@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000, 2001,
-@c 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
+@c Copyright (C) 1990-1995, 1998-2013 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
-@setfilename ../../info/positions
-@node Positions, Markers, Frames, Top
+@node Positions
@chapter Positions
@cindex position (in buffer)
1, even if @var{start} and @var{end} are on the same line. This is
because the text between them, considered in isolation, must contain at
least one line unless it is empty.
+@end defun
-Here is an example of using @code{count-lines}:
+@deffn Command count-words start end
+@cindex words in region
+This function returns the number of words between the positions
+@var{start} and @var{end} in the current buffer.
-@example
-@group
-(defun current-line ()
- "Return the vertical position of point@dots{}"
- (+ (count-lines (window-start) (point))
- (if (= (current-column) 0) 1 0)))
-@end group
-@end example
-@end defun
+This function can also be called interactively. In that case, it
+prints a message reporting the number of lines, words, and characters
+in the buffer, or in the region if the region is active.
+@end deffn
@defun line-number-at-pos &optional pos
@cindex line number
@end defun
@node List Motion
-@comment node-name, next, previous, up
@subsection Moving over Balanced Expressions
@cindex sexp motion
@cindex Lisp expression motion
@end defvar
@node Skipping Characters
-@comment node-name, next, previous, up
@subsection Skipping Characters
@cindex skipping characters
Thus, @code{"a-zA-Z"} skips over all letters, stopping before the
first nonletter, and @code{"^a-zA-Z"} skips nonletters stopping before
the first letter. See @xref{Regular Expressions}. Character classes
-can also be used, e.g. @code{"[:alnum:]"}. See @pxref{Char Classes}.
+can also be used, e.g., @code{"[:alnum:]"}. See @pxref{Char Classes}.
If @var{limit} is supplied (it must be a number or a marker), it
specifies the maximum position in the buffer that point can be skipped
@cindex excursion
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 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
-Configurations}). When only the identity of the current buffer needs
-to be saved and restored, it is preferable to use
-@code{save-current-buffer} instead.
+portion of the program. This is called an @dfn{excursion}, and it is
+done with the @code{save-excursion} special form. This construct
+remembers the initial identity of the current buffer, and its values
+of point and the mark, and restores them after the excursion
+completes. It is the standard way to move point within one part of a
+program and avoid affecting the rest of the program, and is used
+thousands of times in the Lisp sources of Emacs.
+
+ If you only need to save and restore the identity of the current
+buffer, use @code{save-current-buffer} or @code{with-current-buffer}
+instead (@pxref{Current Buffer}). If you need to save or restore
+window configurations, see the forms described in @ref{Window
+Configurations} and in @ref{Frame Configurations}.
@defspec save-excursion body@dots{}
@cindex mark excursion
@cindex point excursion
-The @code{save-excursion} special form saves the identity of the current
-buffer and the values of point and the mark in it, evaluates
-@var{body}, and finally restores the buffer and its saved values of
-point and the mark. All three saved values are restored even in case of
-an abnormal exit via @code{throw} or error (@pxref{Nonlocal Exits}).
+This special form saves the identity of the current buffer and the
+values of point and the mark in it, evaluates @var{body}, and finally
+restores the buffer and its saved values of point and the mark. All
+three saved values are restored even in case of an abnormal exit via
+@code{throw} or error (@pxref{Nonlocal Exits}).
-The @code{save-excursion} special form is the standard way to move
-point within one part of a program and avoid affecting the rest of the
-program. It is used more than 4000 times in the Lisp sources
-of Emacs.
+The value returned by @code{save-excursion} is the result of the last
+form in @var{body}, or @code{nil} if no body forms were given.
+@end defspec
-@code{save-excursion} does not save the values of point and the mark for
-other buffers, so changes in other buffers remain in effect after
-@code{save-excursion} exits.
+ Because @code{save-excursion} only saves point and mark for the
+buffer that was current at the start of the excursion, any changes
+made to point and/or mark in other buffers, during the excursion, will
+remain in effect afterward. This frequently leads to unintended
+consequences, so the byte compiler warns if you call @code{set-buffer}
+during an excursion:
-@cindex window excursions
-Likewise, @code{save-excursion} does not restore window-buffer
-correspondences altered by functions such as @code{switch-to-buffer}.
-One way to restore these correspondences, and the selected window, is to
-use @code{save-window-excursion} inside @code{save-excursion}
-(@pxref{Window Configurations}).
+@example
+Warning: Use `with-current-buffer' rather than
+ save-excursion+set-buffer
+@end example
-The value returned by @code{save-excursion} is the result of the last
-form in @var{body}, or @code{nil} if no body forms were given.
+@noindent
+To avoid such problems, you should call @code{save-excursion} only
+after setting the desired current buffer, as in the following example:
@example
@group
-(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)))
+(defun append-string-to-buffer (string buffer)
+ "Append STRING to the end of BUFFER."
+ (with-current-buffer buffer
+ (save-excursion
+ (goto-char (point-max))
+ (insert string))))
@end group
@end example
-@end defspec
+
+@cindex window excursions
+ Likewise, @code{save-excursion} does not restore window-buffer
+correspondences altered by functions such as @code{switch-to-buffer}.
@strong{Warning:} Ordinary insertion of text adjacent to the saved
-point value relocates the saved value, just as it relocates all markers.
-More precisely, the saved value is a marker with insertion type
-@code{nil}. @xref{Marker Insertion Types}. Therefore, when the saved
-point value is restored, it normally comes before the inserted text.
+point value relocates the saved value, just as it relocates all
+markers. More precisely, the saved value is a marker with insertion
+type @code{nil}. @xref{Marker Insertion Types}. Therefore, when the
+saved point value is restored, it normally comes 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
remains addressable is called the @dfn{accessible portion} of the
buffer.
- Narrowing is specified with two buffer positions which become the
-beginning and end of the accessible portion. For most editing commands
-and most Emacs primitives, these positions replace the values of the
-beginning and end of the buffer. While narrowing is in effect, no text
-outside the accessible portion is displayed, and point cannot move
-outside the accessible portion.
-
- Values such as positions or line numbers, which usually count from the
-beginning of the buffer, do so despite narrowing, but the functions
-which use them refuse to operate on text that is inaccessible.
-
- The commands for saving buffers are unaffected by narrowing; they save
+ Narrowing is specified with two buffer positions, which become the
+beginning and end of the accessible portion. For most editing
+commands and primitives, these positions replace the values of the
+beginning and end of the buffer. While narrowing is in effect, no
+text outside the accessible portion is displayed, and point cannot
+move outside the accessible portion. Note that narrowing does not
+alter actual buffer positions (@pxref{Point}); it only determines
+which positions are considered the accessible portion of the buffer.
+Most functions refuse to operate on text that is outside the
+accessible portion.
+
+ Commands for saving buffers are unaffected by narrowing; they save
the entire buffer regardless of any narrowing.
If you need to display in a single buffer several very different
@end example
@end deffn
+@defun buffer-narrowed-p
+This function returns non-@code{nil} if the buffer is narrowed, and
+@code{nil} otherwise.
+@end defun
+
@defspec save-restriction body@dots{}
This special form saves the current bounds of the accessible portion,
evaluates the @var{body} forms, and finally restores the saved bounds,
@end group
@end example
@end defspec
-
-@ignore
- arch-tag: 56e8ff26-4ffe-4832-a141-7e991a2d0f87
-@end ignore
HCoop / bpt / emacs.git / blobdiff