This is ../info/emacs, produced by makeinfo version 4.0 from emacs.texi.
This is the thirteenth edition of the `GNU Emacs Manual', updated
for Emacs version 20.7.
INFO-DIR-SECTION Editors
START-INFO-DIR-ENTRY
* Emacs: (emacs). The extensible self-documenting text editor.
END-INFO-DIR-ENTRY
Published by the Free Software Foundation 59 Temple Place, Suite 330
Boston, MA 02111-1307 USA
Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995, 1996, 1997, 1998,
1999 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of this
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General Public License" are included exactly as in the original, and
provided that the entire resulting derived work is distributed under the
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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 Free Software Foundation instead of in the
original English.
File: emacs, Node: Format Faces, Next: Format Colors, Prev: Editing Format Info, Up: Formatted Text
Faces in Formatted Text
-----------------------
The Faces submenu lists various Emacs faces including `bold',
`italic', and `underline'. Selecting one of these adds the chosen face
to the region. *Note Faces::. You can also specify a face with these
keyboard commands:
`M-g d'
Set the region, or the next inserted character, to the `default'
face (`facemenu-set-default').
`M-g b'
Set the region, or the next inserted character, to the `bold' face
(`facemenu-set-bold').
`M-g i'
Set the region, or the next inserted character, to the `italic'
face (`facemenu-set-italic').
`M-g l'
Set the region, or the next inserted character, to the
`bold-italic' face (`facemenu-set-bold-italic').
`M-g u'
Set the region, or the next inserted character, to the `underline'
face (`facemenu-set-underline').
`M-g o FACE <RET>'
Set the region, or the next inserted character, to the face FACE
(`facemenu-set-face').
If you use these commands with a prefix argument--or, in Transient
Mark mode, if the region is not active--then these commands specify a
face to use for your next self-inserting input. *Note Transient
Mark::. This applies to both the keyboard commands and the menu
commands.
Enriched mode defines two additional faces: `excerpt' and `fixed'.
These correspond to codes used in the text/enriched file format.
The `excerpt' face is intended for quotations. This face is the
same as `italic' unless you customize it (*note Face Customization::).
The `fixed' face is meant to say, "Use a fixed-width font for this
part of the text." Emacs currently supports only fixed-width fonts;
therefore, the `fixed' annotation is not necessary now. However, we
plan to support variable width fonts in future Emacs versions, and
other systems that display text/enriched format may not use a
fixed-width font as the default. So if you specifically want a certain
part of the text to use a fixed-width font, you should specify the
`fixed' face for that part.
The `fixed' face is normally defined to use a different font from
the default. However, different systems have different fonts installed,
so you may need to customize this.
If your terminal cannot display different faces, you will not be able
to see them, but you can still edit documents containing faces. You can
even add faces and colors to documents. They will be visible when the
file is viewed on a terminal that can display them.
File: emacs, Node: Format Colors, Next: Format Indentation, Prev: Format Faces, Up: Formatted Text
Colors in Formatted Text
------------------------
You can specify foreground and background colors for portions of the
text. There is a menu for specifying the foreground color and a menu
for specifying the background color. Each color menu lists all the
colors that you have used in Enriched mode in the current Emacs session.
If you specify a color with a prefix argument--or, in Transient Mark
mode, if the region is not active--then it applies to your next
self-inserting input. *Note Transient Mark::. Otherwise, the command
applies to the region.
Each color menu contains one additional item: `Other'. You can use
this item to specify a color that is not listed in the menu; it reads
the color name with the minibuffer. To display list of available colors
and their names, use the `Display Colors' menu item in the Text
Properties menu (*note Editing Format Info::).
Any color that you specify in this way, or that is mentioned in a
formatted text file that you read in, is added to both color menus for
the duration of the Emacs session.
There are no key bindings for specifying colors, but you can do so
with the extended commands `M-x facemenu-set-foreground' and `M-x
facemenu-set-background'. Both of these commands read the name of the
color with the minibuffer.
File: emacs, Node: Format Indentation, Next: Format Justification, Prev: Format Colors, Up: Formatted Text
Indentation in Formatted Text
-----------------------------
When editing formatted text, you can specify different amounts of
indentation for the right or left margin of an entire paragraph or a
part of a paragraph. The margins you specify automatically affect the
Emacs fill commands (*note Filling::) and line-breaking commands.
The Indentation submenu provides a convenient interface for
specifying these properties. The submenu contains four items:
`Indent More'
Indent the region by 4 columns (`increase-left-margin'). In
Enriched mode, this command is also available on `C-x <TAB>'; if
you supply a numeric argument, that says how many columns to add
to the margin (a negative argument reduces the number of columns).
`Indent Less'
Remove 4 columns of indentation from the region.
`Indent Right More'
Make the text narrower by indenting 4 columns at the right margin.
`Indent Right Less'
Remove 4 columns of indentation from the right margin.
You can use these commands repeatedly to increase or decrease the
indentation.
The most common way to use these commands is to change the
indentation of an entire paragraph. However, that is not the only use.
You can change the margins at any point; the new values take effect at
the end of the line (for right margins) or the beginning of the next
line (for left margins).
This makes it possible to format paragraphs with "hanging indents",
which means that the first line is indented less than subsequent lines.
To set up a hanging indent, increase the indentation of the region
starting after the first word of the paragraph and running until the end
of the paragraph.
Indenting the first line of a paragraph is easier. Set the margin
for the whole paragraph where you want it to be for the body of the
paragraph, then indent the first line by inserting extra spaces or tabs.
Sometimes, as a result of editing, the filling of a paragraph becomes
messed up--parts of the paragraph may extend past the left or right
margins. When this happens, use `M-q' (`fill-paragraph') to refill the
paragraph.
The variable `standard-indent' specifies how many columns these
commands should add to or subtract from the indentation. The default
value is 4. The overall default right margin for Enriched mode is
controlled by the variable `fill-column', as usual.
The fill prefix, if any, works in addition to the specified paragraph
indentation: `C-x .' does not include the specified indentation's
whitespace in the new value for the fill prefix, and the fill commands
look for the fill prefix after the indentation on each line. *Note
Fill Prefix::.
File: emacs, Node: Format Justification, Next: Format Properties, Prev: Format Indentation, Up: Formatted Text
Justification in Formatted Text
-------------------------------
When editing formatted text, you can specify various styles of
justification for a paragraph. The style you specify automatically
affects the Emacs fill commands.
The Justification submenu provides a convenient interface for
specifying the style. The submenu contains five items:
`Flush Left'
This is the most common style of justification (at least for
English). Lines are aligned at the left margin but left uneven at
the right.
`Flush Right'
This aligns each line with the right margin. Spaces and tabs are
added on the left, if necessary, to make lines line up on the
right.
`Full'
This justifies the text, aligning both edges of each line.
Justified text looks very nice in a printed book, where the spaces
can all be adjusted equally, but it does not look as nice with a
fixed-width font on the screen. Perhaps a future version of Emacs
will be able to adjust the width of spaces in a line to achieve
elegant justification.
`Center'
This centers every line between the current margins.
`None'
This turns off filling entirely. Each line will remain as you
wrote it; the fill and auto-fill functions will have no effect on
text which has this setting. You can, however, still indent the
left margin. In unfilled regions, all newlines are treated as
hard newlines (*note Hard and Soft Newlines::) .
In Enriched mode, you can also specify justification from the
keyboard using the `M-j' prefix character:
`M-j l'
Make the region left-filled (`set-justification-left').
`M-j r'
Make the region right-filled (`set-justification-right').
`M-j f'
Make the region fully-justified (`set-justification-full').
`M-j c'
`M-S'
Make the region centered (`set-justification-center').
`M-j u'
Make the region unfilled (`set-justification-none').
Justification styles apply to entire paragraphs. All the
justification-changing commands operate on the paragraph containing
point, or, if the region is active, on all paragraphs which overlap the
region.
The default justification style is specified by the variable
`default-justification'. Its value should be one of the symbols
`left', `right', `full', `center', or `none'.
File: emacs, Node: Format Properties, Next: Forcing Enriched Mode, Prev: Format Justification, Up: Formatted Text
Setting Other Text Properties
-----------------------------
The Other Properties menu lets you add or remove three other useful
text properties: `read-only', `invisible' and `intangible'. The
`intangible' property disallows moving point within the text, the
`invisible' text property hides text from display, and the `read-only'
property disallows alteration of the text.
Each of these special properties has a menu item to add it to the
region. The last menu item, `Remove Special', removes all of these
special properties from the text in the region.
Currently, the `invisible' and `intangible' properties are _not_
saved in the text/enriched format. The `read-only' property is saved,
but it is not a standard part of the text/enriched format, so other
editors may not respect it.
File: emacs, Node: Forcing Enriched Mode, Prev: Format Properties, Up: Formatted Text
Forcing Enriched Mode
---------------------
Normally, Emacs knows when you are editing formatted text because it
recognizes the special annotations used in the file that you visited.
However, there are situations in which you must take special actions to
convert file contents or turn on Enriched mode:
* When you visit a file that was created with some other editor,
Emacs may not recognize the file as being in the text/enriched
format. In this case, when you visit the file you will see the
formatting commands rather than the formatted text. Type `M-x
format-decode-buffer' to translate it.
* When you _insert_ a file into a buffer, rather than visiting it.
Emacs does the necessary conversions on the text which you insert,
but it does not enable Enriched mode. If you wish to do that,
type `M-x enriched-mode'.
The command `format-decode-buffer' translates text in various
formats into Emacs's internal format. It asks you to specify the format
to translate from; however, normally you can type just <RET>, which
tells Emacs to guess the format.
If you wish to look at text/enriched file in its raw form, as a
sequence of characters rather than as formatted text, use the `M-x
find-file-literally' command. This visits a file, like `find-file',
but does not do format conversion. It also inhibits character code
conversion (*note Coding Systems::) and automatic uncompression (*note
Compressed Files::). To disable format conversion but allow character
code conversion and/or automatic uncompression if appropriate, use
`format-find-file' with suitable arguments.
File: emacs, Node: Programs, Next: Building, 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 expressions--"defuns", in Lisp;
functions, in C (*note Defuns::).
* Show how parentheses balance (*note Matching::).
* Insert, kill or align comments (*note Comments::).
* Follow the usual indentation conventions of the language (*note
Program Indent::).
The commands for words, sentences and paragraphs are very 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 don't exist in code, but the paragraph commands are
useful anyway, because programming language major modes define
paragraphs to begin and end at blank lines (*note Paragraphs::).
Judicious use of blank lines to make the program clearer will also
provide useful 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.
* List Commands:: The commands for working with list and sexps.
* Defuns:: Each program is made up of separate functions.
There are editing commands to operate on them.
* Program Indent:: Adjusting indentation to show the nesting.
* Matching:: Insertion of a close-delimiter flashes matching open.
* Comments:: Inserting, killing, and aligning comments.
* Balanced Editing:: Inserting two matching parentheses at once, etc.
* Symbol Completion:: Completion on symbol names of your program or language.
* Which Function:: Which Function mode shows which function you are in.
* 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.
* Emerge:: A convenient way of merging two versions of a program.
* C Modes:: Special commands of C, C++, Objective-C,
Java, and Pike modes.
* Fortran:: Fortran mode and its special features.
* Asm Mode:: Asm mode and its special features.
File: emacs, Node: Program Modes, Next: Lists, Up: Programs
Major Modes for Programming Languages
=====================================
Emacs also has major modes for the programming languages Lisp, Scheme
(a variant of Lisp), Awk, C, C++, Fortran, Icon, Java, Objective-C,
Pascal, Perl, Pike, CORBA IDL, and Tcl. There is also a major mode for
makefiles, called Makefile mode. An second alternative mode for Perl is
called CPerl mode.
Ideally, a major mode should be implemented for each programming
language that 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 forms of Lisp mode, which differ in the way they
interface to Lisp execution. *Note Executing Lisp::.
Each of the programming language major 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'. `C-j' 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. Use `C-b C-d' to delete a tab character
before point, in these modes.
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 runs a normal hook called the "mode hook",
which is the value of a Lisp variable. Each major mode has a mode hook,
and the hook's name is always made from the mode command's name by
adding `-hook'. For example, turning on C mode runs the hook
`c-mode-hook', while turning on Lisp mode runs the hook
`lisp-mode-hook'. *Note Hooks::.
File: emacs, Node: Lists, Next: List Commands, 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 human languages).
These commands fall into two classes. Some deal only with "lists"
(parenthetical groupings). They see nothing except parentheses,
brackets, braces (whichever ones 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 ancient term for an expression in
Lisp. But in Emacs, the notion of `sexp' is not limited to Lisp. It
refers to an expression in whatever 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 a 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 single sexp in C
mode.
Some languages have obscure forms of expression syntax that nobody
has bothered to make Emacs understand properly.
File: emacs, Node: List Commands, Next: Defuns, Prev: Lists, Up: Programs
List And Sexp Commands
======================
`C-M-f'
Move forward over a sexp (`forward-sexp').
`C-M-b'
Move backward over a sexp (`backward-sexp').
`C-M-k'
Kill sexp forward (`kill-sexp').
`C-M-<DEL>'
Kill sexp backward (`backward-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 a 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.
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,
backquote and comma, in Lisp) preceding the sexp, `C-M-b' moves back
over them as well. The sexp commands move across comments as if they
were whitespace in most modes.
`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.
Killing a whole sexp can be done with `C-M-k' (`kill-sexp') or
`C-M-<DEL>' (`backward-kill-sexp'). `C-M-k' kills the characters that
`C-M-f' would move over, and `C-M-<DEL>' kills the characters that
`C-M-b' would move over.
The "list commands" move over lists, as the sexp commands do, but
skip blithely over any number of other kinds of sexps (symbols,
strings, etc.). They are `C-M-n' (`forward-list') and `C-M-p'
(`backward-list'). The main reason they are useful is that 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's 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.
A somewhat random-sounding command which is nevertheless handy is
`C-M-t' (`transpose-sexps'), which 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 set the region around the next sexp in the buffer, use `C-M-@'
(`mark-sexp'), which sets 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::.
File: emacs, Node: Defuns, Next: Program Indent, Prev: List Commands, 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 a Lisp file are instances of the special form `defun', but any
top-level parenthetical grouping counts as a defun in Emacs parlance
regardless of what its contents are, and regardless of the programming
language in use. 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').
If you wish to operate on the current defun, use `C-M-h'
(`mark-defun') which puts point at the beginning and mark at the end of
the current or next defun. For example, this is the easiest way to get
ready to move the defun to a different place in the text. In C mode,
`C-M-h' runs the function `c-mark-function', which is almost the same
as `mark-defun'; the difference is that it backs up over the argument
declarations, function name and returned data type so that the entire C
function is inside the region. *Note Marking Objects::.
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.
In the remotest past, the original Emacs found defuns by moving
upward a level of parentheses until there were no more levels to go up.
This always required scanning all the way back to the beginning of the
buffer, even for a small function. To speed up the operation, 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 and avoids the
costly scan; however, it mandates the convention described above.
File: emacs, Node: Program Indent, Next: Matching, Prev: Defuns, Up: Programs
Indentation for Programs
========================
The best way to keep a program properly indented is to use Emacs to
reindent it as you change it. 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:: Indenting a single line.
* Multi-line Indent:: Commands to reindent many lines at once.
* Lisp Indent:: Specifying how each Lisp function should be indented.
* C Indent:: Extra features for indenting C and related modes.
* Custom C Indent:: Controlling indentation style for C and related modes.
Emacs also provides a Lisp pretty-printer in the library `pp'. This
program reformats a Lisp object with indentation chosen to look nice.
File: emacs, Node: Basic Indent, Next: Multi-line Indent, Up: Program Indent
Basic Program Indentation Commands
----------------------------------
`<TAB>'
Adjust indentation of current line.
`C-j'
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 lines of new code, use `C-j' (`newline-and-indent'),
which is equivalent to a <RET> followed by a <TAB>. `C-j' creates a
blank line and 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 will
tend to follow it. This behavior is convenient in cases where you have
overridden the standard result of <TAB> because you find it unaesthetic
for a particular line.
Remember that an open-parenthesis, open-brace or other opening
delimiter at the left margin is assumed by Emacs (including the
indentation routines) to be the start of a function. Therefore, you
must 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; you must simply accept
it. *Note Defuns::, for more information on this.
File: emacs, Node: Multi-line Indent, Next: Lisp Indent, Prev: Basic Indent, Up: Program Indent
Indenting Several Lines
-----------------------
When you wish to reindent several lines of code which have been
altered or moved to a different level in the list structure, you have
several commands available.
`C-M-q'
Reindent 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-\'
Reindent all lines in the region (`indent-region').
You can reindent the contents of a single list by positioning point
before the beginning of it and typing `C-M-q' (`indent-sexp' in Lisp
mode, `c-indent-exp' in C mode; also bound to other suitable commands
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 the `C-M-q'.
If the relative indentation within a list is correct but the
indentation of its first line is not, go to that line and type `C-u
<TAB>'. <TAB> with a numeric argument reindents the current line as
usual, then reindents by the same amount all the lines in the grouping
starting on the current line. In other words, it reindents the whole
grouping rigidly as a unit. It is clever, though, and does not alter
lines that start inside strings, or C preprocessor lines when in C mode.
Another way to specify the range to be reindented is with the region.
The command `C-M-\' (`indent-region') applies <TAB> to every line whose
first character is between point and mark.
File: emacs, Node: Lisp Indent, Next: C Indent, Prev: Multi-line Indent, Up: Program Indent
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.
The standard pattern is overridden for certain functions. Functions
whose names start with `def' always indent the second line by
`lisp-body-indent' extra columns beyond the open-parenthesis starting
the expression.
The standard pattern can be overridden in various ways for individual
functions, according to the `lisp-indent-function' property of the
function name. 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 car 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 being 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.
File: emacs, Node: C Indent, Next: Custom C Indent, Prev: Lisp Indent, Up: Program Indent
Commands for C Indentation
--------------------------
Here are the commands for indentation in C mode and related modes:
`C-c C-q'
Reindent the current top-level function definition or aggregate
type declaration (`c-indent-defun').
`C-M-q'
Reindent each line in the balanced expression that follows point
(`c-indent-exp'). A prefix argument inhibits error checking and
warning messages about invalid syntax.
`<TAB>'
Reindent the current line, and/or in some cases insert a tab
character (`c-indent-command').
If `c-tab-always-indent' is `t', this command always reindents the
current line and does nothing else. This is the default.
If that variable is `nil', this command reindents the current line
only if point is at the left margin or in the line's indentation;
otherwise, it inserts a tab (or the equivalent number of spaces,
if `indent-tabs-mode' is `nil').
Any other value (not `nil' or `t') means always reindent the line,
and also insert a tab if within a comment, a string, or a
preprocessor directive.
`C-u <TAB>'
Reindent the current line according to its syntax; also rigidly
reindent any other lines of the expression that starts on the
current line. *Note Multi-line Indent::.
To reindent the whole current buffer, type `C-x h C-M-\'. This
first selects the whole buffer as the region, then reindents that
region.
To reindent the current block, use `C-M-u C-M-q'. This moves to the
front of the block and then reindents it all.
File: emacs, Node: Custom C Indent, Prev: C Indent, Up: Program Indent
Customizing C Indentation
-------------------------
C mode and related modes use a simple yet flexible mechanism for
customizing indentation. The mechanism works in two steps: first it
classifies the line syntactically according to its contents and context;
second, it associates each kind of syntactic construct with an
indentation offset which you can customize.
* Menu:
* Syntactic Analysis::
* Indentation Calculation::
* Changing Indent Style::
* Syntactic Symbols::
* Variables for C Indent::
* C Indent Styles::
File: emacs, Node: Syntactic Analysis, Next: Indentation Calculation, Up: Custom C Indent
Step 1--Syntactic Analysis
..........................
In the first step, the C indentation mechanism looks at the line
before the one you are currently indenting and determines the syntactic
components of the construct on that line. It builds a list of these
syntactic components, each of which contains a "syntactic symbol" and
sometimes also a buffer position. Some syntactic symbols describe
grammatical elements, for example `statement' and `substatement';
others describe locations amidst grammatical elements, for example
`class-open' and `knr-argdecl'.
Conceptually, a line of C code is always indented relative to the
indentation of some line higher up in the buffer. This is represented
by the buffer positions in the syntactic component list.
Here is an example. Suppose we have the following code in a C++ mode
buffer (the line numbers don't actually appear in the buffer):
1: void swap (int& a, int& b)
2: {
3: int tmp = a;
4: a = b;
5: b = tmp;
6: }
If you type `C-c C-s' (which runs the command
`c-show-syntactic-information') on line 4, it shows the result of the
indentation mechanism for that line:
((statement . 32))
This indicates that the line is a statement and it is indented
relative to buffer position 32, which happens to be the `i' in `int' on
line 3. If you move the cursor to line 3 and type `C-c C-s', it
displays this:
((defun-block-intro . 28))
This indicates that the `int' line is the first statement in a
block, and is indented relative to buffer position 28, which is the
brace just after the function header.
Here is another example:
1: int add (int val, int incr, int doit)
2: {
3: if (doit)
4: {
5: return (val + incr);
6: }
7: return (val);
8: }
Typing `C-c C-s' on line 4 displays this:
((substatement-open . 43))
This says that the brace _opens_ a substatement block. By the way,
a "substatement" indicates the line after an `if', `else', `while',
`do', `switch', `for', `try', `catch', `finally', or `synchronized'
statement.
Within the C indentation commands, after a line has been analyzed
syntactically for indentation, the variable `c-syntactic-context'
contains a list that describes the results. Each element in this list
is a "syntactic component": a cons cell containing a syntactic symbol
and (optionally) its corresponding buffer position. There may be
several elements in a component list; typically only one element has a
buffer position.
File: emacs, Node: Indentation Calculation, Next: Changing Indent Style, Prev: Syntactic Analysis, Up: Custom C Indent
Step 2--Indentation Calculation
...............................
The C indentation mechanism calculates the indentation for the
current line using the list of syntactic components,
`c-syntactic-context', derived from syntactic analysis. Each component
is a cons cell that contains a syntactic symbol and may also contain a
buffer position.
Each component contributes to the final total indentation of the line
in two ways. First, the syntactic symbol identifies an element of
`c-offsets-alist', which is an association list mapping syntactic
symbols into indentation offsets. Each syntactic symbol's offset adds
to the total indentation. Second, if the component includes a buffer
position, the column number of that position adds to the indentation.
All these offsets and column numbers, added together, give the total
indentation.
The following examples demonstrate the workings of the C indentation
mechanism:
1: void swap (int& a, int& b)
2: {
3: int tmp = a;
4: a = b;
5: b = tmp;
6: }
Suppose that point is on line 3 and you type <TAB> to reindent the
line. As explained above (*note Syntactic Analysis::), the syntactic
component list for that line is:
((defun-block-intro . 28))
In this case, the indentation calculation first looks up
`defun-block-intro' in the `c-offsets-alist' alist. Suppose that it
finds the integer 2; it adds this to the running total (initialized to
zero), yielding a updated total indentation of 2 spaces.
The next step is to find the column number of buffer position 28.
Since the brace at buffer position 28 is in column zero, this adds 0 to
the running total. Since this line has only one syntactic component,
the total indentation for the line is 2 spaces.
1: int add (int val, int incr, int doit)
2: {
3: if (doit)
4: {
5: return(val + incr);
6: }
7: return(val);
8: }
If you type <TAB> on line 4, the same process is performed, but with
different data. The syntactic component list for this line is:
((substatement-open . 43))
Here, the indentation calculation's first job is to look up the
symbol `substatement-open' in `c-offsets-alist'. Let's assume that the
offset for this symbol is 2. At this point the running total is 2 (0 +
2 = 2). Then it adds the column number of buffer position 43, which is
the `i' in `if' on line 3. This character is in column 2 on that line.
Adding this yields a total indentation of 4 spaces.
If a syntactic symbol in the analysis of a line does not appear in
`c-offsets-alist', it is ignored; if in addition the variable
`c-strict-syntax-p' is non-`nil', it is an error.
File: emacs, Node: Changing Indent Style, Next: Syntactic Symbols, Prev: Indentation Calculation, Up: Custom C Indent
Changing Indentation Style
..........................
There are two ways to customize the indentation style for the C-like
modes. First, you can select one of several predefined styles, each of
which specifies offsets for all the syntactic symbols. For more
flexibility, you can customize the handling of individual syntactic
symbols. *Note Syntactic Symbols::, for a list of all defined syntactic
symbols.
`M-x c-set-style <RET> STYLE <RET>'
Select predefined indentation style STYLE. Type `?' when entering
STYLE to see a list of supported styles; to find out what a style
looks like, select it and reindent some C code.
`C-c C-o SYMBOL <RET> OFFSET <RET>'
Set the indentation offset for syntactic symbol SYMBOL
(`c-set-offset'). The second argument OFFSET specifies the new
indentation offset.
The `c-offsets-alist' variable controls the amount of indentation to
give to each syntactic symbol. Its value is an association list, and
each element of the list has the form `(SYNTACTIC-SYMBOL . OFFSET)'.
By changing the offsets for various syntactic symbols, you can
customize indentation in fine detail. To change this alist, use
`c-set-offset' (see below).
Each offset value in `c-offsets-alist' can be an integer, a function
or variable name, a list, or one of the following symbols: `+', `-',
`++', `--', `*', or `/', indicating positive or negative multiples of
the variable `c-basic-offset'. Thus, if you want to change the levels
of indentation to be 3 spaces instead of 2 spaces, set `c-basic-offset'
to 3.
Using a function as the offset value provides the ultimate
flexibility in customizing indentation. The function is called with a
single argument containing the `cons' of the syntactic symbol and the
buffer position, if any. The function should return an integer offset.
If the offset value is a list, its elements are processed according
to the rules above until a non-`nil' value is found. That value is
then added to the total indentation in the normal manner. The primary
use for this is to combine the results of several functions.
The command `C-c C-o' (`c-set-offset') is the easiest way to set
offsets, both interactively or in your `~/.emacs' file. First specify
the syntactic symbol, then the offset you want. *Note Syntactic
Symbols::, for a list of valid syntactic symbols and their meanings.
File: emacs, Node: Syntactic Symbols, Next: Variables for C Indent, Prev: Changing Indent Style, Up: Custom C Indent
Syntactic Symbols
.................
Here is a table of valid syntactic symbols for indentation in C and
related modes, with their syntactic meanings. Normally, most of these
symbols are assigned offsets in `c-offsets-alist'.
`string'
Inside a multi-line string.
`c'
Inside a multi-line C style block comment.
`defun-open'
On a brace that opens a function definition.
`defun-close'
On a brace that closes a function definition.
`defun-block-intro'
In the first line in a top-level defun.
`class-open'
On a brace that opens a class definition.
`class-close'
On a brace that closes a class definition.
`inline-open'
On a brace that opens an in-class inline method.
`inline-close'
On a brace that closes an in-class inline method.
`extern-lang-open'
On a brace that opens an external language block.
`extern-lang-close'
On a brace that closes an external language block.
`func-decl-cont'
The region between a function definition's argument list and the
defun opening brace (excluding K&R function definitions). In C,
you cannot put anything but whitespace and comments between them;
in C++ and Java, `throws' declarations and other things can appear
in this context.
`knr-argdecl-intro'
On the first line of a K&R C argument declaration.
`knr-argdecl'
In one of the subsequent lines in a K&R C argument declaration.
`topmost-intro'
On the first line in a topmost construct definition.
`topmost-intro-cont'
On the topmost definition continuation lines.
`member-init-intro'
On the first line in a member initialization list.
`member-init-cont'
On one of the subsequent member initialization list lines.
`inher-intro'
On the first line of a multiple inheritance list.
`inher-cont'
On one of the subsequent multiple inheritance lines.
`block-open'
On a statement block open brace.
`block-close'
On a statement block close brace.
`brace-list-open'
On the opening brace of an `enum' or `static' array list.
`brace-list-close'
On the closing brace of an `enum' or `static' array list.
`brace-list-intro'
On the first line in an `enum' or `static' array list.
`brace-list-entry'
On one of the subsequent lines in an `enum' or `static' array list.
`brace-entry-open'
On one of the subsequent lines in an `enum' or `static' array
list, when the line begins with an open brace.
`statement'
On an ordinary statement.
`statement-cont'
On a continuation line of a statement.
`statement-block-intro'
On the first line in a new statement block.
`statement-case-intro'
On the first line in a `case' "block."
`statement-case-open'
On the first line in a `case' block starting with brace.
`inexpr-statement'
On a statement block inside an expression. This is used for a GNU
extension to the C language, and for Pike special functions that
take a statement block as an argument.
`inexpr-class'
On a class definition inside an expression. This is used for
anonymous classes and anonymous array initializers in Java.
`substatement'
On the first line after an `if', `while', `for', `do', or `else'.
`substatement-open'
On the brace that opens a substatement block.
`case-label'
On a `case' or `default' label.
`access-label'
On a C++ `private', `protected', or `public' access label.
`label'
On any ordinary label.
`do-while-closure'
On the `while' that ends a `do'-`while' construct.
`else-clause'
On the `else' of an `if'-`else' construct.
`catch-clause'
On the `catch' and `finally' lines in `try'...`catch' constructs
in C++ and Java.
`comment-intro'
On a line containing only a comment introduction.
`arglist-intro'
On the first line in an argument list.
`arglist-cont'
On one of the subsequent argument list lines when no arguments
follow on the same line as the arglist opening parenthesis.
`arglist-cont-nonempty'
On one of the subsequent argument list lines when at least one
argument follows on the same line as the arglist opening
parenthesis.
`arglist-close'
On the closing parenthesis of an argument list.
`stream-op'
On one of the lines continuing a stream operator construct.
`inclass'
On a construct that is nested inside a class definition. The
indentation is relative to the open brace of the class definition.
`inextern-lang'
On a construct that is nested inside an external language block.
`inexpr-statement'
On the first line of statement block inside an expression. This
is used for the GCC extension to C that uses the syntax `({ ...
})'. It is also used for the special functions that takes a
statement block as an argument in Pike.
`inexpr-class'
On the first line of a class definition inside an expression.
This is used for anonymous classes and anonymous array
initializers in Java.
`cpp-macro'
On the start of a cpp macro.
`friend'
On a C++ `friend' declaration.
`objc-method-intro'
On the first line of an Objective-C method definition.
`objc-method-args-cont'
On one of the lines continuing an Objective-C method definition.
`objc-method-call-cont'
On one of the lines continuing an Objective-C method call.
`inlambda'
Like `inclass', but used inside lambda (i.e. anonymous) functions.
Only used in Pike.
`lambda-intro-cont'
On a line continuing the header of a lambda function, between the
`lambda' keyword and the function body. Only used in Pike.