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Info file elisp, produced by Makeinfo, -*- Text -*- from input file
elisp.texi.
This file documents GNU Emacs Lisp.
This is edition 1.03 of the GNU Emacs Lisp Reference Manual, for
Emacs Version 18.
Published by the Free Software Foundation, 675 Massachusetts
Avenue, Cambridge, MA 02139 USA
Copyright (C) 1990 Free Software Foundation, Inc.
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 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 this permission notice may be stated in a
translation approved by the Foundation.
File: elisp, Node: Commands for Insertion, Next: Deletion, Prev: Insertion, Up: Text
User-Level Insertion Commands
=============================
This section describes higher-level commands for inserting text,
commands intended primarily for the user but useful also in Lisp
programs.
* Command: insert-buffer FROM-BUFFER-OR-NAME
This function inserts the entire contents of FROM-BUFFER-OR-NAME
(which must exist) into the current buffer after point. It
leaves the mark after the inserted text. The value is
unpredictable.
* Command: quoted-insert COUNT
This function reads the next input character verbatim and
inserts it. It is primarily useful for inserting control
characters. You may also type up to 3 octal digits, to insert a
character with that code.
The argument COUNT is the number of these characters to insert.
An error is signaled if COUNT is not a number.
This function is primarily for interactive use; there is no
reason to use it in a program except for installing it on a
keymap. It returns `nil'.
* Command: self-insert-command COUNT
This function inserts the last character typed COUNT times and
returns `nil'. This is the function that most printing
characters are bound to. In routine use, `self-insert-command'
is the most frequently called function in Emacs, but programs
rarely use it except to install it on a keymap.
In an interactive call, COUNT is the numeric prefix argument.
This function calls `auto-fill-hook' if the current column
number is greater than the value of `fill-column' and the
character inserted is a space (*note Auto Filling::.).
This function performs abbrev expansion if Abbrev mode (*note
Abbrevs::.) is enabled and the inserted character does not have
word-constituent syntax (*note Syntax Class Table::.).
This function is also responsible for calling the
`blink-paren-hook' when the inserted character has close
parenthesis syntax (*note Blinking::.).
* Command: newline &optional NUMBER-OF-NEWLINES
This function inserts newlines into the current buffer before
point. If NUMBER-OF-NEWLINES is supplied, that many newline
characters are inserted.
In Auto Fill mode, `newline' can break the preceding line if
NUMBER-OF-NEWLINES is not supplied. When this happens, it
actually inserts two newlines at different places: one at point,
and another earlier in the line. `newline' does not auto-fill
if NUMBER-OF-NEWLINES is non-`nil'.
The value returned is `nil'. In an interactive call, COUNT is
the numeric prefix argument.
* Command: split-line
This function splits the current line, moving the portion of the
line after point down vertically, so that it is on the next line
directly below where it was before. Whitespace is inserted as
needed at the beginning of the lower line, using the `indent-to'
function. `split-line' returns the position of point.
Programs hardly ever use this function.
* Command: open-line COUNT
This function inserts COUNT newlines into the current buffer
after point, leaving point where it was.
In an interactive call, COUNT is the numeric prefix argument.
Programs hardly ever use this function. The value is
unpredictable.
* Command: overwrite-mode ARGUMENT
This function turns Overwrite mode on or off. If ARGUMENT is
`nil' then the mode is toggled. Otherwise, if ARGUMENT is a
positive number (greater than zero), then the mode is turned on;
any other argument turns it off.
When Overwrite mode is on, self-inserting graphic characters
replace existing text character for character, and do not push
the existing text to the right.
This function affects primarily `self-insert-command'.
In an interactive call, ARGUMENT is set to the raw prefix
argument. The return value of `overwrite-mode' is unpredictable.
* Variable: overwrite-mode
Overwrite mode is in effect when this variable is non-`nil'. It
is automatically made buffer-local when set in any fashion.
File: elisp, Node: Deletion, Next: User-Level Deletion, Prev: Commands for Insertion, Up: Text
Deletion of Text
================
All of the deletion functions operate on the current buffer, and
all return a value of `nil'. In addition to these functions, you can
also delete text using the "kill" functions that save it in the kill
ring for the user; some of these functions save text in the kill ring
in some cases but not in the usual case. *Note The Kill Ring::.
* Function: erase-buffer
This function deletes the entire text of the current buffer,
leaving it empty. If the buffer is read-only, it signals a
`buffer-read-only' error. Otherwise the text is deleted with no
confirmation required. The value is always `nil'.
As a safety measure, this function is not interactively callable.
* Command: delete-region START END
This function deletes the text in the current buffer in the
region defined by START and END. The value is `nil'.
* Command: delete-char COUNT &optional KILLP
This function deletes COUNT characters directly after point, or
before point if COUNT is negative. If KILLP is non-`nil', then
it saves the deleted characters in the kill ring.
In an interactive call, COUNT is the numeric prefix argument,
and KILLP is the unprocessed prefix argument. Therefore, if a
prefix argument is supplied, the text is saved in the kill ring.
If no prefix argument is supplied, then one character is
deleted, but not saved in the kill ring.
The value returned is always `nil'.
* Command: delete-backward-char COUNT &optional KILLP
This function deletes COUNT characters directly before point, or
after point if COUNT is negative. If KILLP is non-`nil', then
it saves the deleted characters in the kill ring.
In an interactive call, COUNT is the numeric prefix argument,
and KILLP is the unprocessed prefix argument. Therefore, if a
prefix argument is supplied, the text is saved in the kill ring.
If no prefix argument is supplied, then one character is
deleted, but not saved in the kill ring.
The value returned is always `nil'.
* Command: backward-delete-char-untabify COUNT &optional KILLP
This function deletes COUNT characters backward, changing tabs
into spaces. When the next character to be deleted is a tab, it
is first replaced with the proper number of spaces to preserve
alignment and then one of those spaces is deleted instead of the
tab. If KILLP is non-`nil', then the command saves the deleted
characters in the kill ring.
If COUNT is negative, then tabs are not changed to spaces, and
the characters are deleted by calling `delete-backward-char'
with COUNT.
In an interactive call, COUNT is the numeric prefix argument,
and KILLP is the unprocessed prefix argument. Therefore, if a
prefix argument is supplied, the text is saved in the kill ring.
If no prefix argument is supplied, then one character is
deleted, but not saved in the kill ring.
The value returned is always `nil'.
File: elisp, Node: User-Level Deletion, Next: The Kill Ring, Prev: Deletion, Up: Text
User-Level Deletion Commands
============================
This section describes higher-level commands for deleting text,
commands intended primarily for the user but useful also in Lisp
programs.
* Command: delete-horizontal-space
This function deletes all spaces and tabs around point. It
returns `nil'.
In the following examples, assume that `delete-horizontal-space'
is called four times, once on each line, with point between the
second and third characters on the line.
---------- Buffer: foo ----------
I -!-thought
I -!- thought
We-!- thought
Yo-!-u thought
---------- Buffer: foo ----------
(delete-horizontal-space) ; Four times.
=> nil
---------- Buffer: foo ----------
Ithought
Ithought
Wethought
You thought
---------- Buffer: foo ----------
* Command: delete-indentation &optional JOIN-FOLLOWING-P
This function joins the line point is on to the previous line,
deleting any whitespace at the join and in some cases replacing
it with one space. If JOIN-FOLLOWING-P is non-`nil',
`delete-indentation' joins this line to following line instead.
The value is `nil'.
In the example below, point is located on the line starting
`events', and it makes no difference if there are trailing
spaces in the preceding line.
---------- Buffer: foo ----------
When in the course of human
-!- events, it becomes necessary
---------- Buffer: foo ----------
(delete-indentation)
=> nil
---------- Buffer: foo ----------
When in the course of human-!- events, it becomes necessary
---------- Buffer: foo ----------
After the lines are joined, the function `fixup-whitespace' is
responsible for deciding whether to leave a space at the junction.
* Function: fixup-whitespace
This function replaces white space between the objects on either
side of point with either one space or no space as appropriate.
It returns `nil'.
The appropriate amount of space is none at the beginning or end
of the line. Otherwise, it is one space except when point is
before a character with close parenthesis syntax or after a
character with open parenthesis or expression-prefix syntax.
*Note Syntax Class Table::.
In the example below, point is at the beginning of the second
line when `fixup-whitespace' is called the first time. It is
located directly after the `(' for the second invocation.
---------- Buffer: foo ----------
This has too many spaces
-!- at the front of this line
This has too many spaces at the start of (-!- this list)
---------- Buffer: foo ----------
(fixup-whitespace)
=> nil
(fixup-whitespace)
=> nil
---------- Buffer: foo ----------
This has too many spaces
at the front of this line
This has too many spaces at the start of (this list)
---------- Buffer: foo ----------
* Command: just-one-space
This command replaces any spaces and tabs around point with a
single space. It returns `nil'.
* Command: delete-blank-lines
This function deletes blank lines surrounding point. If point
is on a blank line with one or more blank lines before or after
it, then all but one of them are deleted. If point is on an
isolated blank line, then it is deleted. If point is on a
nonblank line, the command deletes all blank lines following it.
A blank line is defined as a line containing only tabs and spaces.
`delete-blank-lines' returns `nil'.
File: elisp, Node: The Kill Ring, Next: Undo, Prev: User-Level Deletion, Up: Text
The Kill Ring
=============
"Kill" functions delete text like the deletion functions, but save
it so that the user can reinsert it by "yanking". Most of these
functions have `kill-' in their name. By contrast, the functions
whose names start with `delete-' normally do not save text for
yanking (though they can still be undone); these are "deletion"
functions.
Most of the kill commands are primarily for interactive use, and
are not described here. What we do describe are the functions
provided for use in writing such commands. When deleting text for
internal purposes within a Lisp function, you should normally use
deletion functions, so as not to disturb the kill ring contents.
*Note Deletion::.
Emacs saves the last several batches of killed text in a list. We
call it the "kill ring" because, in yanking, the elements are
considered to be in a cyclic order. The list is kept in the variable
`kill-ring', and can be operated on with the usual functions for
lists; there are also specialized functions, described in this
section, which treat it as a ring.
Some people think use of the word "kill" in Emacs is unfortunate,
since it refers to processes which specifically *do not* destroy the
entities "killed". This is in sharp contrast to ordinary life, in
which death is permanent and "killed" entities do not come back to
life. Therefore, other metaphors have been proposed. For example,
the term "cut ring" makes sense to people who, in pre-computer days,
used scissors and paste to cut up and rearrange manuscripts.
However, it would be difficult to change now.
* Menu:
* Data in Kill Ring:: What text looks like in the kill ring.
* Kill Functions:: Functions that kill text.
* Yank Commands:: Commands that access the kill ring.
* Kill Ring Internals:: Variables that hold kill-ring data.
File: elisp, Node: Data in Kill Ring, Next: Kill Functions, Prev: The Kill Ring, Up: The Kill Ring
Data Structures in the Kill Ring
--------------------------------
Killed text is kept as strings in a list. A short kill ring, for
example, might look like this:
("some text" "a different piece of text" "yet more text")
Functions that push more text into the list make the text in
question into a string (using `buffer-substring'), add the string to
the front of the list, and then look at the length of the list. If
the length is longer than the value of `kill-ring-max', the last
entry in the list is dropped off when the new entry is put on.
The `kill-ring-yank-pointer' global variable points to the kill
ring entry that a "yank" function will copy. Several functions move
this pointer from one entry to another, and a user can thereby
specify which entry to copy.
Here is a diagram that shows the variable `kill-ring-yank-pointer'
pointing to the second entry in the kill ring `("some text" "a
different piece of text" "yet more text")'.
kill-ring kill-ring-yank-pointer
| |
| ___ ___ ---> ___ ___ ___ ___
--> |___|___|------> |___|___|--> |___|___|--> nil
| | |
| | |
| | -->"yet more text"
| |
| --> "a different piece of text"
|
--> "some text"
(This circumstance occurs after `C-y' (`yank') is immediately
followed by `M-y' (`yank-pop').)
Both `kill-ring' and `kill-ring-yank-pointer' are Lisp variables
whose values are normally lists. The word "pointer" in the name of
the `kill-ring-yank-pointer' indicates that the variable's purpose is
to identify one element of the list that will be used by default by
the next yank command. The value of `kill-ring-yank-pointer' is
always `eq' to one of the links in the kill ring list. The element
it identifies is the CAR of that link.
Moving `kill-ring-yank-pointer' to a different link is called
"rotating the kill ring". The functions that do this treat the kill
ring (which is a list) as ring; that is to say, a change that would
otherwise move the pointer past the end of the list (which would be
useless) instead moves the pointer to the first link on the list.
Likewise, moving back from the first link goes to the last one.
`kill-region' is the primitive method of killing text. Any
command that calls this function is a "kill command" (and should
probably have the word "kill" in its name). `kill-region' puts the
newly killed text in a new element at the beginning of the
`kill-ring' list, and then sets `kill-ring-yank-pointer' to point to
the first link of the list, which contains the first element.
Consequently, the next `yank' command will yank the text just killed.
In this situation, `kill-ring' and `kill-ring-yank-pointer' are `eq'
to each other.
When kill commands are interwoven with other commands, the killed
portions of text are put into separate entries in the kill ring. But
when two or more kill commands are executed in sequence, the text
killed by the second (or third, etc.) kill command is appended to the
text killed by the first command so as to make one entry in the kill
ring. The `kill-region' function uses the `last-command' variable to
keep track of whether the previous was a kill command, and in such
cases appends the killed text to the most recent entry.
File: elisp, Node: Kill Functions, Next: Yank Commands, Prev: Data in Kill Ring, Up: The Kill Ring
Functions for Killing
---------------------
* Command: kill-region START END
This function kills the text in the region defined by START and
END. The text is deleted but saved in the kill ring. The value
is always `nil'.
In an interactive call, START and END are point and the mark.
* Command: kill-line &optional COUNT
This function kills the rest of the line following point, not
including the newline. If point is directly before a newline,
or if there is only whitespace between point and the newline,
then it kills the whitespace and newline.
If COUNT is supplied, then the command kills that many lines
(*including* the newline). (This makes executing `(kill-line
2)' different from executing `(kill-line)' twice.) If COUNT is
negative, then `kill-line' kills lines backwards.
In an interactive call, COUNT is the raw prefix argument (which
then gets converted to a number if non-`nil'). The value is
always `nil'.
* Command: zap-to-char COUNT CHARACTER
In Emacs version 18, this function kills the text from point up
to *but not including* the specified character. Thus, if the
cursor is at the beginning of this sentence and the character is
`s', `Thu' is deleted. If the argument is 2, `Thus, if the cur'
is deleted, up to but not including the `s' in `cursor'.
In Emacs version 19, this function will kill all text in the
region from point up to and including the next COUNT occurrences
of CHARACTER. Thus, in the example shown in the previous
paragraph, the terminating `s' *will* be removed.
The version 18 implementation kills text to the end of the
buffer if the specified character is not found, but the version
19 implementation will simply signal an error.
The function scans backward from point if COUNT is negative.
The value is always `nil'.
* Command: copy-region-as-kill START END
This function saves the region defined by START and END on the
kill ring, but does not delete the text from the buffer. It
returns `nil'.
In an interactive call, START and END are point and the mark.
File: elisp, Node: Yank Commands, Next: Kill Ring Internals, Prev: Kill Functions, Up: The Kill Ring
Functions for Yanking
---------------------
* Command: yank &optional ARG
This function inserts the text in the first entry in the kill
ring directly before point. After the yank, the mark is
positioned at the beginning and point is positioned after the
end of the inserted text.
If ARG is a list (which occurs interactively when the user types
`C-u' with no digits), then `yank' inserts the text as described
above, but puts point before the yanked text and puts the mark
after it. If ARG is a number, then `yank' inserts the ARGth
most recently killed text.
`yank' does not alter the contents of the kill ring or rotate it.
It returns `nil'.
* Command: yank-pop ARG
This function replaces the just-yanked text with another batch
of killed text--another element of the kill ring.
This command is allowed only immediately after a `yank' or a
`yank-pop'. At such a time, the region contains text that was
just inserted by the previous `yank'. `yank-pop' deletes that
text and inserts in its place a different stretch of killed
text. The text that is deleted is not inserted into the kill
ring, since it is already in the kill ring somewhere.
If ARG is `nil', then the existing region contents are replaced
with the previous element of the kill ring. If ARG is numeric,
then the ARG'TH previous kill is the replacement. If ARG is
negative, a more recent kill is the replacement.
The sequence of kills in the kill ring wraps around, so that
after the oldest one comes the newest one, and before the newest
one goes the oldest.
The value is always `nil'.
File: elisp, Node: Kill Ring Internals, Prev: Yank Commands, Up: The Kill Ring
Internals of the Kill Ring
--------------------------
This section describes the lower levels of the kill ring.
* Variable: kill-ring
List of killed text sequences, most recently killed first.
* Variable: kill-ring-yank-pointer
This variable's value indicates which element of the kill ring
is the "front" of the ring. More precisely, the value is a
sublist of the value of `kill-ring', and its CAR is the kill
string at the front of the ring. Rotating the ring works by
changing `kill-ring-yank-pointer', and does not actually change
the value of `kill-ring'.
Commands which do change the kill ring also copy the new kill
ring value into this variable. The effect is to rotate the ring
so that the newly killed text is at front.
* Command: rotate-yank-pointer COUNT
This function rotates the kill ring COUNT positions, which means
setting `kill-ring-yank-pointer' to some other link in the kill
ring list. It returns the new value of `kill-ring-yank-pointer'.
* User Option: kill-ring-max
The value of this variable is the maximum length to which the
kill ring can grow, before elements are thrown away on a
first-in, first-out basis. The default value for
`kill-ring-max' is 30.
File: elisp, Node: Undo, Next: Filling, Prev: The Kill Ring, Up: Text
Undo
====
Most buffers have an "undo stack" which records all changes made
to the buffer's text so that they can be undone. (In general, all
buffers have undo stacks except special-purpose buffers for which
Emacs assumes that undoing is not useful.) The size of an undo stack
is limited, so large changes or a large number of changes cannot be
undone.
Undoing an old change is itself a change, and is added to the undo
stack. However, you are not limited to undoing just the single most
recent change; you can keep undoing older and older changes, even as
the undo's themselves are being added to the stack.
* Command: undo &optional ARG
This is a user-level command to undo some previous changes. It
uses `undo-more' and `undo-start'. By repeating this command
you can undo earlier and earlier changes, until the information
in the undo stack is used up. A numeric argument serves as a
repeat count. The value is unpredictable.
* Function: undo-boundary
This function places a boundary between units of undo. The undo
command stops at such a boundary, and successive undo commands
will undo to earlier and earlier boundaries. The return value
is `nil'.
The editor command loop automatically creates an undo boundary
between keystroke commands. Thus, each undo normally undoes the
effects of one command. Calling this function explicitly is
useful for splitting the effects of a command into more than one
unit. For example, `query-replace' calls this function after
each replacement so that the user can undo individual
replacements one by one.
* Function: undo-more COUNT
This function is used to undo COUNT additional units of undo.
It is not safe if the buffer has been changed in any fashion
other than undo since the last call to `undo-start'. Multiple
calls to `undo-more' have a cumulative effect, undoing farther
back in time. The return value is `nil'.
* Function: undo-start
This function prepares to undo one or more units of undo
describing the most recent changes to the current buffer. It
does not actually undo anything (or change the buffer at all);
only `undo-more' does that. It returns `nil'.
One use of this function is to break a sequence of undo's, so a
subsequent call to `undo-more' will undo the recent run of
undoing, rather than extend it into the past.
The command `undo' calls `undo-start' whenever the previous
command was not an `undo'.
* Command: buffer-enable-undo &optional BUFFER-OR-NAME
This function assigns an undo stack for buffer BUFFER-OR-NAME,
so that subsequent changes can be undone. If no argument is
supplied, then the current buffer is used. If the buffer
already has an undo stack, nothing is changed. This function
returns `nil'.
In an interactive call, BUFFER-OR-NAME is the current buffer.
You cannot specify any other buffer.
* Function: buffer-flush-undo BUFFER
This function deassigns the undo stack of the buffer BUFFER, so
that it will not take up space. As a result, it is no longer
possible to undo either previous changes or any subsequent
changes. If the buffer already has no undo stack, then this
function has no effect.
This function returns `nil'. It cannot be called interactively.
File: elisp, Node: Filling, Next: Auto Filling, Prev: Undo, Up: Text
Filling
=======
"Filling" means adjusting the lengths of lines (by moving words
between them) so that they are nearly (but no greater than) a
specified maximum width. Additionally, lines can be "justified",
which means that spaces are inserted between words to make the line
exactly the specified width. The width is controlled by the variable
`fill-column'. For ease of reading, lines should be no longer than
70 or so columns.
You can use Auto Fill mode (*note Auto Filling::.) to fill text
automatically as you insert it, but changes to existing text may
leave it improperly filled. Then you must fill the text explicitly.
Most of the functions in this section return values that are not
meaningful.
* Command: fill-paragraph JUSTIFY-FLAG
This function fills the paragraph at or after point. If
JUSTIFY-FLAG is non-`nil', each line is justified as well.
* Command: fill-region START END &optional JUSTIFY-FLAG
This function fills each of the paragraphs in the region from
start to end. It justifies as well if JUSTIFY-FLAG is
non-`nil'. (In an interactive call, this is true if there is a
prefix argument.)
The variable `paragraph-separate' controls how to distinguish
paragraphs.
* Command: fill-individual-paragraphs START END &optional
JUSTIFY-FLAG MAIL-FLAG
This function fills each paragraph in the region according to
its individual fill prefix. Thus, if the lines of a paragraph
are indented with spaces, the filled paragraph will continue to
be indented in the same fashion.
The first two arguments, START and END, are the beginning and
end of the region that will be filled. The third and fourth
arguments, JUSTIFY-FLAG and MAIL-FLAG, are optional. If
JUSTIFY-FLAG is non-`nil', the paragraphs are justified as well
as filled. If MAIL-FLAG is non-`nil', the function is told that
it is operating on a mail message and therefore should not fill
the header lines.
* Command: fill-region-as-paragraph START END &optional JUSTIFY-FLAG
This function considers a region of text as a paragraph and
fills it. If the region was made up of many paragraphs, the
blank lines between paragraphs are removed. This function
justifies as well as filling when JUSTIFY-FLAG is non-`nil'. In
an interactive call, any prefix argument requests justification.
* Command: justify-current-line
This function inserts spaces between the words of the current
line so that the line ends exactly at `fill-column'. It returns
`nil'.
* User Option: fill-column
This buffer-local variable specifies the maximum width of filled
lines. Its value should be an integer, which is a number of
columns. All the filling, justification and centering commands
are affected by this variable, including Auto Fill mode (*note
Auto Filling::.).
As a practical matter, if you are writing text for other people
to read, you should set `fill-column' to no more than 70.
Otherwise the line will be too long for people to read
comfortably, and this can make the text seem clumsy.
* Variable: default-fill-column
The value of this variable is the default value for
`fill-column' in buffers that do not override it. This is the
same as `(default-value 'fill-column)'.
The default value for `default-fill-column' is 70.
File: elisp, Node: Auto Filling, Next: Sorting, Prev: Filling, Up: Text
Auto Filling
============
"Filling" breaks text into lines that are no more than a specified
number of columns wide. Filled lines end between words, and
therefore may have to be shorter than the maximum width.
Auto Fill mode is a minor mode in which Emacs fills lines
automatically as text as inserted. This section describes the hook
and the two variables used by Auto Fill mode. For a description of
functions that you can call manually to fill and justify text, see
*Note Filling::.
* Variable: auto-fill-hook
The value of this variable should be a function (of no
arguments) to be called after self-inserting a space at a column
beyond `fill-column'. It may be `nil', in which case nothing
special is done.
The default value for `auto-fill-hook' is `do-auto-fill', a
function whose sole purpose is to implement the usual strategy
for breaking a line.
Since `auto-fill-hook' is not called by the `run-hooks'
function, it will be renamed `auto-fill-function' in Version 19.
File: elisp, Node: Sorting, Next: Indentation, Prev: Auto Filling, Up: Text
Sorting Text
============
The sorting commands described in this section all rearrange text
in a buffer. This is in contrast to the function `sort', which
rearranges the order of the elements of a list (*note
Rearrangement::.). The values returned by these commands are not
meaningful.
* Command: sort-regexp-fields REVERSE RECORD-REGEXP KEY-REGEXP START
END
This command sorts the region between START and END
alphabetically as specified by RECORD-REGEXP and KEY-REGEXP. If
REVERSE is a negative integer, then sorting is in reverse order.
Alphabetical sorting means that two sort keys are compared by
comparing the first characters of each, the second characters of
each, and so on. If a mismatch is found, it means that the sort
keys are unequal; the sort key whose character is less at the
point of first mismatch is the lesser sort key. The individual
characters are compared according to their numerical values.
Since Emacs uses the ASCII character set, the ordering in that
set determines alphabetical order.
The value of the RECORD-REGEXP argument specifies the textual
units or "records" that should be sorted. At the end of each
record, a search is done for this regular expression, and the
text that matches it is the next record. For example, the
regular expression `^.+$', which matches lines with at least one
character besides a newline, would make each such line into a
sort record. *Note Regular Expressions::, for a description of
the syntax and meaning of regular expressions.
The value of the KEY-REGEXP argument specifies what part of each
record is to be compared against the other records. The
KEY-REGEXP could match the whole record, or only a part. In the
latter case, the rest of the record has no effect on the sorted
order of records, but it is carried along when the record moves
to its new position.
The KEY-REGEXP argument can refer to the text matched by a
subexpression of RECORD-REGEXP, or it can be a regular
expression on its own.
If KEY-REGEXP is:
`\DIGIT'
then the text matched by the DIGITth `\(...\)' parenthesis
grouping in RECORD-REGEXP is used for sorting.
`\&'
then the whole record is used for sorting.
a regular expression
then the function searches for a match for the regular
expression within the record. If such a match is found, it
is used for sorting. If a match for KEY-REGEXP is not
found within a record then that record is ignored, which
means its position in the buffer is not changed. (The
other records may move around it.)
For example, if you plan to sort all the lines in the region by
the first word on each line starting with the letter `f', you
should set RECORD-REGEXP to `^.*$' and set KEY-REGEXP to
`\<f\w*\>'. The resulting expression looks like this:
(sort-regexp-fields nil "^.*$" "\\<f\\w*\\>"
(region-beginning)
(region-end))
If you call `sort-regexp-fields' interactively, you are prompted
for RECORD-REGEXP and KEY-REGEXP in the minibuffer.
* Command: sort-subr REVERSE NEXTRECFUN ENDRECFUN &optional
STARTKEYFUN ENDKEYFUN
This command is the general text sorting routine that divides a
buffer into records and sorts them. The functions `sort-lines',
`sort-paragraphs', `sort-pages', `sort-fields',
`sort-regexp-fields' and `sort-numeric-fields' all use
`sort-subr'.
To understand how `sort-subr' works, consider the whole
accessible portion of the buffer as being divided into disjoint
pieces called "sort records". A portion of each sort record
(perhaps all of it) is designated as the sort key. The records
are rearranged in the buffer in order by their sort keys. The
records may or may not be contiguous.
Usually, the records are rearranged in order of ascending sort
key. If the first argument to the `sort-subr' function,
REVERSE, is non-`nil', the sort records are rearranged in order
of descending sort key.
The next four arguments to `sort-subr' are functions that are
called to move point across a sort record. They are called many
times from within `sort-subr'.
1. NEXTRECFUN is called with point at the end of a record.
This function moves point to the start of the next record.
The first record is assumed to start at the position of
point when `sort-subr' is called. (Therefore, you should
usually move point to the beginning of the buffer before
calling `sort-subr'.)
2. ENDRECFUN is called with point within a record. It moves
point to the end of the record.
3. STARTKEYFUN is called to move point from the start of a
record to the start of the sort key. This argument is
optional. If supplied, the function should either return a
non-`nil' value to be used as the sort key, or return `nil'
to indicate that the sort key is in the buffer starting at
point. In the latter case, and ENDKEYFUN will be called to
find the end of the sort key.
4. ENDKEYFUN is called to move point from the start of the
sort key to the end of the sort key. This argument is
optional. If STARTKEYFUN returns `nil' and this argument
is omitted (or `nil'), then the sort key extends to the end
of the record. There is no need for ENDKEYFUN if
STARTKEYFUN returns a non-`nil' value.
As an example of `sort-subr', here is the complete function
definition for `sort-lines':
(defun sort-lines (reverse beg end)
"Sort lines in region alphabetically; arg means reverse order.
Called from a program, there are three arguments:
REVERSE (non-nil means reverse order),
and BEG and END (the region to sort)."
(interactive "P\nr")
(save-restriction
(narrow-to-region beg end)
(goto-char (point-min))
(sort-subr reverse 'forward-line 'end-of-line)))
Here `forward-line' moves point to the start of the next record,
and `end-of-line' moves point to the end of record. We do not
pass the arguments STARTKEYFUN and ENDKEYFUN, because the entire
record is used as the sort key.
The `sort-paragraphs' function is very much the same, except
that its `sort-subr' call looks like this:
(sort-subr reverse
(function (lambda () (skip-chars-forward "\n \t\f")))
'forward-paragraph)))
* Command: sort-lines REVERSE START END
This command sorts lines in the region between START and END
alphabetically. If REVERSE is non-`nil', the sort is in reverse
order.
* Command: sort-paragraphs REVERSE START END
This command sorts paragraphs in the region between START and
END alphabetically. If REVERSE is non-`nil', the sort is in
reverse order.
* Command: sort-pages REVERSE START END
This command sorts pages in the region between START and END
alphabetically. If REVERSE is non-`nil', the sort is in reverse
order.
* Command: sort-fields FIELD START END
This command sorts lines in the region between START and END,
comparing them alphabetically by the FIELDth field of each line.
Fields are separated by whitespace and numbered starting from 1.
If FIELD is negative, sorting is by the -FIELDth field from the
end of the line. This command is useful for sorting tables.
* Command: sort-numeric-fields FIELD START END
This command sorts lines in the region between START and END,
comparing them numerically by the FIELDth field of each line.
Fields are separated by whitespace and numbered starting from 1.
The specified field must contain a number in each line of the
region. If FIELD is negative, sorting is by the -FIELDth field
from the end of the line. This command is useful for sorting
tables.
* Command: sort-columns REVERSE &optional BEG END
This command sorts the lines in the region between BEG and END,
comparing them alphabetically by a certain range of columns.
For the purpose of this command, the region includes the entire
line that point is in and the entire line containing END. The
column positions of BEG and END bound the range of columns to
sort on.
If REVERSE is non-`nil', the sort is in reverse order.
One unusual thing about this command is that the entire line
containing point, and the entire line containing the mark, are
included in the region sorted.
Note that `sort-columns' uses the `sort' utility program, and so
cannot work properly on text containing tab characters. Use
`M-x `untabify'' to convert tabs to spaces before sorting. The
`sort-columns' function doesn't work in VMS, because the
subprocess facilities are lacking.
File: elisp, Node: Indentation, Next: Columns, Prev: Sorting, Up: Text
Indentation
===========
The indentation functions are used to examine, move to, and change
whitespace that is at the beginning of a line. Some of the functions
can also change whitespace elsewhere on a line. Indentation always
counts from zero at the left margin.
* Menu:
* Primitive Indent:: Functions used to count and insert indentation.
* Mode-Specific Indent:: Customize indentation for different modes.
* Region Indent:: Indent all the lines in a region.
* Relative Indent:: Indent the current line based on previous lines.
* Indent Tabs:: Adjustable, typewriter-like tab stops.
* Motion by Indent:: Move to first non-blank character.
File: elisp, Node: Primitive Indent, Next: Mode-Specific Indent, Prev: Indentation, Up: Indentation
Indentation Primitives
----------------------
This section describes the primitive functions used to count and
insert indentation. The functions in the following sections use
these primitives.
* Function: current-indentation
This function returns the indentation of the current line, which
is the horizontal position of the first nonblank character. If
the contents are entirely blank, then this is the horizontal
position of the end of the line.
* Command: indent-to COLUMN &optional MINIMUM
This function indents from point with tabs and spaces until
COLUMN is reached. If MINIMUM is specified and non-`nil', then
at least that many spaces are inserted even if this requires
going beyond COLUMN. The value is the column at which the
inserted indentation ends.
* User Option: indent-tabs-mode
If this variable is non-`nil', indentation functions can insert
tabs as well as spaces. Otherwise, they insert only spaces.
Setting this variable automatically makes it local to the
current buffer.
File: elisp, Node: Mode-Specific Indent, Next: Region Indent, Prev: Primitive Indent, Up: Indentation
Indentation Controlled by Major Mode
------------------------------------
An important function of each major mode is to customize the TAB
key to indent properly for the language being edited. This section
describes the mechanism of the TAB key and how to control it. The
functions in this section return unpredictable values.
* Variable: indent-line-function
This variable's value is the function to be used by TAB (and
various commands) to indent the current line. The command
`indent-according-to-mode' does no more than call this function.
In Lisp mode, the value is the symbol `lisp-indent-line'; in C
mode, `c-indent-line'; in Fortran mode, `fortran-indent-line'.
In Fundamental mode, Text mode, and many other modes with no
standard for indentation, the value is `indent-to-left-margin'
(which is the default value).
* Command: indent-according-to-mode
This command calls the function in `indent-line-function' to
indent the current line in a way appropriate for the current
major mode.
* Command: indent-for-tab-command
This command calls the function in `indent-line-function' to
indent the current line, except that if that function is
`indent-to-left-margin', `insert-tab' is called instead.
* Variable: left-margin
This variable is the column to which the default
`indent-line-function' will indent. (That function is
`indent-to-left-margin'.) In Fundamental mode, LFD indents to
this column. This variable automatically becomes buffer-local
when set in any fashion.
* Function: indent-to-left-margin
This is the default `indent-line-function', used in Fundamental
mode, Text mode, etc. Its effect is to adjust the indentation
at the beginning of the current line to the value specified by
the variable `left-margin'. This may involve either inserting
or deleting whitespace.
* Command: newline-and-indent
This function inserts a newline, then indents the new line (the
one following the newline just inserted) according to the major
mode.
Indentation is done using the current `indent-line-function'.
In programming language modes, this is the same thing TAB does,
but in some text modes, where TAB inserts a tab,
`newline-and-indent' indents to the column specified by
`left-margin'.
* Command: reindent-then-newline-and-indent
This command reindents the current line, inserts a newline at
point, and then reindents the new line (the one following the
newline just inserted).
Indentation of both lines is done according to the current major
mode; this means that the current value of
`indent-line-function' is called. In programming language
modes, this is the same thing TAB does, but in some text modes,
where TAB inserts a tab, `reindent-then-newline-and-indent'
indents to the column specified by `left-margin'.
File: elisp, Node: Region Indent, Next: Relative Indent, Prev: Mode-Specific Indent, Up: Indentation
Indenting an Entire Region
--------------------------
This section describes commands which indent all the lines in the
region. They return unpredictable values.
* Command: indent-region START END TO-COLUMN
This command indents each nonblank line starting between START
(inclusive) and END (exclusive). If TO-COLUMN is `nil',
`indent-region' indents each nonblank line by calling the
current mode's indentation function, the value of
`indent-line-function'.
If TO-COLUMN is non-`nil', it should be an integer specifying
the number of columns of indentation; then this function gives
each line exactly that much indentation, by either adding or
deleting whitespace.
* Variable: indent-region-function
The value of this variable is a function that can be used by
`indent-region' as a short cut. You should design the function
so that it will produce the same results as indenting the lines
of the region one by one (but presumably faster).
If the value is `nil', there is no short cut, and
`indent-region' actually works line by line.
A short cut function is useful in modes such as C mode and Lisp
mode, where the `indent-line-function' must scan from the
beginning of the function: applying it to each line would be
quadratic in time. The short cut can update the scan
information as it moves through the lines indenting them; this
takes linear time. If indenting a line individually is fast,
there is no need for a short cut.
`indent-region' with a non-`nil' argument has a different
definition and does not use this variable.
* Command: indent-rigidly START END COUNT
This command indents all lines starting between START
(inclusive) and END (exclusive) sideways by `count' columns.
This "preserves the shape" of the affected region, moving it as
a rigid unit. Consequently, this command is useful not only for
indenting regions of unindented text, but also for indenting
regions of formatted code.
For example, if COUNT is 3, this command adds 3 columns of
indentation to each of the lines beginning in the region
specified.
In Mail mode, `C-c C-y' (`mail-yank-original') uses
`indent-rigidly' to indent the text copied from the message
being replied to.
File: elisp, Node: Relative Indent, Next: Indent Tabs, Prev: Region Indent, Up: Indentation
Indentation Relative to Previous Lines
--------------------------------------
This section describes two commands which indent the current line
based on the contents of previous lines.
* Command: indent-relative &optional UNINDENTED-OK
This function inserts whitespace at point, extending to the same
column as the next "indent point" of the previous nonblank line.
An indent point is a non-whitespace character following
whitespace. The next indent point is the first one at a column
greater than the current column of point. For example, if point
is underneath and to the left of the first non-blank character
of a line of text, it moves to that column by inserting
whitespace.
If the previous nonblank line has no next indent point (i.e.,
none at a great enough column position), this function either
does nothing (if UNINDENTED-OK is non-`nil') or calls
`tab-to-tab-stop'. Thus, if point is underneath and to the
right of the last column of a short line of text, this function
moves point to the next tab stop by inserting whitespace.
This command returns an unpredictable value.
In the following example, point is at the beginning of the
second line:
This line is indented twelve spaces.
-!-The quick brown fox jumped over the lazy dog.
Evaluation of the expression `(indent-relative nil)' produces
the following:
This line is indented twelve spaces.
-!-The quick brown fox jumped over the lazy dog.
In this example, point is between the `m' and `p' of `jumped':
This line is indented twelve spaces.
The quick brown fox jum-!-ped over the lazy dog.
Evaluation of the expression `(indent-relative nil)' produces
the following:
This line is indented twelve spaces.
The quick brown fox jum -!-ped over the lazy dog.
* Command: indent-relative-maybe
This command indents the current line like the previous nonblank
line. The function consists of a call to `indent-relative' with
a non-`nil' value passed to the UNINDENTED-OK optional argument.
The value is unpredictable.
If the previous line has no indentation, the current line is
given no indentation (any existing indentation is deleted); if
the previous nonblank line has no indent points beyond the
column at which point starts, nothing is changed.