OS/2 Professional/OS2PRO194.ISO/os2/prgramer/unix/info/emacs.i07

GNU Info File | 1993-06-14 | 50.1 KB | 1,164 lines

This is Info file ../info/emacs, produced by Makeinfo-1.47 from the
input file emacs.tex.

   This file documents the GNU Emacs editor.

   Copyright (C) 1985, 1986, 1988 Richard M. Stallman.

   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.


File: emacs,  Node: Paragraphs,  Next: Pages,  Prev: Sentences,  Up: Text

Paragraphs
==========

   The Emacs commands for manipulating paragraphs are also `Meta-' keys.

`M-['
     Move back to previous paragraph beginning
     (`backward-paragraph').

`M-]'
     Move forward to next paragraph end (`forward-paragraph').

`M-h'
     Put point and mark around this or next paragraph
     (`mark-paragraph').

   `Meta-[' moves to the beginning of the current or previous paragraph,
while `Meta-]' moves to the end of the current or next paragraph. Blank
lines and text formatter command lines separate paragraphs and are not
part of any paragraph.  Also, an indented line starts a new paragraph.

   In major modes for programs (as opposed to Text mode), paragraphs
begin and end only at blank lines.  This makes the paragraph commands
continue to be useful even though there are no paragraphs per se.

   When there is a fill prefix, then paragraphs are delimited by all
lines which don't start with the fill prefix.  *Note Filling::.

   When you wish to operate on a paragraph, you can use the command
`Meta-h' (`mark-paragraph') to set the region around it.  This command
puts point at the beginning and mark at the end of the paragraph point
was in.  If point is between paragraphs (in a run of blank lines, or at
a boundary), the paragraph following point is surrounded by point and
mark.  If there are blank lines preceding the first line of the
paragraph, one of these blank lines is included in the region.  Thus,
for example, `M-h C-w' kills the paragraph around or after point.

   The precise definition of a paragraph boundary is controlled by the
variables `paragraph-separate' and `paragraph-start'.  The value of
`paragraph-start' is a regexp that should match any line that either
starts or separates paragraphs.  The value of `paragraph-separate' is
another regexp that should match only lines that separate paragraphs
without being part of any paragraph.  Lines that start a new paragraph
and are contained in it must match both regexps.  For example, normally
`paragraph-start' is `"^[ \t\n\f]"' and `paragraph-separate' is `"^[
\t\f]*$"'.

   Normally it is desirable for page boundaries to separate paragraphs.
The default values of these variables recognize the usual separator for
pages.


File: emacs,  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, in this sense, will
start 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.  Thus, 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, it 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).  This command can be followed by `C-w' to
kill a page which is to be moved elsewhere.  If it is inserted after a
page delimiter, at a place where `C-x ]' or `C-x [' would take you, then
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') is good for deciding where
to break a page in two.  It prints in the echo area the total number of
lines in the current page, and then divides it up into those preceding
the current line and those following, as in

     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 is what
defines where pages begin.  The normal value of this variable is
`"^\f"', which matches a formfeed character at the beginning of a line.


File: emacs,  Node: Filling,  Next: Case,  Prev: Pages,  Up: Text

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

   With Auto Fill mode, text can be "filled" (broken up into lines that
fit in a specified width) as you insert it.  If you alter existing text
it may no longer be properly filled; then explicit commands for filling
can be used.

* 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.


File: emacs,  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 it always turns Auto Fill
mode on, and with a negative argument always turns it off.  You can see
when Auto Fill mode is in effect by the presence of the word `Fill' in
the mode line, inside the parentheses.  Auto Fill mode is a minor mode,
turned 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 the desired width.  Line breaking and
rearrangement takes place only when you type SPC or RET.  If you wish
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).
Also, `C-o' inserts a newline without line breaking.

   Auto Fill mode works well with Lisp mode, because when it makes a new
line in Lisp mode it indents that line with TAB.  If a line ending in a
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.  So 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 usually with the
explicit fill commands.

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


File: emacs,  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 that point is inside, or the one after point if
point is between paragraphs, to be refilled.  All the line-breaks are
removed, and then 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.  This means that 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 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 that time, the default value is in effect.  The default is
initially 70.  *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 as the new fill column.


File: emacs,  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 Emacs expects
every line to start with, and which is not included in filling.

`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. The fill prefix is also inserted on new lines made
automatically by Auto Fill mode.  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.


File: emacs,  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 the most useful.  `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.  All these 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,
because 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.


File: emacs,  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 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 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 will also provide 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.


File: emacs,  Node: Program Modes,  Next: Lists,  Prev: Programs,  Up: Programs

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

   Emacs also has 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 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 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.  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 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.


File: emacs,  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).

   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 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 a sexp (`forward-sexp').

`C-M-b'
     Move backward over a 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 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.  If the character after point is a closing
delimiter, `C-M-f' just moves past it.  (This last is not really moving
across a 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 (singlequote,
backquote 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.

   The sexp commands move across comments as if they were whitespace, in
languages such as C where the comment-terminator can be recognized.  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 a 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" move over lists like the sexp commands 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 easy to use
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 make the region be 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: 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 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 `mark-c-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.

   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 was nearly always right and avoided the
costly scan; however, it mandated the convention described above.


File: emacs,  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 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::
* 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.


File: emacs,  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, and then gives it the appropriate
indentation.

   TAB indents the second and following lines of the body of an
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 is the right behavior in cases where the
standard result of TAB is unaesthetic.

   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: Grinding

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

   When you wish to re-indent 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'
     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').

   You can re-indent the contents of a single list by positioning point
before the beginning of it and typing `C-M-q' (`indent-sexp' in Lisp
mode, `indent-c-exp' in C mode; also 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 the `C-M-q'.

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

   Another way to specify the 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.


File: emacs,  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.

   The standard pattern is overridded for certain functions.  Functions
whose names start with `def' always indent the second line by
`lisp-body-indention' 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-hook' 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,  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,
then 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 line if it starts 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 line that is a label, or 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.  I prefer 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 nonblank character on the line.
By setting this 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
will line up right under the open brace.  But there is an exception made
for braces in column zero, such as surrounding a function's body.  The
statements just inside it do not go 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 that are within other
statements, such as the then-clauses of `if' statements and the bodies
of `while' statements.  This parameter is the difference in indentation
between the two lines in

     if (x == y)
       do_it ();

Its standard value 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 `c-brace-offset' were set to 4, the first example would become

     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,
resulting 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, resulting 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
standard values.

   I strongly recommend that you try out the indentation style produced
by the standard settings of these variables, together with putting open
braces on separate lines.  You can see how it looks in all the C source
files of GNU Emacs.


File: emacs,  Node: Matching,  Next: Comments,  Prev: Grinding,  Up: Programs

Automatic Display Of Matching Parentheses
=========================================

   The Emacs parenthesis-matching feature is designed to show
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 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 can tell what grouping is being closed off.

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

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

   Two variables control parenthesis match display.
`blink-matching-paren' turns the feature on or off; `nil' turns it off,
but the default is `t' to turn match display on.
`blink-matching-paren-distance' specifies how many characters back to
search to find the matching opening delimiter.  If the match is not
found in that far, scanning stops, and nothing is displayed.  This is
to prevent scanning for the matching delimiter from wasting lots of
time when there is no match.  The default is 4000.


File: emacs,  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, aligned at a specific column called the
"comment column".  The comment is created by inserting the string Emacs
thinks comments should start with (the value of `comment-start'; see
below).  Point is left after that string.  If the text of the line
extends past the comment column, then the 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 is
inserted after point, to keep the syntax valid.

   `Meta-;' can also be used to align an existing comment.  If a line
already contains the string that starts comments, then `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 is done.  To reinsert the comment on another line, move to the
end of that line, do `C-y', and then do `M-;' to realign it.  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 so that when it receives a negative argument it calls
`kill-comment'.  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 find that you wish to continue it on
another line, you can 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.  When Auto Fill mode is on, going past the
fill column while typing a comment causes the comment to be continued
in just this fashion.  If point is not at the end of the line when
`M-LFD' is typed, 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 set it to a number explicitly.  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 does a `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, but there is a default value which you
can change as well.  *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, so that it will follow the text that 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 the comment on the starting line is terminated
and a new comment is started on the new following line.  If
`comment-multi-line' is not `nil', then the new following line is set
up 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 work, the choice of value for this variable is a matter of
taste.

   The variable `comment-indent-hook' should contain a function that
will be called to compute the indentation for a newly inserted comment
or for aligning an existing comment.  It is set differently by various
major modes.  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.  It should return the column in which the
comment ought to start. For example, in Lisp mode, the indent hook
function bases its decision on how many semicolons begin an existing
comment, and on the code in the preceding lines.


File: emacs,  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.  Then you would type `M-)', which moves past the
close parenthesis, deleting any indentation preceding it (in this
example there is none), and indenting with LFD after it.