+
+@iftex
+@unnumberedsec TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+@end iftex
+@ifinfo
+@center TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+@end ifinfo
+
+@enumerate 0
+@item
+This License applies to any program or other work which contains
+a notice placed by the copyright holder saying it may be distributed
+under the terms of this General Public License. The ``Program'', below,
+refers to any such program or work, and a ``work based on the Program''
+means either the Program or any derivative work under copyright law:
+that is to say, a work containing the Program or a portion of it,
+either verbatim or with modifications and/or translated into another
+language. (Hereinafter, translation is included without limitation in
+the term ``modification''.) Each licensee is addressed as ``you''.
+
+Activities other than copying, distribution and modification are not
+covered by this License; they are outside its scope. The act of
+running the Program is not restricted, and the output from the Program
+is covered only if its contents constitute a work based on the
+Program (independent of having been made by running the Program).
+Whether that is true depends on what the Program does.
+
+@item
+You may copy and distribute verbatim copies of the Program's
+source code as you receive it, in any medium, provided that you
+conspicuously and appropriately publish on each copy an appropriate
+copyright notice and disclaimer of warranty; keep intact all the
+notices that refer to this License and to the absence of any warranty;
+and give any other recipients of the Program a copy of this License
+along with the Program.
+
+You may charge a fee for the physical act of transferring a copy, and
+you may at your option offer warranty protection in exchange for a fee.
+
+@item
+You may modify your copy or copies of the Program or any portion
+of it, thus forming a work based on the Program, and copy and
+distribute such modifications or work under the terms of Section 1
+above, provided that you also meet all of these conditions:
+
+@enumerate a
+@item
+You must cause the modified files to carry prominent notices
+stating that you changed the files and the date of any change.
+
+@item
+You must cause any work that you distribute or publish, that in
+whole or in part contains or is derived from the Program or any
+part thereof, to be licensed as a whole at no charge to all third
+parties under the terms of this License.
+
+@item
+If the modified program normally reads commands interactively
+when run, you must cause it, when started running for such
+interactive use in the most ordinary way, to print or display an
+announcement including an appropriate copyright notice and a
+notice that there is no warranty (or else, saying that you provide
+a warranty) and that users may redistribute the program under
+these conditions, and telling the user how to view a copy of this
+License. (Exception: if the Program itself is interactive but
+does not normally print such an announcement, your work based on
+the Program is not required to print an announcement.)
+@end enumerate
+
+These requirements apply to the modified work as a whole. If
+identifiable sections of that work are not derived from the Program,
+and can be reasonably considered independent and separate works in
+themselves, then this License, and its terms, do not apply to those
+sections when you distribute them as separate works. But when you
+distribute the same sections as part of a whole which is a work based
+on the Program, the distribution of the whole must be on the terms of
+this License, whose permissions for other licensees extend to the
+entire whole, and thus to each and every part regardless of who wrote it.
+
+Thus, it is not the intent of this section to claim rights or contest
+your rights to work written entirely by you; rather, the intent is to
+exercise the right to control the distribution of derivative or
+collective works based on the Program.
+
+In addition, mere aggregation of another work not based on the Program
+with the Program (or with a work based on the Program) on a volume of
+a storage or distribution medium does not bring the other work under
+the scope of this License.
+
+@item
+You may copy and distribute the Program (or a work based on it,
+under Section 2) in object code or executable form under the terms of
+Sections 1 and 2 above provided that you also do one of the following:
+
+@enumerate a
+@item
+Accompany it with the complete corresponding machine-readable
+source code, which must be distributed under the terms of Sections
+1 and 2 above on a medium customarily used for software interchange; or,
+
+@item
+Accompany it with a written offer, valid for at least three
+years, to give any third party, for a charge no more than your
+cost of physically performing source distribution, a complete
+machine-readable copy of the corresponding source code, to be
+distributed under the terms of Sections 1 and 2 above on a medium
+customarily used for software interchange; or,
+
+@item
+Accompany it with the information you received as to the offer
+to distribute corresponding source code. (This alternative is
+allowed only for noncommercial distribution and only if you
+received the program in object code or executable form with such
+an offer, in accord with Subsection b above.)
+@end enumerate
+
+The source code for a work means the preferred form of the work for
+making modifications to it. For an executable work, complete source
+code means all the source code for all modules it contains, plus any
+associated interface definition files, plus the scripts used to
+control compilation and installation of the executable. However, as a
+special exception, the source code distributed need not include
+anything that is normally distributed (in either source or binary
+form) with the major components (compiler, kernel, and so on) of the
+operating system on which the executable runs, unless that component
+itself accompanies the executable.
+
+If distribution of executable or object code is made by offering
+access to copy from a designated place, then offering equivalent
+access to copy the source code from the same place counts as
+distribution of the source code, even though third parties are not
+compelled to copy the source along with the object code.
+
+@item
+You may not copy, modify, sublicense, or distribute the Program
+except as expressly provided under this License. Any attempt
+otherwise to copy, modify, sublicense or distribute the Program is
+void, and will automatically terminate your rights under this License.
+However, parties who have received copies, or rights, from you under
+this License will not have their licenses terminated so long as such
+parties remain in full compliance.
+
+@item
+You are not required to accept this License, since you have not
+signed it. However, nothing else grants you permission to modify or
+distribute the Program or its derivative works. These actions are
+prohibited by law if you do not accept this License. Therefore, by
+modifying or distributing the Program (or any work based on the
+Program), you indicate your acceptance of this License to do so, and
+all its terms and conditions for copying, distributing or modifying
+the Program or works based on it.
+
+@item
+Each time you redistribute the Program (or any work based on the
+Program), the recipient automatically receives a license from the
+original licensor to copy, distribute or modify the Program subject to
+these terms and conditions. You may not impose any further
+restrictions on the recipients' exercise of the rights granted herein.
+You are not responsible for enforcing compliance by third parties to
+this License.
+
+@item
+If, as a consequence of a court judgment or allegation of patent
+infringement or for any other reason (not limited to patent issues),
+conditions are imposed on you (whether by court order, agreement or
+otherwise) that contradict the conditions of this License, they do not
+excuse you from the conditions of this License. If you cannot
+distribute so as to satisfy simultaneously your obligations under this
+License and any other pertinent obligations, then as a consequence you
+may not distribute the Program at all. For example, if a patent
+license would not permit royalty-free redistribution of the Program by
+all those who receive copies directly or indirectly through you, then
+the only way you could satisfy both it and this License would be to
+refrain entirely from distribution of the Program.
+
+If any portion of this section is held invalid or unenforceable under
+any particular circumstance, the balance of the section is intended to
+apply and the section as a whole is intended to apply in other
+circumstances.
+
+It is not the purpose of this section to induce you to infringe any
+patents or other property right claims or to contest validity of any
+such claims; this section has the sole purpose of protecting the
+integrity of the free software distribution system, which is
+implemented by public license practices. Many people have made
+generous contributions to the wide range of software distributed
+through that system in reliance on consistent application of that
+system; it is up to the author/donor to decide if he or she is willing
+to distribute software through any other system and a licensee cannot
+impose that choice.
+
+This section is intended to make thoroughly clear what is believed to
+be a consequence of the rest of this License.
+
+@item
+If the distribution and/or use of the Program is restricted in
+certain countries either by patents or by copyrighted interfaces, the
+original copyright holder who places the Program under this License
+may add an explicit geographical distribution limitation excluding
+those countries, so that distribution is permitted only in or among
+countries not thus excluded. In such case, this License incorporates
+the limitation as if written in the body of this License.
+
+@item
+The Free Software Foundation may publish revised and/or new versions
+of the General Public License from time to time. Such new versions will
+be similar in spirit to the present version, but may differ in detail to
+address new problems or concerns.
+
+Each version is given a distinguishing version number. If the Program
+specifies a version number of this License which applies to it and ``any
+later version'', you have the option of following the terms and conditions
+either of that version or of any later version published by the Free
+Software Foundation. If the Program does not specify a version number of
+this License, you may choose any version ever published by the Free Software
+Foundation.
+
+@item
+If you wish to incorporate parts of the Program into other free
+programs whose distribution conditions are different, write to the author
+to ask for permission. For software which is copyrighted by the Free
+Software Foundation, write to the Free Software Foundation; we sometimes
+make exceptions for this. Our decision will be guided by the two goals
+of preserving the free status of all derivatives of our free software and
+of promoting the sharing and reuse of software generally.
+
+@iftex
+@heading NO WARRANTY
+@end iftex
+@ifinfo
+@center NO WARRANTY
+@end ifinfo
+
+@item
+BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
+FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW@. EXCEPT WHEN
+OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
+PROVIDE THE PROGRAM ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
+OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE@. THE ENTIRE RISK AS
+TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU@. SHOULD THE
+PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
+REPAIR OR CORRECTION.
+
+@item
+IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
+REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
+INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
+OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
+TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
+YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
+PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGES.
+@end enumerate
+
+@iftex
+@heading END OF TERMS AND CONDITIONS
+@end iftex
+@ifinfo
+@center END OF TERMS AND CONDITIONS
+@end ifinfo
+
+@page
+@unnumberedsec How to Apply These Terms to Your New Programs
+
+ If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+ To do so, attach the following notices to the program. It is safest
+to attach them to the start of each source file to most effectively
+convey the exclusion of warranty; and each file should have at least
+the ``copyright'' line and a pointer to where the full notice is found.
+
+@smallexample
+@var{one line to give the program's name and an idea of what it does.}
+Copyright (C) 19@var{yy} @var{name of author}
+
+This program is free software; you can redistribute it and/or
+modify it under the terms of the GNU General Public License
+as published by the Free Software Foundation; either version 2
+of the License, or (at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE@. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+@end smallexample
+
+Also add information on how to contact you by electronic and paper mail.
+
+If the program is interactive, make it output a short notice like this
+when it starts in an interactive mode:
+
+@smallexample
+Gnomovision version 69, Copyright (C) 19@var{yy} @var{name of author}
+Gnomovision comes with ABSOLUTELY NO WARRANTY; for details
+type `show w'. This is free software, and you are welcome
+to redistribute it under certain conditions; type `show c'
+for details.
+@end smallexample
+
+The hypothetical commands @samp{show w} and @samp{show c} should show
+the appropriate parts of the General Public License. Of course, the
+commands you use may be called something other than @samp{show w} and
+@samp{show c}; they could even be mouse-clicks or menu items---whatever
+suits your program.
+
+You should also get your employer (if you work as a programmer) or your
+school, if any, to sign a ``copyright disclaimer'' for the program, if
+necessary. Here is a sample; alter the names:
+
+@smallexample
+@group
+Yoyodyne, Inc., hereby disclaims all copyright
+interest in the program `Gnomovision'
+(which makes passes at compilers) written
+by James Hacker.
+
+@var{signature of Ty Coon}, 1 April 1989
+Ty Coon, President of Vice
+@end group
+@end smallexample
+
+This General Public License does not permit incorporating your program into
+proprietary programs. If your program is a subroutine library, you may
+consider it more useful to permit linking proprietary applications with the
+library. If this is what you want to do, use the GNU Library General
+Public License instead of this License.
+
+@node Introduction, Types of Lisp Object, Copying, Top
+@chapter Introduction
+
+ Most of the GNU Emacs text editor is written in the programming
+language called Emacs Lisp. You can write new code in Emacs Lisp and
+install it as an extension to the editor. However, Emacs Lisp is more
+than a mere ``extension language''; it is a full computer programming
+language in its own right. You can use it as you would any other
+programming language.
+
+ Because Emacs Lisp is designed for use in an editor, it has special
+features for scanning and parsing text as well as features for handling
+files, buffers, displays, subprocesses, and so on. Emacs Lisp is
+closely integrated with the editing facilities; thus, editing commands
+are functions that can also conveniently be called from Lisp programs,
+and parameters for customization are ordinary Lisp variables.
+
+ This manual describes Emacs Lisp, presuming considerable familiarity
+with the use of Emacs for editing. (See @cite{The GNU Emacs Manual},
+for this basic information.) Generally speaking, the earlier chapters
+describe features of Emacs Lisp that have counterparts in many
+programming languages, and later chapters describe features that are
+peculiar to Emacs Lisp or relate specifically to editing.
+
+ This is edition 2.3.
+
+@menu
+* Caveats:: Flaws and a request for help.
+* Lisp History:: Emacs Lisp is descended from Maclisp.
+* Conventions:: How the manual is formatted.
+* Acknowledgements:: The authors, editors, and sponsors of this manual.
+@end menu
+
+@node Caveats
+@section Caveats
+
+ This manual has gone through numerous drafts. It is nearly complete
+but not flawless. There are a few sections which are not included,
+either because we consider them secondary (such as most of the
+individual modes) or because they are yet to be written.
+
+ Because we are not able to deal with them completely, we have left out
+several parts intentionally. This includes most information about usage
+on VMS.
+
+ The manual should be fully correct in what it does cover, and it is
+therefore open to criticism on anything it says---from specific examples
+and descriptive text, to the ordering of chapters and sections. If
+something is confusing, or you find that you have to look at the sources
+or experiment to learn something not covered in the manual, then perhaps
+the manual should be fixed. Please let us know.
+
+@iftex
+ As you use the manual, we ask that you mark pages with corrections so
+you can later look them up and send them in. If you think of a simple,
+real life example for a function or group of functions, please make an
+effort to write it up and send it in. Please reference any comments to
+the chapter name, section name, and function name, as appropriate, since
+page numbers and chapter and section numbers will change. Also state
+the number of the edition which you are criticizing.
+@end iftex
+@ifinfo
+
+As you use this manual, we ask that you send corrections as soon as you
+find them. If you think of a simple, real life example for a function
+or group of functions, please make an effort to write it up and send it
+in. Please reference any comments to the node name and function or
+variable name, as appropriate. Also state the number of the edition
+which you are criticizing.
+@end ifinfo
+
+Please mail comments and corrections to
+
+@example
+bug-lisp-manual@@prep.ai.mit.edu
+@end example
+
+@noindent
+We let mail to this list accumulate unread until someone decides to
+apply the corrections. Months, and sometimes years, go by between
+updates. So please attach no significance to the lack of a reply---your
+mail @emph{will} be acted on in due time. If you want to contact the
+Emacs maintainers more quickly, send mail to
+@code{bug-gnu-emacs@@prep.ai.mit.edu}.
+
+@display
+ --Bil Lewis, Dan LaLiberte, Richard Stallman
+@end display
+
+@node Lisp History
+@section Lisp History
+@cindex Lisp history
+
+ Lisp (LISt Processing language) was first developed in the late 1950s
+at the Massachusetts Institute of Technology for research in artificial
+intelligence. The great power of the Lisp language makes it superior
+for other purposes as well, such as writing editing commands.
+
+@cindex Maclisp
+@cindex Common Lisp
+ Dozens of Lisp implementations have been built over the years, each
+with its own idiosyncrasies. Many of them were inspired by Maclisp,
+which was written in the 1960's at MIT's Project MAC. Eventually the
+implementors of the descendents of Maclisp came together and developed a
+standard for Lisp systems, called Common Lisp.
+
+ GNU Emacs Lisp is largely inspired by Maclisp, and a little by Common
+Lisp. If you know Common Lisp, you will notice many similarities.
+However, many of the features of Common Lisp have been omitted or
+simplified in order to reduce the memory requirements of GNU Emacs.
+Sometimes the simplifications are so drastic that a Common Lisp user
+might be very confused. We will occasionally point out how GNU Emacs
+Lisp differs from Common Lisp. If you don't know Common Lisp, don't
+worry about it; this manual is self-contained.
+
+@node Conventions
+@section Conventions
+
+This section explains the notational conventions that are used in this
+manual. You may want to skip this section and refer back to it later.
+
+@menu
+* Some Terms:: Explanation of terms we use in this manual.
+* nil and t:: How the symbols @code{nil} and @code{t} are used.
+* Evaluation Notation:: The format we use for examples of evaluation.
+* Printing Notation:: The format we use for examples that print output.
+* Error Messages:: The format we use for examples of errors.
+* Buffer Text Notation:: The format we use for buffer contents in examples.
+* Format of Descriptions:: Notation for describing functions, variables, etc.
+@end menu
+
+@node Some Terms
+@subsection Some Terms
+
+ Throughout this manual, the phrases ``the Lisp reader'' and ``the Lisp
+printer'' are used to refer to those routines in Lisp that convert
+textual representations of Lisp objects into actual objects, and vice
+versa. @xref{Printed Representation}, for more details. You, the
+person reading this manual, are thought of as ``the programmer'' and are
+addressed as ``you''. ``The user'' is the person who uses Lisp programs
+including those you write.
+
+@cindex fonts
+ Examples of Lisp code appear in this font or form: @code{(list 1 2
+3)}. Names that represent arguments or metasyntactic variables appear
+in this font or form: @var{first-number}.
+
+@node nil and t
+@subsection @code{nil} and @code{t}
+@cindex @code{nil}, uses of
+@cindex truth value
+@cindex boolean
+@cindex false
+
+ In Lisp, the symbol @code{nil} is overloaded with three meanings: it
+is a symbol with the name @samp{nil}; it is the logical truth value
+@var{false}; and it is the empty list---the list of zero elements.
+When used as a variable, @code{nil} always has the value @code{nil}.
+
+ As far as the Lisp reader is concerned, @samp{()} and @samp{nil} are
+identical: they stand for the same object, the symbol @code{nil}. The
+different ways of writing the symbol are intended entirely for human
+readers. After the Lisp reader has read either @samp{()} or @samp{nil},
+there is no way to determine which representation was actually written
+by the programmer.
+
+ In this manual, we use @code{()} when we wish to emphasize that it
+means the empty list, and we use @code{nil} when we wish to emphasize
+that it means the truth value @var{false}. That is a good convention to use
+in Lisp programs also.
+
+@example
+(cons 'foo ()) ; @r{Emphasize the empty list}
+(not nil) ; @r{Emphasize the truth value @var{false}}
+@end example
+
+@cindex @code{t} and truth
+@cindex true
+ In contexts where a truth value is expected, any non-@code{nil} value
+is considered to be @var{true}. However, @code{t} is the preferred way
+to represent the truth value @var{true}. When you need to choose a
+value which represents @var{true}, and there is no other basis for
+choosing, use @code{t}. The symbol @code{t} always has value @code{t}.
+
+ In Emacs Lisp, @code{nil} and @code{t} are special symbols that always
+evaluate to themselves. This is so that you do not need to quote them
+to use them as constants in a program. An attempt to change their
+values results in a @code{setting-constant} error. @xref{Accessing
+Variables}.
+
+@node Evaluation Notation
+@subsection Evaluation Notation
+@cindex evaluation notation
+@cindex documentation notation
+
+ A Lisp expression that you can evaluate is called a @dfn{form}.
+Evaluating a form always produces a result, which is a Lisp object. In
+the examples in this manual, this is indicated with @samp{@result{}}:
+
+@example
+(car '(1 2))
+ @result{} 1
+@end example
+
+@noindent
+You can read this as ``@code{(car '(1 2))} evaluates to 1''.
+
+ When a form is a macro call, it expands into a new form for Lisp to
+evaluate. We show the result of the expansion with
+@samp{@expansion{}}. We may or may not show the actual result of the
+evaluation of the expanded form.
+
+@example
+(third '(a b c))
+ @expansion{} (car (cdr (cdr '(a b c))))
+ @result{} c
+@end example
+
+ Sometimes to help describe one form we show another form which
+produces identical results. The exact equivalence of two forms is
+indicated with @samp{@equiv{}}.
+
+@example
+(make-sparse-keymap) @equiv{} (list 'keymap)
+@end example
+
+@node Printing Notation
+@subsection Printing Notation
+@cindex printing notation
+
+ Many of the examples in this manual print text when they are
+evaluated. If you execute the code from an example in a Lisp
+Interaction buffer (such as the buffer @samp{*scratch*}), the printed
+text is inserted into the buffer. If you execute the example by other
+means (such as by evaluating the function @code{eval-region}), it prints
+text by displaying it in the echo area. You should be aware that text
+displayed in the echo area is truncated to a single line.
+
+ Examples in this manual indicate printed text with @samp{@print{}},
+irrespective of where that text goes. The value returned by evaluating
+the form (here @code{bar}) follows on a separate line.
+
+@example
+@group
+(progn (print 'foo) (print 'bar))
+ @print{} foo
+ @print{} bar
+ @result{} bar
+@end group
+@end example
+
+@node Error Messages
+@subsection Error Messages
+@cindex error message notation
+
+ Some examples signal errors. This normally displays an error message
+in the echo area. We show the error message on a line starting with
+@samp{@error{}}. Note that @samp{@error{}} itself does not appear in
+the echo area.
+
+@example
+(+ 23 'x)
+@error{} Wrong type argument: integer-or-marker-p, x
+@end example
+
+@node Buffer Text Notation
+@subsection Buffer Text Notation
+@cindex buffer text notation
+
+ Some examples show modifications to text in a buffer, with ``before''
+and ``after'' versions of the text. These examples show the contents of
+the buffer in question between two lines of dashes containing the buffer
+name. In addition, @samp{@point{}} indicates the location of point.
+(The symbol for point, of course, is not part of the text in the buffer;
+it indicates the place @emph{between} two characters where point is
+located.)
+
+@example
+---------- Buffer: foo ----------
+This is the @point{}contents of foo.
+---------- Buffer: foo ----------
+
+(insert "changed ")
+ @result{} nil
+---------- Buffer: foo ----------
+This is the changed @point{}contents of foo.
+---------- Buffer: foo ----------
+@end example
+
+@node Format of Descriptions
+@subsection Format of Descriptions
+@cindex description format
+
+ Functions, variables, macros, commands, user options, and special
+forms are described in this manual in a uniform format. The first
+line of a description contains the name of the item followed by its
+arguments, if any.
+@ifinfo
+The category---function, variable, or whatever---appears at the
+beginning of the line.
+@end ifinfo
+@iftex
+The category---function, variable, or whatever---is printed next to the
+right margin.
+@end iftex
+The description follows on succeeding lines, sometimes with examples.
+
+@menu
+* A Sample Function Description:: A description of an imaginary
+ function, @code{foo}.
+* A Sample Variable Description:: A description of an imaginary
+ variable,
+ @code{electric-future-map}.
+@end menu
+
+@node A Sample Function Description
+@subsubsection A Sample Function Description
+@cindex function descriptions
+@cindex command descriptions
+@cindex macro descriptions
+@cindex special form descriptions
+
+ In a function description, the name of the function being described
+appears first. It is followed on the same line by a list of parameters.
+The names used for the parameters are also used in the body of the
+description.
+
+ The appearance of the keyword @code{&optional} in the parameter list
+indicates that the arguments for subsequent parameters may be omitted
+(omitted parameters default to @code{nil}). Do not write
+@code{&optional} when you call the function.
+
+ The keyword @code{&rest} (which will always be followed by a single
+parameter) indicates that any number of arguments can follow. The value
+of the single following parameter will be a list of all these arguments.
+Do not write @code{&rest} when you call the function.
+
+ Here is a description of an imaginary function @code{foo}:
+
+@defun foo integer1 &optional integer2 &rest integers
+The function @code{foo} subtracts @var{integer1} from @var{integer2},
+then adds all the rest of the arguments to the result. If @var{integer2}
+is not supplied, then the number 19 is used by default.
+
+@example
+(foo 1 5 3 9)
+ @result{} 16
+(foo 5)
+ @result{} 14
+@end example
+
+More generally,
+
+@example
+(foo @var{w} @var{x} @var{y}@dots{})
+@equiv{}
+(+ (- @var{x} @var{w}) @var{y}@dots{})
+@end example
+@end defun
+
+ Any parameter whose name contains the name of a type (e.g.,
+@var{integer}, @var{integer1} or @var{buffer}) is expected to be of that
+type. A plural of a type (such as @var{buffers}) often means a list of
+objects of that type. Parameters named @var{object} may be of any type.
+(@xref{Types of Lisp Object}, for a list of Emacs object types.)
+Parameters with other sorts of names (e.g., @var{new-file}) are
+discussed specifically in the description of the function. In some
+sections, features common to parameters of several functions are
+described at the beginning.
+
+ @xref{Lambda Expressions}, for a more complete description of optional
+and rest arguments.
+
+ Command, macro, and special form descriptions have the same format,
+but the word `Function' is replaced by `Command', `Macro', or `Special
+Form', respectively. Commands are simply functions that may be called
+interactively; macros process their arguments differently from functions
+(the arguments are not evaluated), but are presented the same way.
+
+ Special form descriptions use a more complex notation to specify
+optional and repeated parameters because they can break the argument
+list down into separate arguments in more complicated ways.
+@samp{@code{@r{[}@var{optional-arg}@r{]}}} means that @var{optional-arg} is
+optional and @samp{@var{repeated-args}@dots{}} stands for zero or more
+arguments. Parentheses are used when several arguments are grouped into
+additional levels of list structure. Here is an example:
+
+@defspec count-loop (@var{var} [@var{from} @var{to} [@var{inc}]]) @var{body}@dots{}
+This imaginary special form implements a loop that executes the
+@var{body} forms and then increments the variable @var{var} on each
+iteration. On the first iteration, the variable has the value
+@var{from}; on subsequent iterations, it is incremented by 1 (or by
+@var{inc} if that is given). The loop exits before executing @var{body}
+if @var{var} equals @var{to}. Here is an example:
+
+@example
+(count-loop (i 0 10)
+ (prin1 i) (princ " ")
+ (prin1 (aref vector i)) (terpri))
+@end example
+
+If @var{from} and @var{to} are omitted, then @var{var} is bound to
+@code{nil} before the loop begins, and the loop exits if @var{var} is
+non-@code{nil} at the beginning of an iteration. Here is an example:
+
+@example
+(count-loop (done)
+ (if (pending)
+ (fixit)
+ (setq done t)))
+@end example
+
+In this special form, the arguments @var{from} and @var{to} are
+optional, but must both be present or both absent. If they are present,
+@var{inc} may optionally be specified as well. These arguments are
+grouped with the argument @var{var} into a list, to distinguish them
+from @var{body}, which includes all remaining elements of the form.
+@end defspec
+
+@node A Sample Variable Description
+@subsubsection A Sample Variable Description
+@cindex variable descriptions
+@cindex option descriptions
+
+ A @dfn{variable} is a name that can hold a value. Although any
+variable can be set by the user, certain variables that exist
+specifically so that users can change them are called @dfn{user
+options}. Ordinary variables and user options are described using a
+format like that for functions except that there are no arguments.
+
+ Here is a description of the imaginary @code{electric-future-map}
+variable.@refill
+
+@defvar electric-future-map
+The value of this variable is a full keymap used by Electric Command
+Future mode. The functions in this map allow you to edit commands you
+have not yet thought about executing.
+@end defvar
+
+ User option descriptions have the same format, but `Variable' is
+replaced by `User Option'.
+
+@node Acknowledgements
+@section Acknowledgements
+
+ This manual was written by Robert Krawitz, Bil Lewis, Dan LaLiberte,
+Richard M. Stallman and Chris Welty, the volunteers of the GNU manual
+group, in an effort extending over several years. Robert J. Chassell
+helped to review and edit the manual, with the support of the Defense
+Advanced Research Projects Agency, ARPA Order 6082, arranged by Warren
+A. Hunt, Jr. of Computational Logic, Inc.
+
+ Corrections were supplied by Karl Berry, Jim Blandy, Bard Bloom,
+Stephane Boucher, David Boyes, Alan Carroll, Richard Davis, Lawrence
+R. Dodd, Peter Doornbosch, David A. Duff, Chris Eich, Beverly
+Erlebacher, David Eckelkamp, Ralf Fassel, Eirik Fuller, Stephen Gildea,
+Bob Glickstein, Eric Hanchrow, George Hartzell, Nathan Hess, Masayuki
+Ida, Dan Jacobson, Jak Kirman, Bob Knighten, Frederick M. Korz, Joe
+Lammens, Glenn M. Lewis, K. Richard Magill, Brian Marick, Roland
+McGrath, Skip Montanaro, John Gardiner Myers, Thomas A. Peterson,
+Francesco Potorti, Friedrich Pukelsheim, Arnold D. Robbins, Raul
+Rockwell, Per Starback, Shinichirou Sugou, Kimmo Suominen, Edward Tharp,
+Bill Trost, Rickard Westman, Jean White, Matthew Wilding, Carl Witty,
+Dale Worley, Rusty Wright, and David D. Zuhn.