@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998 Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000
+@c Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/positions
@node Positions, Markers, Frames, Top
automatically when text is inserted or deleted so they stay with the
surrounding characters. @xref{Markers}.
+ See also the ``field'' feature (@pxref{Fields}), which provides
+functions that are used by many cursur-motion commands.
+
@menu
* Point:: The special position where editing takes place.
* Motion:: Changing point.
the character on which the cursor sits.
@cindex point with narrowing
- The value of point is a number between 1 and the buffer size plus 1.
-If narrowing is in effect (@pxref{Narrowing}), then point is constrained
-to fall within the accessible portion of the buffer (possibly at one end
-of it).
+ The value of point is a number no less than 1, and no greater than the
+buffer size plus 1. If narrowing is in effect (@pxref{Narrowing}), then
+point is constrained to fall within the accessible portion of the buffer
+(possibly at one end of it).
Each buffer has its own value of point, which is independent of the
value of point in other buffers. Each window also has a value of point,
This function returns the maximum accessible value of point in the
current buffer. This is @code{(1+ (buffer-size))}, unless narrowing is
in effect, in which case it is the position of the end of the region
-that you narrowed to. (@xref{Narrowing}).
+that you narrowed to. (@xref{Narrowing}.)
@end defun
@defun buffer-end flag
@code{(point-max)} otherwise. The argument @var{flag} must be a number.
@end defun
-@defun buffer-size
+@defun buffer-size &optional buffer
This function returns the total number of characters in the current
buffer. In the absence of any narrowing (@pxref{Narrowing}),
@code{point-max} returns a value one larger than this.
+If you specify a buffer, @var{buffer}, then the value is the
+size of @var{buffer}.
+
@example
@group
(buffer-size)
@deffn Command forward-word count
This function moves point forward @var{count} words (or backward if
-@var{count} is negative). More precisely, it keeps moving until it
-moves across a word-constituent character and encounters a
-word-separator character, then returns @code{t}.
-
-If this motion encounters the beginning or end of the buffer, or the
-limits of the accessible portion when narrowing is in effect, point
-stops there and the value is @code{nil}.
-
-In an interactive call, @var{count} is set to the numeric prefix
+@var{count} is negative). ``Moving one word'' means moving until point
+crosses a word-constituent character and then encounters a
+word-separator character. However, this function cannot move point past
+the boundary of the accessible part of the buffer, or across a field
+boundary (@pxref{Fields}). The most common case of a field boundary is
+the end of the prompt in the minibuffer.
+
+If it is possible to move @var{count} words, without being stopped
+prematurely by the buffer boundary or a field boundary, the value is
+@code{t}. Otherwise, the return value is @code{nil} and point stops at
+the buffer boundary or field boundary.
+
+If @code{inhibit-field-text-motion} is non-@code{nil},
+this function ignores field boundaries.
+
+In an interactive call, @var{count} is specified by the numeric prefix
argument.
@end deffn
In an interactive call, @var{count} is set to the numeric prefix
argument.
-This function is rarely used in programs, as it is more efficient to
-call @code{forward-word} with a negative argument.
+@c [Now optimized by compiler.]
+@c This function is rarely used in programs, as it is more efficient to
+@c call @code{forward-word} with a negative argument.
@end deffn
@defvar words-include-escapes
words. Otherwise, they do not.
@end defvar
+@defvar inhibit-field-text-motion
+@tindex inhibit-field-text-motion
+If this variable is non-@code{nil}, certain motion functions including
+@code{forward-word}, @code{forward-sentence}, and
+@code{forward-paragraph} ignore field boundaries.
+@end defvar
+
@node Buffer End Motion
@subsection Motion to an End of the Buffer
This function moves point to the beginning of the buffer (or the limits
of the accessible portion, when narrowing is in effect), setting the
mark at the previous position. If @var{n} is non-@code{nil}, then it
-puts point @var{n} tenths of the way from the beginning of the buffer.
+puts point @var{n} tenths of the way from the beginning of the
+accessible portion of the buffer.
In an interactive call, @var{n} is the numeric prefix argument,
if provided; otherwise @var{n} defaults to @code{nil}.
@end deffn
@deffn Command end-of-buffer &optional n
-This function moves point to the end of the buffer (or the limits of
-the accessible portion, when narrowing is in effect), setting the mark
-at the previous position. If @var{n} is non-@code{nil}, then it puts
-point @var{n} tenths of the way from the end of the buffer.
+This function moves point to the end of the buffer (or the limits of the
+accessible portion, when narrowing is in effect), setting the mark at
+the previous position. If @var{n} is non-@code{nil}, then it puts point
+@var{n} tenths of the way from the end of the accessible portion of the
+buffer.
In an interactive call, @var{n} is the numeric prefix argument,
if provided; otherwise @var{n} defaults to @code{nil}.
is signaled.
@end deffn
+@defun line-beginning-position &optional count
+@tindex line-beginning-position
+Return the position that @code{(beginning-of-line @var{count})}
+would move to.
+@end defun
+
@deffn Command end-of-line &optional count
This function moves point to the end of the current line. With an
argument @var{count} not @code{nil} or 1, it moves forward
is signaled.
@end deffn
+@defun line-end-position &optional count
+@tindex line-end-position
+Return the position that @code{(end-of-line @var{count})}
+would move to.
+@end defun
+
@deffn Command forward-line &optional count
@cindex beginning of line
This function moves point forward @var{count} lines, to the beginning of
them in Emacs). The syntax table controls how these functions interpret
various characters; see @ref{Syntax Tables}. @xref{Parsing
Expressions}, for lower-level primitives for scanning sexps or parts of
-sexps. For user-level commands, see @ref{Lists Commands,,, emacs, GNU
+sexps. For user-level commands, see @ref{Lists Commands,,, emacs, The GNU
Emacs Manual}.
-@deffn Command forward-list arg
-This function moves forward across @var{arg} balanced groups of
+@deffn Command forward-list &optional arg
+This function moves forward across @var{arg} (default 1) balanced groups of
parentheses. (Other syntactic entities such as words or paired string
quotes are ignored.)
@end deffn
-@deffn Command backward-list arg
-This function moves backward across @var{arg} balanced groups of
+@deffn Command backward-list &optional arg
+This function moves backward across @var{arg} (default 1) balanced groups of
parentheses. (Other syntactic entities such as words or paired string
quotes are ignored.)
@end deffn
-@deffn Command up-list arg
-This function moves forward out of @var{arg} levels of parentheses.
+@deffn Command up-list &optional arg
+This function moves forward out of @var{arg} (default 1) levels of parentheses.
A negative argument means move backward but still to a less deep spot.
@end deffn
-@deffn Command down-list arg
-This function moves forward into @var{arg} levels of parentheses. A
+@deffn Command down-list &optional arg
+This function moves forward into @var{arg} (default 1) levels of parentheses. A
negative argument means move backward but still go
deeper in parentheses (@minus{}@var{arg} levels).
@end deffn
-@deffn Command forward-sexp arg
-This function moves forward across @var{arg} balanced expressions.
+@deffn Command forward-sexp &optional arg
+This function moves forward across @var{arg} (default 1) balanced expressions.
Balanced expressions include both those delimited by parentheses and
other kinds, such as words and string constants. For example,
@end example
@end deffn
-@deffn Command backward-sexp arg
-This function moves backward across @var{arg} balanced expressions.
+@deffn Command backward-sexp &optional arg
+This function moves backward across @var{arg} (default 1) balanced expressions.
@end deffn
@deffn Command beginning-of-defun arg
open-parenthesis syntax.
@end defopt
+@defvar beginning-of-defun-function
+@tindex beginning-of-defun-function
+If non-@code{nil}, this variable holds a function for finding the
+beginning of a defun. The function @code{beginning-of-defun}
+calls this function instead of using its normal method.
+@end defvar
+
+@defvar end-of-defun-function
+@tindex end-of-defun-function
+If non-@code{nil}, this variable holds a function for finding the end of
+a defun. The function @code{end-of-defun} calls this function instead
+of using its normal method.
+@end defvar
+
@node Skipping Characters
@comment node-name, next, previous, up
@subsection Skipping Characters
given set of characters. It examines the character following point,
then advances point if the character matches @var{character-set}. This
continues until it reaches a character that does not match. The
-function returns @code{nil}.
+function returns the number of characters moved over.
The argument @var{character-set} is like the inside of a
@samp{[@dots{}]} in a regular expression except that @samp{]} is never
This function moves point backward, skipping characters that match
@var{character-set}, until @var{limit}. It is just like
@code{skip-chars-forward} except for the direction of motion.
+
+The return value indicates the distance traveled. It is an integer that
+is zero or less.
@end defun
@node Excursions
It is often useful to move point ``temporarily'' within a localized
portion of the program, or to switch buffers temporarily. This is
called an @dfn{excursion}, and it is done with the @code{save-excursion}
-special form. This construct saves the current buffer and its values of
-point and the mark so they can be restored after the completion of the
-excursion.
+special form. This construct initially remembers the identity of the
+current buffer, and its values of point and the mark, and restores them
+after the completion of the excursion.
The forms for saving and restoring the configuration of windows are
described elsewhere (see @ref{Window Configurations}, and @pxref{Frame
@example
@group
-(save-excursion
- @var{forms})
+(save-excursion @var{forms})
@equiv{}
(let ((old-buf (current-buffer))
(old-pnt (point-marker))
+@end group
(old-mark (copy-marker (mark-marker))))
(unwind-protect
(progn @var{forms})
(set-buffer old-buf)
+@group
(goto-char old-pnt)
(set-marker (mark-marker) old-mark)))
@end group
@strong{Warning:} Ordinary insertion of text adjacent to the saved
point value relocates the saved value, just as it relocates all markers.
Therefore, when the saved point value is restored, it normally comes
-after the inserted text.
+before the inserted text.
Although @code{save-excursion} saves the location of the mark, it does
not prevent functions which modify the buffer from setting
value were outside the limits of the temporary narrowing, this would
fail to restore it accurately.
-The @code{save-restriction} special form records the values of the
-beginning and end of the accessible portion as distances from the
-beginning and end of the buffer. In other words, it records the amount
-of inaccessible text before and after the accessible portion.
-
-This method yields correct results if @var{body} does further narrowing.
-However, @code{save-restriction} can become confused if the body widens
-and then makes changes outside the range of the saved narrowing. When
-this is what you want to do, @code{save-restriction} is not the right
-tool for the job. Here is what you must use instead:
-
-@example
-@group
-(let ((beg (point-min-marker))
- (end (point-max-marker)))
- (unwind-protect
- (progn @var{body})
- (save-excursion
- (set-buffer (marker-buffer beg))
- (narrow-to-region beg end))))
-@end group
-@end example
-
Here is a simple example of correct use of @code{save-restriction}:
@example
HCoop / bpt / emacs.git / blobdiff