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This is Info file elisp, produced by Makeinfo-1.55 from the input file
elisp.texi.
This is edition 2.0 of the GNU Emacs Lisp Reference Manual, for
Emacs Version 19.
Published by the Free Software Foundation, 675 Massachusetts Avenue,
Cambridge, MA 02139 USA
Copyright (C) 1990, 1991, 1992, 1993 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: 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:
* Kill Ring Concepts:: What text looks like in the kill ring.
* Kill Functions:: Functions that kill text.
* Yank Commands:: Commands that access the kill ring.
* Low Level Kill Ring:: Functions and variables for kill ring access.
* Internals of Kill Ring:: Variables that hold kill-ring data.
File: elisp, Node: Kill Ring Concepts, Next: Kill Functions, Up: The Kill Ring
Kill Ring Concepts
------------------
The kill ring records killed text 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")
New entries in the kill ring go at the front of the list. When the
list reaches `kill-ring-max' entries in length, adding a new entry
automatically deletes the last entry.
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 succession, the text they
kill forms a single entry, because the second and subsequent consecutive
kill commands append to the entry made by the first one.
The user can reinsert or "yank" text from any element in the kill
ring. One of the entries in the ring is considered the "front", and
the simplest yank command yanks that entry. Other yank commands
"rotate" the ring by designating other entries as the "front".
File: elisp, Node: Kill Functions, Next: Yank Commands, Prev: Kill Ring Concepts, Up: The Kill Ring
Functions for Killing
---------------------
`kill-region' is the usual subroutine for killing text. Any command
that calls this function is a "kill command" (and should probably have
`kill' in its name). `kill-region' puts the newly killed text in a new
element at the beginning of the kill ring or adds it to the most recent
element. It 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.
- 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.
If the buffer is read-only, `kill-region' modifies the kill ring
just the same, then signals an error without modifying the buffer.
This is convenient because it lets the user use all the kill
commands to copy text into the kill ring from a read-only buffer.
- 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'. It also indicates the extent of the text copied by
moving the cursor momentarily, or by displaying a message in the
echo area.
Don't use this command in Lisp programs; use `kill-new' or
`kill-append' instead. *Note Low Level Kill Ring::.
In an interactive call, START and END are point and the mark.
File: elisp, Node: Yank Commands, Next: Low Level Kill Ring, 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 ARGth 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: Low Level Kill Ring, Next: Internals of Kill Ring, Prev: Yank Commands, Up: The Kill Ring
Low Level Kill Ring
-------------------
These functions and variables provide access to the kill ring at a
lower level, but still convenient for use in Lisp programs. They take
care of interaction with X Window selections. They do not exist in
Emacs version 18.
- Function: current-kill N &optional DO-NOT-MOVE
The function `current-kill' rotates the yanking pointer in the
kill ring by N places, and returns the text at that place in the
ring.
If the optional second argument DO-NOT-MOVE is non-`nil', then
`current-kill' doesn't alter the yanking pointer; it just returns
the Nth kill forward from the current yanking pointer.
If N is zero, indicating a request for the latest kill,
`current-kill' calls the value of `interprogram-paste-function'
(documented below) before consulting the kill ring.
- Function: kill-new STRING
This function puts the text STRING into the kill ring as a new
entry at the front of the ring. It also discards the oldest entry
if appropriate. It also invokes the value of
`interprogram-cut-function' (see below).
- Function: kill-append STRING BEFORE-P
This function appends the text STRING to the first entry in the
kill ring. Normally STRING goes at the end of the entry, but if
BEFORE-P is non-`nil', it goes at the beginning. This function
also invokes the value of `interprogram-cut-function' (see below).
- Variable: interprogram-paste-function
This variable provides a way of transferring killed text from other
programs, when you are using a window system. Its value should be
`nil' or a function of no arguments.
If the value is a function, it is called when the "most recent
kill" value is called for. If the function returns a non-`nil'
values, then that value is used as the "most recent kill". If it
returns `nil', then the first element of the kill ring is used.
- Variable: interprogram-cut-function
This variable provides a way of communicating killed text to and
from other programs, when you are using a window system. Its
value should be `nil' or a function of one argument.
If the value is a function, it is called whenever the "most recent
kill" is changed, with the new string of killed text as an
argument.
File: elisp, Node: Internals of Kill Ring, Prev: Low Level Kill Ring, Up: The Kill Ring
Internals of the Kill Ring
--------------------------
The variable `kill-ring' holds the kill ring contents, in the form
of a list of strings. The most recent kill is always at the front of
the list.
The `kill-ring-yank-pointer' variable points to a link in the kill
ring list, whose CAR is the text that "yank" functions should copy.
Moving `kill-ring-yank-pointer' to a different link is called "rotating
the kill ring". We call the kill ring a "ring" because the functions
that move the yank pointer wrap around from the end of the list to the
beginning, or vice-versa. Rotating the ring does not change the value
of `kill-ring'.
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 for use 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. Commands which change the text in the kill ring also set
this variable from `kill-ring'. The effect is to rotate the ring so
that the newly killed text is at front.
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 might occur after `C-y' (`yank') immediately followed
by `M-y' (`yank-pop').
- 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
at the "front" of the ring for yanking. More precisely, the value
is a sublist of the value of `kill-ring', and its CAR is the kill
string that `C-y' should yank.
- 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 at the end. The
default value for `kill-ring-max' is 30.
File: elisp, Node: Undo, Next: Maintaining Undo, Prev: The Kill Ring, Up: Text
Most buffers have an "undo list" which records all changes made to
the buffer's text so that they can be undone. (The buffers which don't
have one are usually special-purpose buffers for which Emacs assumes
that undoing is not useful.) All the primitives which modify the text
in the buffer automatically add elements to the front of the undo list,
which you can find in the variable `buffer-undo-list'.
- Variable: buffer-undo-list
This variable's value is the undo list of the current buffer. A
value of `t' disables the recording of undo information.
Here are the kinds of elements an undo list can have:
`INTEGER'
This kind of element records a previous value of point. Ordinary
cursor motion does not get any sort of undo record, but these
entries are used to record where point was before a deletion.
`(BEG . END)'
This kind of element indicates how to delete text that was
inserted. Upon insertion, the text occupied the range BEG-END in
the buffer.
`(POS . DELETED)'
This kind of element indicates how to reinsert text that was
deleted. The deleted text itself is the string DELETED. The
place to reinsert it is POS.
`(t HIGH . LOW)'
This kind of element indicates that an unmodified buffer became
modified. The elements HIGH and LOW are two integers, each
recording 16 bits of the visited file's modification time as of
when it was previously visited or saved. `primitive-undo' uses
those values to determine whether to mark the buffer as unmodified
once again; it does so only if the file's modification time
matches those numbers.
`(nil PROPERTY VALUE BEG . END)'
This kind of element records a change in a text property. Here's
how you might undo the change:
(put-text-property BEG END
PROPERTY VALUE)
`nil'
This element is a boundary. The function `undo-boundary' adds
these elements. The elements between two boundaries are called a
"change group"; normally, each change group corresponds to one
keyboard command, and undo commands normally undo an entire group
as a unit.
- Function: undo-boundary
This function places a boundary element in the undo list. The undo
command stops at such a boundary, and successive undo commands undo
to earlier and earlier boundaries. This function returns `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: primitive-undo COUNT LIST
This is the basic function for undoing elements of an undo list.
It undoes the first COUNT elements of LIST, returning the rest of
LIST. You could write this function in Lisp, but it is convenient
to have it in C.
`primitive-undo' adds elements to the buffer's undo list. Undo
commands avoid confusion by saving the undo list value at the
beginning of a sequence of undo operations. Then the undo
operations use and update the saved value. The new elements added
by undoing never get into the saved value, so they don't cause any
trouble.
File: elisp, Node: Maintaining Undo, Next: Auto Filling, Prev: Undo, Up: Text
Maintaining Undo Lists
======================
This section describes how to enable and disable undo information for
a given buffer. It also explains how data from the undo list is
discarded automatically so it doesn't get too big.
Recording of undo information in a newly created buffer is normally
enabled to start with; but if the buffer name starts with a space, the
undo recording is initially disabled. You can explicitly enable or
disable undo recording with the following two functions, or by setting
`buffer-undo-list' yourself.
- Command: buffer-enable-undo &optional BUFFER-OR-NAME
This function enables recording undo information for buffer
BUFFER-OR-NAME, so that subsequent changes can be undone. If no
argument is supplied, then the current buffer is used. This
function does nothing if undo recording is already enabled in the
buffer. It returns `nil'.
In an interactive call, BUFFER-OR-NAME is the current buffer. You
cannot specify any other buffer.
- Function: buffer-disable-undo BUFFER
- Function: buffer-flush-undo BUFFER
This function discards the undo list of BUFFER, and disables
further recording of undo information. As a result, it is no
longer possible to undo either previous changes or any subsequent
changes. If the undo list of BUFFER is already disabled, this
function has no effect.
This function returns `nil'. It cannot be called interactively.
The name `buffer-flush-undo' is not considered obsolete, but the
preferred name `buffer-disable-undo' was not provided in Emacs
versions 18 and earlier.
As editing continues, undo lists get longer and longer. To prevent
them from using up all available memory space, garbage collection trims
them back to size limits you can set. (For this purpose, the "size" of
an undo list measures the cons cells that make up the list, plus the
strings of deleted text.) Two variables control the range of acceptable
sizes: `undo-limit' and `undo-strong-limit'.
- Variable: undo-limit
This is the soft limit for the acceptable size of an undo list.
The change group at which this size is exceeded is the last one
kept.
- Variable: undo-strong-limit
The upper limit for the acceptable size of an undo list. The
change group at which this size is exceeded is discarded itself
(along with all subsequent changes). There is one exception:
garbage collection always keeps the very last change group no
matter how big it is.
File: elisp, Node: Filling, Next: Sorting, Prev: Auto Filling, 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. It
uses the ordinary paragraph motion commands to find paragraph
boundaries.
- 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.
Ordinarily, `fill-individual-paragraphs' regards each change in
indentation as starting a new paragraph. If
`fill-individual-varying-indent' is non-`nil', then only separator
lines separate paragraphs. That mode can handle paragraphs with
extra indentation on the first line.
- User Option: fill-individual-varying-indent
This variable alters the action of `fill-individual-paragraphs' as
described above.
- 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.
In Adaptive Fill mode, which is enabled by default,
`fill-region-as-paragraph' on an indented paragraph when there is
no fill prefix uses the indentation of the second line of the
paragraph as the fill prefix.
- 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: Filling, Prev: Maintaining Undo, 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-function
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-function' is `do-auto-fill', a
function whose sole purpose is to implement the usual strategy for
breaking a line.
In older Emacs versions, this variable was named
`auto-fill-hook', but since it is not called with the
standard convention for hooks, it was renamed to
`auto-fill-function' in version 19.
File: elisp, Node: Sorting, Next: Indentation, Prev: 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'.)
This function can indicate there are no more sort records by
leaving point at the end of the buffer.
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, ENDKEYFUN is 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':
;; Note that the first two lines of doc string
;; are effectively one line when viewed by a user.
(defun sort-lines (reverse beg end)
"Sort lines in region alphabetically;\
argument means descending 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. 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 position BEG, and the entire line containing position
END, 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 did not work on VMS prior to Emacs 19.
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, 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. (That is
a trivial command which inserts a tab character.)
- 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.
If there is a fill prefix, `indent-region' indents each line by
making it start with the fill prefix.
- 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.
- Function: indent-code-rigidly START END COLUMNS &optional
NOCHANGE-REGEXP
This is like `indent-rigidly', except that it doesn't alter lines
that start within strings or comments.
In addition, it doesn't alter a line if NOCHANGE-REGEXP matches at
the beginning of the line (if NOCHANGE-REGEXP is non-`nil').
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.
Evaluation of the expression `(indent-relative nil)' produces the
following:
This line is indented twelve spaces.
-!-The quick brown fox jumped.
In this example, point is between the `m' and `p' of `jumped':
This line is indented twelve spaces.
The quick brown fox jum-!-ped.
Evaluation of the expression `(indent-relative nil)' produces the
following:
This line is indented twelve spaces.
The quick brown fox jum -!-ped.
- 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.
File: elisp, Node: Indent Tabs, Next: Motion by Indent, Prev: Relative Indent, Up: Indentation
Adjustable "Tab Stops"
----------------------
This section explains the mechanism for user-specified "tab stops"
and the mechanisms which use and set them. The name "tab stops" is
used because the feature is similar to that of the tab stops on a
typewriter. The feature works by inserting an appropriate number of
spaces and tab characters to reach the designated position, like the
other indentation functions; it does not affect the display of tab
characters in the buffer (*note Usual Display::.). Note that the TAB
character as input uses this tab stop feature only in a few major
modes, such as Text mode.
- Function: tab-to-tab-stop
This function inserts spaces or tabs up to the next tab stop column
defined by `tab-stop-list'. It searches the list for an element
greater than the current column number, and uses that element as
the column to indent to. If no such element is found, then
nothing is done.
- User Option: tab-stop-list
This variable is the list of tab stop columns used by
`tab-to-tab-stops'. The elements should be integers in increasing
order. The tab stop columns need not be evenly spaced.
Use `M-x edit-tab-stops' to edit the location of tab stops
interactively.
File: elisp, Node: Motion by Indent, Prev: Indent Tabs, Up: Indentation
Indentation-Based Motion Commands
---------------------------------
These commands, primarily for interactive use, act based on the
indentation in the text.
- Command: back-to-indentation
This command moves point to the first non-whitespace character in
the current line (which is the line in which point is located).
It returns `nil'.
- Command: backward-to-indentation ARG
This command moves point backward ARG lines and then to the first
nonblank character on that line. It returns `nil'.
- Command: forward-to-indentation ARG
This command moves point forward ARG lines and then to the first
nonblank character on that line. It returns `nil'.
File: elisp, Node: Columns, Next: Case Changes, Prev: Indentation, Up: Text
Counting Columns
================
The column functions convert between a character position (counting
characters from the beginning of the buffer) and a column position
(counting screen characters from the beginning of a line).
Column number computations ignore the width of the window and the
amount of horizontal scrolling. Consequently, a column value can be
arbitrarily high. The first (or leftmost) column is numbered 0.
A character counts according to the number of columns it occupies on
the screen. This means control characters count as occupying 2 or 4
columns, depending upon the value of `ctl-arrow', and tabs count as
occupying a number of columns that depends on the value of `tab-width'
and on the column where the tab begins. *Note Usual Display::.
- Function: current-column
This function returns the horizontal position of point, measured in
columns, counting from 0 at the left margin. The column count is
calculated by adding together the widths of all the displayed
representations of the characters between the start of the current
line and point.
For a more complicated example of the use of `current-column', see
the description of `count-lines' in *Note Text Lines::.
- Function: move-to-column COLUMN &optional FORCE
This function moves point to COLUMN in the current line. The
calculation of COLUMN takes into account the widths of all the
displayed representations of the characters between the start of
the line and point.
If the argument COLUMN is greater than the column position of the
end of the line, point moves to the end of the line. If COLUMN is
negative, point moves to the beginning of the line.
If it is impossible to move to column COLUMN because that is in
the middle of a multicolumn character such as a tab, point moves
to the end of that character. However, if FORCE is non-`nil', and
COLUMN is in the middle of a tab, then `move-to-column' converts
the tab into spaces so that it can move precisely to column COLUMN.
The argument FORCE also has an effect if the line isn't long
enough to reach column COLUMN; in that case, it says to indent at
the end of the line to reach that column.
If COLUMN is not an integer, an error is signaled.
The return value is the column number actually moved to.