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INFO-DIR-SECTION XEmacs Editor
START-INFO-DIR-ENTRY
* XEmacs: (xemacs).             XEmacs Editor.
END-INFO-DIR-ENTRY

   This file documents the XEmacs editor.

   Copyright (C) 1985, 1986, 1988 Richard M. Stallman.  Copyright (C)
1991, 1992, 1993, 1994 Lucid, Inc.  Copyright (C) 1993, 1994 Sun
Microsystems, Inc.  Copyright (C) 1995 Amdahl Corporation.

   Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

   Permission is granted to copy and distribute modified versions of
this manual under the conditions for verbatim copying, provided also
that the sections entitled "The GNU Manifesto", "Distribution" and "GNU
General Public License" are included exactly as in the original, and
provided that the entire resulting derived work is distributed under the
terms of a permission notice identical to this one.

   Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions, except that the sections entitled "The GNU Manifesto",
"Distribution" and "GNU General Public License" may be included in a
translation approved by the author instead of in the original English.

\1f
File: xemacs.info,  Node: Pages,  Next: Filling,  Prev: Paragraphs,  Up: Text

Pages
=====

   Files are often thought of as divided into "pages" by the "formfeed"
character (ASCII Control-L, octal code 014).  For example, if a file is
printed on a line printer, each "page" of the file starts on a new page
of paper.  Emacs treats a page-separator character just like any other
character.  It can be inserted with `C-q C-l' or deleted with <DEL>.
You are free to paginate your file or not.  However, since pages are
often meaningful divisions of the file, commands are provided to move
over them and operate on them.

`C-x ['
     Move point to previous page boundary (`backward-page').

`C-x ]'
     Move point to next page boundary (`forward-page').

`C-x C-p'
     Put point and mark around this page (or another page)
     (`mark-page').

`C-x l'
     Count the lines in this page (`count-lines-page').

   The `C-x [' (`backward-page') command moves point to immediately
after the previous page delimiter.  If point is already right after a
page delimiter, the command skips that one and stops at the previous
one.  A numeric argument serves as a repeat count.  The `C-x ]'
(`forward-page') command moves forward past the next page delimiter.

   The `C-x C-p' command (`mark-page') puts point at the beginning of
the current page and the mark at the end.  The page delimiter at the end
is included (the mark follows it).  The page delimiter at the front is
excluded (point follows it).  You can follow this command  by `C-w' to
kill a page you want to move elsewhere.  If you insert the page after a
page delimiter, at a place where `C-x ]' or `C-x [' would take you, the
page will be properly delimited before and after once again.

   A numeric argument to `C-x C-p' is used to specify which page to go
to, relative to the current one.  Zero means the current page.  One
means the next page, and -1 means the previous one.

   The `C-x l' command (`count-lines-page') can help you decide where
to break a page in two.  It prints the total number of lines in the
current page in the echo area, then divides the lines into those
preceding the current line and those following it, for example

     Page has 96 (72+25) lines

Notice that the sum is off by one; this is correct if point is not at
the beginning of a line.

   The variable `page-delimiter' should have as its value a regexp that
matches the beginning of a line that separates pages.  This defines
where pages begin.  The normal value of this variable is `"^\f"', which
matches a formfeed character at the beginning of a line.

\1f
File: xemacs.info,  Node: Filling,  Next: Case,  Prev: Pages,  Up: Text

Filling Text
============

   If you use Auto Fill mode, Emacs "fills" text (breaks it up into
lines that fit in a specified width) as you insert it.  When you alter
existing text it is often no longer be properly filled afterwards and
you can use explicit commands for filling.

* Menu:

* Auto Fill::     Auto Fill mode breaks long lines automatically.
* Fill Commands:: Commands to refill paragraphs and center lines.
* Fill Prefix::   Filling when every line is indented or in a comment, etc.

\1f
File: xemacs.info,  Node: Auto Fill,  Next: Fill Commands,  Prev: Filling,  Up: Filling

Auto Fill Mode
--------------

   "Auto Fill" mode is a minor mode in which lines are broken
automatically when they become too wide.  Breaking happens only when
you type a <SPC> or <RET>.

`M-x auto-fill-mode'
     Enable or disable Auto Fill mode.

`<SPC>'
`<RET>'
     In Auto Fill mode, break lines when appropriate.

   `M-x auto-fill-mode' turns Auto Fill mode on if it was off, or off
if it was on.  With a positive numeric argument the command always turns
Auto Fill mode on, and with a negative argument it always turns it off.
The presence of the word `Fill' in the mode line, inside the
parentheses, indicates that Auto Fill mode is in effect.  Auto Fill mode
is a minor mode; you can turn it on or off for each buffer individually.
*Note Minor Modes::.

   In Auto Fill mode, lines are broken automatically at spaces when
they get longer than desired.  Line breaking and rearrangement takes
place only when you type <SPC> or <RET>.  To insert a space or newline
without permitting line-breaking, type `C-q <SPC>' or `C-q <LFD>'
(recall that a newline is really a linefeed).  `C-o' inserts a newline
without line breaking.

   Auto Fill mode works well with Lisp mode: when it makes a new line in
Lisp mode, it indents that line with <TAB>.  If a line ending in a Lisp
comment gets too long, the text of the comment is split into two
comment lines.  Optionally, new comment delimiters are inserted at the
end of the first line and the beginning of the second, so that each line
is a separate comment.  The variable `comment-multi-line' controls the
choice (*note Comments::.).

   Auto Fill mode does not refill entire paragraphs.  It can break
lines but cannot merge lines.  Editing in the middle of a paragraph can
result in a paragraph that is not correctly filled.  The easiest way to
make the paragraph properly filled again is using an explicit fill
commands.

   Many users like Auto Fill mode and want to use it in all text files.
The section on init files explains how you can arrange this permanently
for yourself.  *Note Init File::.

\1f
File: xemacs.info,  Node: Fill Commands,  Next: Fill Prefix,  Prev: Auto Fill,  Up: Filling

Explicit Fill Commands
----------------------

`M-q'
     Fill current paragraph (`fill-paragraph').

`M-g'
     Fill each paragraph in the region (`fill-region').

`C-x f'
     Set the fill column (`set-fill-column').

`M-x fill-region-as-paragraph'
     Fill the region, considering it as one paragraph.

`M-s'
     Center a line.

   To refill a paragraph, use the command `Meta-q' (`fill-paragraph').
It causes the paragraph containing point, or the one after point if
point is between paragraphs, to be refilled.  All line breaks are
removed, and new ones are inserted where necessary.  `M-q' can be
undone with `C-_'.  *Note Undo::.

   To refill many paragraphs, use `M-g' (`fill-region'), which divides
the region into paragraphs and fills each of them.

   `Meta-q' and `Meta-g' use the same criteria as `Meta-h' for finding
paragraph boundaries (*note Paragraphs::.).  For more control, you can
use `M-x fill-region-as-paragraph', which refills everything between
point and mark.  This command recognizes only blank lines as paragraph
separators.

   A numeric argument to `M-g' or `M-q' causes it to "justify" the text
as well as filling it.  Extra spaces are inserted to make the right
margin line up exactly at the fill column.  To remove the extra spaces,
use `M-q' or `M-g' with no argument.

   The variable `auto-fill-inhibit-regexp' takes as a value a regexp to
match lines that should not be auto-filled.

   The command `Meta-s' (`center-line') centers the current line within
the current fill column.  With an argument, it centers several lines
individually and moves past them.

   The maximum line width for filling is in the variable `fill-column'.
Altering the value of `fill-column' makes it local to the current
buffer; until then, the default value--initially 70--is in effect.
*Note Locals::.

   The easiest way to set `fill-column' is to use the command `C-x f'
(`set-fill-column').  With no argument, it sets `fill-column' to the
current horizontal position of point.  With a numeric argument, it uses
that number as the new fill column.

\1f
File: xemacs.info,  Node: Fill Prefix,  Prev: Fill Commands,  Up: Filling

The Fill Prefix
---------------

   To fill a paragraph in which each line starts with a special marker
(which might be a few spaces, giving an indented paragraph), use the
"fill prefix" feature.  The fill prefix is a string which is not
included in filling.  Emacs expects every line to start with a fill
prefix.

`C-x .'
     Set the fill prefix (`set-fill-prefix').

`M-q'
     Fill a paragraph using current fill prefix (`fill-paragraph').

`M-x fill-individual-paragraphs'
     Fill the region, considering each change of indentation as
     starting a new paragraph.

   To specify a fill prefix, move to a line that starts with the desired
prefix, put point at the end of the prefix, and give the command
`C-x .' (`set-fill-prefix').  That's a period after the `C-x'.  To turn
off the fill prefix, specify an empty prefix: type `C-x .' with point
at the beginning of a line.

   When a fill prefix is in effect, the fill commands remove the fill
prefix from each line before filling and insert it on each line after
filling.  Auto Fill mode also inserts the fill prefix inserted on new
lines it creates.  Lines that do not start with the fill prefix are
considered to start paragraphs, both in `M-q' and the paragraph
commands; this is just right if you are using paragraphs with hanging
indentation (every line indented except the first one).  Lines which are
blank or indented once the prefix is removed also separate or start
paragraphs; this is what you want if you are writing multi-paragraph
comments with a comment delimiter on each line.

   The fill prefix is stored in the variable `fill-prefix'.  Its value
is a string, or `nil' when there is no fill prefix.  This is a
per-buffer variable; altering the variable affects only the current
buffer, but there is a default value which you can change as well.
*Note Locals::.

   Another way to use fill prefixes is through `M-x
fill-individual-paragraphs'.  This function divides the region into
groups of consecutive lines with the same amount and kind of
indentation and fills each group as a paragraph, using its indentation
as a fill prefix.

\1f
File: xemacs.info,  Node: Case,  Prev: Filling,  Up: Text

Case Conversion Commands
========================

   Emacs has commands for converting either a single word or any
arbitrary range of text to upper case or to lower case.

`M-l'
     Convert following word to lower case (`downcase-word').

`M-u'
     Convert following word to upper case (`upcase-word').

`M-c'
     Capitalize the following word (`capitalize-word').

`C-x C-l'
     Convert region to lower case (`downcase-region').

`C-x C-u'
     Convert region to upper case (`upcase-region').

   The word conversion commands are used most frequently.  `Meta-l'
(`downcase-word') converts the word after point to lower case, moving
past it.  Thus, repeating `Meta-l' converts successive words.  `Meta-u'
(`upcase-word') converts to all capitals instead, while `Meta-c'
(`capitalize-word') puts the first letter of the word into upper case
and the rest into lower case.  The word conversion commands convert
several words at once if given an argument.  They are especially
convenient for converting a large amount of text from all upper case to
mixed case: you can move through the text using `M-l', `M-u', or `M-c'
on each word as appropriate, occasionally using `M-f' instead to skip a
word.

   When given a negative argument, the word case conversion commands
apply to the appropriate number of words before point, but do not move
point.  This is convenient when you have just typed a word in the wrong
case: you can give the case conversion command and continue typing.

   If a word case conversion command is given in the middle of a word,
it applies only to the part of the word which follows point.  This is
just like what `Meta-d' (`kill-word') does.  With a negative argument,
case conversion applies only to the part of the word before point.

   The other case conversion commands are `C-x C-u' (`upcase-region')
and `C-x C-l' (`downcase-region'), which convert everything between
point and mark to the specified case.  Point and mark do not move.

\1f
File: xemacs.info,  Node: Programs,  Next: Running,  Prev: Text,  Up: Top

Editing Programs
****************

   Emacs has many commands designed to understand the syntax of
programming languages such as Lisp and C.  These commands can:

   * Move over or kill balanced expressions or "sexps" (*note Lists::.).

   * Move over or mark top-level balanced expressions ("defuns", in
     Lisp; functions, in C).

   * Show how parentheses balance (*note Matching::.).

   * Insert, kill, or align comments (*note Comments::.).

   * Follow the usual indentation conventions of the language (*note
     Grinding::.).

   The commands available for words, sentences, and paragraphs are
useful in editing code even though their canonical application is for
editing human language text.  Most symbols contain words (*note
Words::.); sentences can be found in strings and comments (*note
Sentences::.).  Paragraphs per se are not present in code, but the
paragraph commands are useful anyway, because Lisp mode and C mode
define paragraphs to begin and end at blank lines (*note
Paragraphs::.).  Judicious use of blank lines to make the program
clearer also provides interesting chunks of text for the paragraph
commands to work on.

   The selective display feature is useful for looking at the overall
structure of a function (*note Selective Display::.).  This feature
causes only the lines that are indented less than a specified amount to
appear on the screen.

* Menu:

* Program Modes::       Major modes for editing programs.
* Lists::               Expressions with balanced parentheses.
                         There are editing commands to operate on them.
* Defuns::              Each program is made up of separate functions.
                         There are editing commands to operate on them.
* Grinding::            Adjusting indentation to show the nesting.
* Matching::            Insertion of a close-delimiter flashes matching open.
* Comments::            Inserting, illing and aligning comments.
* Balanced Editing::    Inserting two matching parentheses at once, etc.
* Lisp Completion::     Completion on symbol names in Lisp code.
* Documentation::       Getting documentation of functions you plan to call.
* Change Log::          Maintaining a change history for your program.
* Tags::                Go direct to any function in your program in one
                         command.  Tags remembers which file it is in.
* Fortran::             Fortran mode and its special features.
* Asm Mode::            Asm mode and its special features.

\1f
File: xemacs.info,  Node: Program Modes,  Next: Lists,  Prev: Programs,  Up: Programs

Major Modes for Programming Languages
=====================================

   Emacs has several major modes for the programming languages Lisp,
Scheme (a variant of Lisp), C, Fortran, and Muddle.  Ideally, a major
mode should be implemented for each programming language you might want
to edit with Emacs; but often the mode for one language can serve for
other syntactically similar languages.  The language modes that exist
are those that someone decided to take the trouble to write.

   There are several variants of Lisp mode, which differ in the way they
interface to Lisp execution.  *Note Lisp Modes::.

   Each of the programming language modes defines the <TAB> key to run
an indentation function that knows the indentation conventions of that
language and updates the current line's indentation accordingly.  For
example, in C mode <TAB> is bound to `c-indent-line'.  <LFD> is
normally defined to do <RET> followed by <TAB>; thus it, too, indents
in a mode-specific fashion.

   In most programming languages, indentation is likely to vary from
line to line.  So the major modes for those languages rebind <DEL> to
treat a tab as if it were the equivalent number of spaces (using the
command `backward-delete-char-untabify').  This makes it possible to
rub out indentation one column at a time without worrying whether it is
made up of spaces or tabs.  In these modes, use `C-b C-d' to delete a
tab character before point.

   Programming language modes define paragraphs to be separated only by
blank lines, so that the paragraph commands remain useful.  Auto Fill
mode, if enabled in a programming language major mode, indents the new
lines which it creates.

   Turning on a major mode calls a user-supplied function called the
"mode hook", which is the value of a Lisp variable.  For example,
turning on C mode calls the value of the variable `c-mode-hook' if that
value exists and is non-`nil'.  Mode hook variables for other
programming language modes include `lisp-mode-hook',
`emacs-lisp-mode-hook', `lisp-interaction-mode-hook',
`scheme-mode-hook', and `muddle-mode-hook'.  The mode hook function
receives no arguments.

\1f
File: xemacs.info,  Node: Lists,  Next: Defuns,  Prev: Program Modes,  Up: Programs

Lists and Sexps
===============

   By convention, Emacs keys for dealing with balanced expressions are
usually `Control-Meta-' characters.  They tend to be analogous in
function to their `Control-' and `Meta-' equivalents.  These commands
are usually thought of as pertaining to expressions in programming
languages, but can be useful with any language in which some sort of
parentheses exist (including English).

   The commands fall into two classes.  Some commands deal only with
"lists" (parenthetical groupings).  They see nothing except
parentheses, brackets, braces (depending on what must balance in the
language you are working with), and escape characters that might be used
to quote those.

   The other commands deal with expressions or "sexps".  The word `sexp'
is derived from "s-expression", the term for a symbolic expression in
Lisp.  In Emacs, the notion of `sexp' is not limited to Lisp.  It
refers to an expression in the language  your program is written in.
Each programming language has its own major mode, which customizes the
syntax tables so that expressions in that language count as sexps.

   Sexps typically include symbols, numbers, and string constants, as
well as anything contained in parentheses, brackets, or braces.

   In languages that use prefix and infix operators, such as C, it is
not possible for all expressions to be sexps.  For example, C mode does
not recognize `foo + bar' as an sexp, even though it is a C expression;
it recognizes `foo' as one sexp and `bar' as another, with the `+' as
punctuation between them.  This is a fundamental ambiguity: both `foo +
bar' and `foo' are legitimate choices for the sexp to move over if
point is at the `f'.  Note that `(foo + bar)' is a sexp in C mode.

   Some languages have obscure forms of syntax for expressions that
nobody has bothered to make Emacs understand properly.

`C-M-f'
     Move forward over an sexp (`forward-sexp').

`C-M-b'
     Move backward over an sexp (`backward-sexp').

`C-M-k'
     Kill sexp forward (`kill-sexp').

`C-M-u'
     Move up and backward in list structure (`backward-up-list').

`C-M-d'
     Move down and forward in list structure (`down-list').

`C-M-n'
     Move forward over a list (`forward-list').

`C-M-p'
     Move backward over a list (`backward-list').

`C-M-t'
     Transpose expressions (`transpose-sexps').

`C-M-@'
     Put mark after following expression (`mark-sexp').

   To move forward over an sexp, use `C-M-f' (`forward-sexp').  If the
first significant character after point is an opening delimiter (`(' in
Lisp; `(', `[', or `{' in C), `C-M-f' moves past the matching closing
delimiter.  If the character begins a symbol, string, or number,
`C-M-f' moves over that.  If the character after point is a closing
delimiter, `C-M-f' just moves past it.  (This last is not really moving
across an sexp; it is an exception which is included in the definition
of `C-M-f' because it is as useful a behavior as anyone can think of
for that situation.)

   The command `C-M-b' (`backward-sexp') moves backward over a sexp.
The detailed rules are like those above for `C-M-f', but with
directions reversed.  If there are any prefix characters (single quote,
back quote, and comma, in Lisp) preceding the sexp, `C-M-b' moves back
over them as well.

   `C-M-f' or `C-M-b' with an argument repeats that operation the
specified number of times; with a negative argument, it moves in the
opposite direction.

   In languages such as C where the comment-terminator can be
recognized, the sexp commands move across comments as if they were
whitespace.  In Lisp and other languages where comments run until the
end of a line, it is very difficult to ignore comments when parsing
backwards; therefore, in such languages the sexp commands treat the
text of comments as if it were code.

   Killing an sexp at a time can be done with `C-M-k' (`kill-sexp').
`C-M-k' kills the characters that `C-M-f' would move over.

   The "list commands", `C-M-n' (`forward-list') and `C-M-p'
(`backward-list'), move over lists like the sexp commands but skip over
any number of other kinds of sexps (symbols, strings, etc).  In some
situations, these commands are useful because they usually ignore
comments, since the comments usually do not contain any lists.

   `C-M-n' and `C-M-p' stay at the same level in parentheses, when that
is possible.  To move up one (or N) levels, use `C-M-u'
(`backward-up-list').  `C-M-u' moves backward up past one unmatched
opening delimiter.  A positive argument serves as a repeat count; a
negative argument reverses direction of motion and also requests
repetition, so it moves forward and up one or more levels.

   To move down in list structure, use `C-M-d' (`down-list').  In Lisp
mode, where `(' is the only opening delimiter, this is nearly the same
as searching for a `('.  An argument specifies the number of levels of
parentheses to go down.

   `C-M-t' (`transpose-sexps') drags the previous sexp across the next
one.  An argument serves as a repeat count, and a negative argument
drags backwards (thus canceling out the effect of `C-M-t' with a
positive argument).  An argument of zero, rather than doing nothing,
transposes the sexps ending after point and the mark.

   To make the region be the next sexp in the buffer, use `C-M-@'
(`mark-sexp') which sets the mark at the same place that `C-M-f' would
move to.  `C-M-@' takes arguments like `C-M-f'.  In particular, a
negative argument is useful for putting the mark at the beginning of
the previous sexp.

   The list and sexp commands' understanding of syntax is completely
controlled by the syntax table.  Any character can, for example, be
declared to be an opening delimiter and act like an open parenthesis.
*Note Syntax::.

\1f
File: xemacs.info,  Node: Defuns,  Next: Grinding,  Prev: Lists,  Up: Programs

Defuns
======

   In Emacs, a parenthetical grouping at the top level in the buffer is
called a "defun".  The name derives from the fact that most top-level
lists in Lisp are instances of the special form `defun', but Emacs
calls any top-level parenthetical grouping counts a defun regardless of
its contents or the programming language.  For example, in C, the body
of a function definition is a defun.

`C-M-a'
     Move to beginning of current or preceding defun
     (`beginning-of-defun').

`C-M-e'
     Move to end of current or following defun (`end-of-defun').

`C-M-h'
     Put region around whole current or following defun (`mark-defun').

   The commands to move to the beginning and end of the current defun
are `C-M-a' (`beginning-of-defun') and `C-M-e' (`end-of-defun').

   To operate on the current defun, use `C-M-h' (`mark-defun') which
puts point at the beginning and the mark at the end of the current or
next defun.  This is the easiest way to prepare for moving the defun to
a different place.  In C mode, `C-M-h' runs the function
`mark-c-function', which is almost the same as `mark-defun', but which
backs up over the argument declarations, function name, and returned
data type so that the entire C function is inside the region.

   To compile and evaluate the current defun, use `M-x compile-defun'.
This function prints the results in the minibuffer. If you include an
argument, it inserts the value in the current buffer after the defun.

   Emacs assumes that any open-parenthesis found in the leftmost column
is the start of a defun.  Therefore, never put an open-parenthesis at
the left margin in a Lisp file unless it is the start of a top level
list.  Never put an open-brace or other opening delimiter at the
beginning of a line of C code unless it starts the body of a function.
The most likely problem case is when you want an opening delimiter at
the start of a line inside a string.  To avoid trouble, put an escape
character (`\' in C and Emacs Lisp, `/' in some other Lisp dialects)
before the opening delimiter.  It will not affect the contents of the
string.

   The original Emacs found defuns by moving upward a level of
parentheses until there were no more levels to go up.  This required
scanning back to the beginning of the buffer for every function.  To
speed this up, Emacs was changed to assume that any `(' (or other
character assigned the syntactic class of opening-delimiter) at the
left margin is the start of a defun.  This heuristic is nearly always
right; however, it mandates the convention described above.

\1f
File: xemacs.info,  Node: Grinding,  Next: Matching,  Prev: Defuns,  Up: Programs

Indentation for Programs
========================

   The best way to keep a program properly indented ("ground") is to
use Emacs to re-indent it as you change the program.  Emacs has commands
to indent properly either a single line, a specified number of lines, or
all of the lines inside a single parenthetical grouping.

* Menu:

* Basic Indent::
* Multi-line Indent::   Commands to reindent many lines at once.
* Lisp Indent::         Specifying how each Lisp function should be indented.
* C Indent::            Choosing an indentation style for C code.

\1f
File: xemacs.info,  Node: Basic Indent,  Next: Multi-line Indent,  Prev: Grinding,  Up: Grinding

Basic Program Indentation Commands
----------------------------------

`<TAB>'
     Adjust indentation of current line.

`<LFD>'
     Equivalent to <RET> followed by <TAB> (`newline-and-indent').

   The basic indentation command is <TAB>, which gives the current line
the correct indentation as determined from the previous lines.  The
function that <TAB> runs depends on the major mode; it is
`lisp-indent-line' in Lisp mode, `c-indent-line' in C mode, etc.  These
functions understand different syntaxes for different languages, but
they all do about the same thing.  <TAB> in any programming language
major mode inserts or deletes whitespace at the beginning of the
current line, independent of where point is in the line.  If point is
inside the whitespace at the beginning of the line, <TAB> leaves it at
the end of that whitespace; otherwise, <TAB> leaves point fixed with
respect to the characters around it.

   Use `C-q <TAB>' to insert a tab at point.

   When entering a large amount of new code, use <LFD>
(`newline-and-indent'), which is equivalent to a <RET> followed by a
<TAB>.  <LFD> creates a blank line, then gives it the appropriate
indentation.

   <TAB> indents the second and following lines of the body of a
parenthetical grouping each under the preceding one; therefore, if you
alter one line's indentation to be nonstandard, the lines below tend to
follow it.  This is the right behavior in cases where the standard
result of <TAB> does not look good.

   Remember that Emacs assumes that an open-parenthesis, open-brace, or
other opening delimiter at the left margin (including the indentation
routines) is the start of a function.  You should therefore never have
an opening delimiter in column zero that is not the beginning of a
function, not even inside a string.  This restriction is vital for
making the indentation commands fast. *Note Defuns::, for more
information on this behavior.

\1f
File: xemacs.info,  Node: Multi-line Indent,  Next: Lisp Indent,  Prev: Basic Indent,  Up: Grinding

Indenting Several Lines
-----------------------

   Several commands are available to re-indent several lines of code
which have been altered or moved to a different level in a list
structure.

`C-M-q'
     Re-indent all the lines within one list (`indent-sexp').

`C-u <TAB>'
     Shift an entire list rigidly sideways so that its first line is
     properly indented.

`C-M-\'
     Re-indent all lines in the region (`indent-region').

   To re-indent the contents of a single list, position point before the
beginning of it and type `C-M-q'. This key is bound to `indent-sexp' in
Lisp mode, `indent-c-exp' in C mode, and bound to other suitable
functions in other modes.  The indentation of the line the sexp starts
on is not changed; therefore, only the relative indentation within the
list, and not its position, is changed.  To correct the position as
well, type a <TAB> before `C-M-q'.

   If the relative indentation within a list is correct but the
indentation of its beginning is not, go to the line on which the list
begins and type `C-u <TAB>'.  When you give <TAB> a numeric argument,
it moves all the lines in the group, starting on the current line,
sideways the same amount that the current line moves.  The command does
not move lines that start inside strings, or C preprocessor lines when
in C mode.

   Another way to specify a range to be re-indented is with point and
mark.  The command `C-M-\' (`indent-region') applies <TAB> to every
line whose first character is between point and mark.

\1f
File: xemacs.info,  Node: Lisp Indent,  Next: C Indent,  Prev: Multi-line Indent,  Up: Grinding

Customizing Lisp Indentation
----------------------------

   The indentation pattern for a Lisp expression can depend on the
function called by the expression.  For each Lisp function, you can
choose among several predefined patterns of indentation, or define an
arbitrary one with a Lisp program.

   The standard pattern of indentation is as follows: the second line
of the expression is indented under the first argument, if that is on
the same line as the beginning of the expression; otherwise, the second
line is indented underneath the function name.  Each following line is
indented under the previous line whose nesting depth is the same.

   If the variable `lisp-indent-offset' is non-`nil', it overrides the
usual indentation pattern for the second line of an expression, so that
such lines are always indented `lisp-indent-offset' more columns than
the containing list.

   Certain functions override the standard pattern.  Functions whose
names start with `def' always indent the second line by
`lisp-body-indention' extra columns beyond the open-parenthesis
starting the expression.

   Individual functions can override the standard pattern in various
ways, according to the `lisp-indent-function' property of the function
name.  (Note: `lisp-indent-function' was formerly called
`lisp-indent-hook').  There are four possibilities for this property:

`nil'
     This is the same as no property; the standard indentation pattern
     is used.

`defun'
     The pattern used for function names that start with `def' is used
     for this function also.

a number, NUMBER
     The first NUMBER arguments of the function are "distinguished"
     arguments; the rest are considered the "body" of the expression.
     A line in the expression is indented according to whether the
     first argument on it is distinguished or not.  If the argument is
     part of the body, the line is indented `lisp-body-indent' more
     columns than the open-parenthesis starting the containing
     expression.  If the argument is distinguished and is either the
     first or second argument, it is indented twice that many extra
     columns.  If the argument is distinguished and not the first or
     second argument, the standard pattern is followed for that line.

a symbol, SYMBOL
     SYMBOL should be a function name; that function is called to
     calculate the indentation of a line within this expression.  The
     function receives two arguments:
    STATE
          The value returned by `parse-partial-sexp' (a Lisp primitive
          for indentation and nesting computation) when it parses up to
          the beginning of this line.

    POS
          The position at which the line being indented begins.

     It should return either a number, which is the number of columns of
     indentation for that line, or a list whose first element is such a
     number.  The difference between returning a number and returning a
     list is that a number says that all following lines at the same
     nesting level should be indented just like this one; a list says
     that following lines might call for different indentations.  This
     makes a difference when the indentation is computed by `C-M-q'; if
     the value is a number, `C-M-q' need not recalculate indentation
     for the following lines until the end of the list.

\1f
File: xemacs.info,  Node: C Indent,  Prev: Lisp Indent,  Up: Grinding

Customizing C Indentation
-------------------------

   Two variables control which commands perform C indentation and when.

   If `c-auto-newline' is non-`nil', newlines are inserted both before
and after braces that you insert and after colons and semicolons.
Correct C indentation is done on all the lines that are made this way.

   If `c-tab-always-indent' is non-`nil', the <TAB> command in C mode
does indentation only if point is at the left margin or within the
line's indentation.  If there is non-whitespace to the left of point,
<TAB> just inserts a tab character in the buffer.  Normally, this
variable is `nil', and <TAB> always reindents the current line.

   C does not have anything analogous to particular function names for
which special forms of indentation are desirable.  However, it has a
different need for customization facilities: many different styles of C
indentation are in common use.

   There are six variables you can set to control the style that Emacs C
mode will use.

`c-indent-level'
     Indentation of C statements within surrounding block.  The
     surrounding block's indentation is the indentation of the line on
     which the open-brace appears.

`c-continued-statement-offset'
     Extra indentation given to a substatement, such as the then-clause
     of an `if' or body of a `while'.

`c-brace-offset'
     Extra indentation for lines that start with an open brace.

`c-brace-imaginary-offset'
     An open brace following other text is treated as if it were this
     far to the right of the start of its line.

`c-argdecl-indent'
     Indentation level of declarations of C function arguments.

`c-label-offset'
     Extra indentation for a line that is a label, case, or default.

   The variable `c-indent-level' controls the indentation for C
statements with respect to the surrounding block.  In the example:

         {
           foo ();

the difference in indentation between the lines is `c-indent-level'.
Its standard value is 2.

   If the open-brace beginning the compound statement is not at the
beginning of its line, the `c-indent-level' is added to the indentation
of the line, not the column of the open-brace.  For example,

     if (losing) {
       do_this ();

One popular indentation style is that which results from setting
`c-indent-level' to 8 and putting open-braces at the end of a line in
this way.  Another popular style prefers to put the open-brace on a
separate line.

   In fact, the value of the variable `c-brace-imaginary-offset' is
also added to the indentation of such a statement.  Normally this
variable is zero.  Think of this variable as the imaginary position of
the open brace, relative to the first non-blank character on the line.
By setting the variable to 4 and `c-indent-level' to 0, you can get
this style:

     if (x == y) {
         do_it ();
         }

   When `c-indent-level' is zero, the statements inside most braces
line up exactly under the open brace.  An exception are braces in column
zero, like those surrounding a function's body.  The statements inside
those braces are not placed at column zero.  Instead, `c-brace-offset'
and `c-continued-statement-offset' (see below) are added to produce a
typical offset between brace levels, and the statements are indented
that far.

   `c-continued-statement-offset' controls the extra indentation for a
line that starts within a statement (but not within parentheses or
brackets).  These lines are usually statements inside other statements,
like the then-clauses of `if' statements and the bodies of `while'
statements.  The `c-continued-statement-offset' parameter determines
the difference in indentation between the two lines in:

     if (x == y)
       do_it ();

The default value for `c-continued-statement-offset' is 2.  Some
popular indentation styles correspond to a value of zero for
`c-continued-statement-offset'.

   `c-brace-offset' is the extra indentation given to a line that
starts with an open-brace.  Its standard value is zero; compare:

     if (x == y)
       {

with:

     if (x == y)
       do_it ();

If you set `c-brace-offset' to 4, the first example becomes:

     if (x == y)
           {

   `c-argdecl-indent' controls the indentation of declarations of the
arguments of a C function.  It is absolute: argument declarations
receive exactly `c-argdecl-indent' spaces.  The standard value is 5 and
results in code like this:

     char *
     index (string, char)
          char *string;
          int char;

   `c-label-offset' is the extra indentation given to a line that
contains a label, a case statement, or a `default:' statement.  Its
standard value is -2 and results in code like this:

     switch (c)
       {
       case 'x':

If `c-label-offset' were zero, the same code would be indented as:

     switch (c)
       {
         case 'x':

This example assumes that the other variables above also have their
default values.

   Using the indentation style produced by the default settings of the
variables just discussed and putting open braces on separate lines
produces clear and readable files.  For an example, look at any of the C
source files of XEmacs.

\1f
File: xemacs.info,  Node: Matching,  Next: Comments,  Prev: Grinding,  Up: Programs

Automatic Display of Matching Parentheses
=========================================

   The Emacs parenthesis-matching feature shows you automatically how
parentheses match in the text.  Whenever a self-inserting character that
is a closing delimiter is typed, the cursor moves momentarily to the
location of the matching opening delimiter, provided that is visible on
the screen.  If it is not on the screen, some text starting with that
opening delimiter is displayed in the echo area.  Either way, you see
the grouping you are closing off.

   In Lisp, automatic matching applies only to parentheses.  In C, it
also applies to braces and brackets.  Emacs knows which characters to
regard as matching delimiters based on the syntax table set by the major
mode.  *Note Syntax::.

   If the opening delimiter and closing delimiter are mismatched--as in
`[x)'--the echo area displays a warning message.  The correct matches
are specified in the syntax table.

   Two variables control parenthesis matching displays.
`blink-matching-paren' turns the feature on or off. The default is `t'
(match display is on); `nil' turns it off.
`blink-matching-paren-distance' specifies how many characters back
Emacs searches to find a matching opening delimiter.  If the match is
not found in the specified region, scanning stops, and nothing is
displayed.  This prevents wasting lots of time scanning when there is no
match.  The default is 4000.

\1f
File: xemacs.info,  Node: Comments,  Next: Balanced Editing,  Prev: Matching,  Up: Programs

Manipulating Comments
=====================

   The comment commands insert, kill and align comments.

`M-;'
     Insert or align comment (`indent-for-comment').

`C-x ;'
     Set comment column (`set-comment-column').

`C-u - C-x ;'
     Kill comment on current line (`kill-comment').

`M-<LFD>'
     Like <RET> followed by inserting and aligning a comment
     (`indent-new-comment-line').

   The command that creates a comment is `Meta-;'
(`indent-for-comment').  If there is no comment already on the line, a
new comment is created and aligned at a specific column called the
"comment column".  Emacs creates the comment by inserting the string at
the value of `comment-start'; see below.  Point is left after that
string.  If the text of the line extends past the comment column,
indentation is done to a suitable boundary (usually, at least one space
is inserted).  If the major mode has specified a string to terminate
comments, that string is inserted after point, to keep the syntax valid.

   You can also use `Meta-;' to align an existing comment.  If a line
already contains the string that starts comments, `M-;' just moves
point after it and re-indents it to the conventional place.  Exception:
comments starting in column 0 are not moved.

   Some major modes have special rules for indenting certain kinds of
comments in certain contexts.  For example, in Lisp code, comments which
start with two semicolons are indented as if they were lines of code,
instead of at the comment column.  Comments which start with three
semicolons are supposed to start at the left margin.  Emacs understands
these conventions by indenting a double-semicolon comment using <TAB>
and by not changing the indentation of a triple-semicolon comment at
all.

     ;; This function is just an example.
     ;;; Here either two or three semicolons are appropriate.
     (defun foo (x)
     ;;; And now, the first part of the function:
       ;; The following line adds one.
       (1+ x))           ; This line adds one.

   In C code, a comment preceded on its line by nothing but whitespace
is indented like a line of code.

   Even when an existing comment is properly aligned, `M-;' is still
useful for moving directly to the start of the comment.

   `C-u - C-x ;' (`kill-comment') kills the comment on the current
line, if there is one.  The indentation before the start of the comment
is killed as well.  If there does not appear to be a comment in the
line, nothing happens.  To reinsert the comment on another line, move
to the end of that line, type first `C-y', and then `M-;' to realign
the comment.  Note that `C-u - C-x ;' is not a distinct key; it is `C-x
;' (`set-comment-column') with a negative argument.  That command is
programmed to call `kill-comment' when called with a negative argument.
However, `kill-comment' is a valid command which you could bind
directly to a key if you wanted to.

Multiple Lines of Comments
--------------------------

   If you are typing a comment and want to continue it on another line,
use the command `Meta-<LFD>' (`indent-new-comment-line'), which
terminates the comment you are typing, creates a new blank line
afterward, and begins a new comment indented under the old one.  If
Auto Fill mode is on and you go past the fill column while typing, the
comment is continued in just this fashion.  If point is not at the end
of the line when you type `M-<LFD>', the text on the rest of the line
becomes part of the new comment line.

Options Controlling Comments
----------------------------

   The comment column is stored in the variable `comment-column'.  You
can explicitly set it to a number.  Alternatively, the command `C-x ;'
(`set-comment-column') sets the comment column to the column point is
at.  `C-u C-x ;' sets the comment column to match the last comment
before point in the buffer, and then calls `Meta-;' to align the
current line's comment under the previous one.  Note that `C-u - C-x ;'
runs the function `kill-comment' as described above.

   `comment-column' is a per-buffer variable; altering the variable
affects only the current buffer.  You can also change the default value.
*Note Locals::.  Many major modes initialize this variable for the
current buffer.

   The comment commands recognize comments based on the regular
expression that is the value of the variable `comment-start-skip'.
This regexp should not match the null string.  It may match more than
the comment starting delimiter in the strictest sense of the word; for
example, in C mode the value of the variable is `"/\\*+ *"', which
matches extra stars and spaces after the `/*' itself.  (Note that `\\'
is needed in Lisp syntax to include a `\' in the string, which is needed
to deny the first star its special meaning in regexp syntax.  *Note
Regexps::.)

   When a comment command makes a new comment, it inserts the value of
`comment-start' to begin it.  The value of `comment-end' is inserted
after point and will follow the text you will insert into the comment.
In C mode, `comment-start' has the value `"/* "' and `comment-end' has
the value `" */"'.

   `comment-multi-line' controls how `M-<LFD>'
(`indent-new-comment-line') behaves when used inside a comment.  If
`comment-multi-line' is `nil', as it normally is, then `M-<LFD>'
terminates the comment on the starting line and starts a new comment on
the new following line.  If `comment-multi-line' is not `nil', then
`M-<LFD>' sets up the new following line as part of the same comment
that was found on the starting line.  This is done by not inserting a
terminator on the old line and not inserting a starter on the new line.
In languages where multi-line comments are legal, the value you choose
for this variable is a matter of taste.

   The variable `comment-indent-hook' should contain a function that is
called to compute the indentation for a newly inserted comment or for
aligning an existing comment.  Major modes set this variable
differently.  The function is called with no arguments, but with point
at the beginning of the comment, or at the end of a line if a new
comment is to be inserted.  The function should return the column in
which the comment ought to start.  For example, in Lisp mode, the
indent hook function bases its decision on the number of semicolons
that begin an existing comment and on the code in the preceding lines.

\1f
File: xemacs.info,  Node: Balanced Editing,  Next: Lisp Completion,  Prev: Comments,  Up: Programs

Editing Without Unbalanced Parentheses
======================================

`M-('
     Put parentheses around next sexp(s) (`insert-parentheses').

`M-)'
     Move past next close parenthesis and re-indent
     (`move-over-close-and-reindent').

   The commands `M-(' (`insert-parentheses') and `M-)'
(`move-over-close-and-reindent') are designed to facilitate a style of
editing which keeps parentheses balanced at all times.  `M-(' inserts a
pair of parentheses, either together as in `()', or, if given an
argument, around the next several sexps, and leaves point after the open
parenthesis.  Instead of typing `( F O O )', you can type `M-( F O O',
which has the same effect except for leaving the cursor before the
close parenthesis.  You can then type `M-)', which moves past the close
parenthesis, deletes any indentation preceding it (in this example
there is none), and indents with <LFD> after it.

\1f
File: xemacs.info,  Node: Lisp Completion,  Next: Documentation,  Prev: Balanced Editing,  Up: Programs

Completion for Lisp Symbols
===========================

   Completion usually happens in the minibuffer.  An exception is
completion for Lisp symbol names, which is available in all buffers.

   The command `M-<TAB>' (`lisp-complete-symbol') takes the partial
Lisp symbol before point to be an abbreviation, and compares it against
all non-trivial Lisp symbols currently known to Emacs.  Any additional
characters that they all have in common are inserted at point.
Non-trivial symbols are those that have function definitions, values, or
properties.

   If there is an open-parenthesis immediately before the beginning of
the partial symbol, only symbols with function definitions are
considered as completions.

   If the partial name in the buffer has more than one possible
completion and they have no additional characters in common, a list of
all possible completions is displayed in another window.

\1f
File: xemacs.info,  Node: Documentation,  Next: Change Log,  Prev: Lisp Completion,  Up: Programs

Documentation Commands
======================

   As you edit Lisp code to be run in Emacs, you can use the commands
`C-h f' (`describe-function') and `C-h v' (`describe-variable') to
print documentation of functions and variables you want to call.  These
commands use the minibuffer to read the name of a function or variable
to document, and display the documentation in a window.

   For extra convenience, these commands provide default arguments
based on the code in the neighborhood of point.  `C-h f' sets the
default to the function called in the innermost list containing point.
`C-h v' uses the symbol name around or adjacent to point as its default.

   The `M-x manual-entry' command gives you access to documentation on
Unix commands, system calls, and libraries.  The command reads a topic
as an argument, and displays the Unix manual page for that topic.
`manual-entry' always searches all 8 sections of the manual and
concatenates all the entries it finds.  For example, the topic
`termcap' finds the description of the termcap library from section 3,
followed by the description of the termcap data base from section 5.