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This is Info file ../../info/lispref.info, produced by Makeinfo-1.63 from the input file lispref.texi. Edition History: GNU Emacs Lisp Reference Manual Second Edition (v2.01), May 1993 GNU Emacs Lisp Reference Manual Further Revised (v2.02), August 1993 Lucid Emacs Lisp Reference Manual (for 19.10) First Edition, March 1994 XEmacs Lisp Programmer's Manual (for 19.12) Second Edition, April 1995 GNU Emacs Lisp Reference Manual v2.4, June 1995 XEmacs Lisp Programmer's Manual (for 19.13) Third Edition, July 1995 Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Free Software Foundation, Inc. Copyright (C) 1994, 1995 Sun Microsystems, Inc. Copyright (C) 1995 Amdahl Corporation. Copyright (C) 1995 Ben Wing. 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. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the section entitled "GNU General Public License" is included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the section entitled "GNU General Public License" may be included in a translation approved by the Free Software Foundation instead of in the original English. File: lispref.info, Node: Screen Lines, Next: List Motion, Prev: Text Lines, Up: Motion Motion by Screen Lines ---------------------- The line functions in the previous section count text lines, delimited only by newline characters. By contrast, these functions count screen lines, which are defined by the way the text appears on the screen. A text line is a single screen line if it is short enough to fit the width of the selected window, but otherwise it may occupy several screen lines. In some cases, text lines are truncated on the screen rather than continued onto additional screen lines. In these cases, `vertical-motion' moves point much like `forward-line'. *Note Truncation::. Because the width of a given string depends on the flags that control the appearance of certain characters, `vertical-motion' behaves differently, for a given piece of text, depending on the buffer it is in, and even on the selected window (because the width, the truncation flag, and display table may vary between windows). *Note Usual Display::. These functions scan text to determine where screen lines break, and thus take time proportional to the distance scanned. If you intend to use them heavily, Emacs provides caches which may improve the performance of your code. *Note cache-long-line-scans: Text Lines. - Function: vertical-motion COUNT &optional WINDOW This function moves point to the start of the screen line COUNT screen lines down from the screen line containing point. If COUNT is negative, it moves up instead. `vertical-motion' returns the number of lines moved. The value may be less in absolute value than COUNT if the beginning or end of the buffer was reached. The window WINDOW is used for obtaining parameters such as the width, the horizontal scrolling, and the display table. But `vertical-motion' always operates on the current buffer, even if WINDOW currently displays some other buffer. - Command: move-to-window-line COUNT This function moves point with respect to the text currently displayed in the selected window. It moves point to the beginning of the screen line COUNT screen lines from the top of the window. If COUNT is negative, that specifies a position -COUNT lines from the bottom (or the last line of the buffer, if the buffer ends above the specified screen position). If COUNT is `nil', then point moves to the beginning of the line in the middle of the window. If the absolute value of COUNT is greater than the size of the window, then point moves to the place that would appear on that screen line if the window were tall enough. This will probably cause the next redisplay to scroll to bring that location onto the screen. In an interactive call, COUNT is the numeric prefix argument. The value returned is the window line number point has moved to, with the top line in the window numbered 0. File: lispref.info, Node: List Motion, Next: Skipping Characters, Prev: Screen Lines, Up: Motion Moving over Balanced Expressions -------------------------------- Here are several functions concerned with balanced-parenthesis expressions (also called "sexps" in connection with moving across them in XEmacs). The syntax table controls how these functions interpret various characters; see *Note Syntax Tables::. *Note Parsing Expressions::, for lower-level primitives for scanning sexps or parts of sexps. For user-level commands, see *Note Lists and Sexps: (emacs)Lists and Sexps. - Command: forward-list ARG This function moves forward across ARG balanced groups of parentheses. (Other syntactic entities such as words or paired string quotes are ignored.) - Command: backward-list ARG This function moves backward across ARG balanced groups of parentheses. (Other syntactic entities such as words or paired string quotes are ignored.) - Command: up-list ARG This function moves forward out of ARG levels of parentheses. A negative argument means move backward but still to a less deep spot. - Command: down-list ARG This function moves forward into ARG levels of parentheses. A negative argument means move backward but still go deeper in parentheses (-ARG levels). - Command: forward-sexp ARG This function moves forward across ARG balanced expressions. Balanced expressions include both those delimited by parentheses and other kinds, such as words and string constants. For example, ---------- Buffer: foo ---------- (concat-!- "foo " (car x) y z) ---------- Buffer: foo ---------- (forward-sexp 3) => nil ---------- Buffer: foo ---------- (concat "foo " (car x) y-!- z) ---------- Buffer: foo ---------- - Command: backward-sexp ARG This function moves backward across ARG balanced expressions. - Command: beginning-of-defun ARG This function moves back to the ARGth beginning of a defun. If ARG is negative, this actually moves forward, but it still moves to the beginning of a defun, not to the end of one. - Command: end-of-defun ARG This function moves forward to the ARGth end of a defun. If ARG is negative, this actually moves backward, but it still moves to the end of a defun, not to the beginning of one. - User Option: defun-prompt-regexp If non-`nil', this variable holds a regular expression that specifies what text can appear before the open-parenthesis that starts a defun. That is to say, a defun begins on a line that starts with a match for this regular expression, followed by a character with open-parenthesis syntax. File: lispref.info, Node: Skipping Characters, Prev: List Motion, Up: Motion Skipping Characters ------------------- The following two functions move point over a specified set of characters. For example, they are often used to skip whitespace. For related functions, see *Note Motion and Syntax::. - Function: skip-chars-forward CHARACTER-SET &optional LIMIT This function moves point in the current buffer forward, skipping over a given set of characters. It examines the character following point, then advances point if the character matches CHARACTER-SET. This continues until it reaches a character that does not match. The function returns `nil'. The argument CHARACTER-SET is like the inside of a `[...]' in a regular expression except that `]' is never special and `\' quotes `^', `-' or `\'. Thus, `"a-zA-Z"' skips over all letters, stopping before the first nonletter, and `"^a-zA-Z'" skips nonletters stopping before the first letter. *Note Regular Expressions::. If LIMIT is supplied (it must be a number or a marker), it specifies the maximum position in the buffer that point can be skipped to. Point will stop at or before LIMIT. In the following example, point is initially located directly before the `T'. After the form is evaluated, point is located at the end of that line (between the `t' of `hat' and the newline). The function skips all letters and spaces, but not newlines. ---------- Buffer: foo ---------- I read "-!-The cat in the hat comes back" twice. ---------- Buffer: foo ---------- (skip-chars-forward "a-zA-Z ") => nil ---------- Buffer: foo ---------- I read "The cat in the hat-!- comes back" twice. ---------- Buffer: foo ---------- - Function: skip-chars-backward CHARACTER-SET &optional LIMIT This function moves point backward, skipping characters that match CHARACTER-SET, until LIMIT. It just like `skip-chars-forward' except for the direction of motion. File: lispref.info, Node: Excursions, Next: Narrowing, Prev: Motion, Up: Positions 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 "excursion", and it is done with the `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. The forms for saving and restoring the configuration of windows are described elsewhere (see *Note Window Configurations::). - Special Form: save-excursion FORMS... The `save-excursion' special form saves the identity of the current buffer and the values of point and the mark in it, evaluates FORMS, 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 `throw' or error (*note Nonlocal Exits::.). The `save-excursion' special form is the standard way to switch buffers or move point within one part of a program and avoid affecting the rest of the program. It is used more than 500 times in the Lisp sources of XEmacs. `save-excursion' does not save the values of point and the mark for other buffers, so changes in other buffers remain in effect after `save-excursion' exits. Likewise, `save-excursion' does not restore window-buffer correspondences altered by functions such as `switch-to-buffer'. One way to restore these correspondences, and the selected window, is to use `save-window-excursion' inside `save-excursion' (*note Window Configurations::.). The value returned by `save-excursion' is the result of the last of FORMS, or `nil' if no FORMS are given. (save-excursion FORMS) == (let ((old-buf (current-buffer)) (old-pnt (point-marker)) (old-mark (copy-marker (mark-marker)))) (unwind-protect (progn FORMS) (set-buffer old-buf) (goto-char old-pnt) (set-marker (mark-marker) old-mark))) File: lispref.info, Node: Narrowing, Prev: Excursions, Up: Positions Narrowing ========= "Narrowing" means limiting the text addressable by XEmacs editing commands to a limited range of characters in a buffer. The text that remains addressable is called the "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 the entire buffer regardless of any narrowing. - Command: narrow-to-region START END This function sets the accessible portion of the current buffer to start at START and end at END. Both arguments should be character positions. In an interactive call, START and END are set to the bounds of the current region (point and the mark, with the smallest first). - Command: narrow-to-page MOVE-COUNT This function sets the accessible portion of the current buffer to include just the current page. An optional first argument MOVE-COUNT non-`nil' means to move forward or backward by MOVE-COUNT pages and then narrow. The variable `page-delimiter' specifies where pages start and end (*note Standard Regexps::.). In an interactive call, MOVE-COUNT is set to the numeric prefix argument. - Command: widen This function cancels any narrowing in the current buffer, so that the entire contents are accessible. This is called "widening". It is equivalent to the following expression: (narrow-to-region 1 (1+ (buffer-size))) - Special Form: save-restriction BODY... This special form saves the current bounds of the accessible portion, evaluates the BODY forms, and finally restores the saved bounds, thus restoring the same state of narrowing (or absence thereof) formerly in effect. The state of narrowing is restored even in the event of an abnormal exit via `throw' or error (*note Nonlocal Exits::.). Therefore, this construct is a clean way to narrow a buffer temporarily. The value returned by `save-restriction' is that returned by the last form in BODY, or `nil' if no body forms were given. *Caution:* it is easy to make a mistake when using the `save-restriction' construct. Read the entire description here before you try it. If BODY changes the current buffer, `save-restriction' still restores the restrictions on the original buffer (the buffer whose restructions it saved from), but it does not restore the identity of the current buffer. `save-restriction' does *not* restore point and the mark; use `save-excursion' for that. If you use both `save-restriction' and `save-excursion' together, `save-excursion' should come first (on the outside). Otherwise, the old point value would be restored with temporary narrowing still in effect. If the old point value were outside the limits of the temporary narrowing, this would fail to restore it accurately. The `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 BODY does further narrowing. However, `save-restriction' can become confused if the body widens and then make changes outside the range of the saved narrowing. When this is what you want to do, `save-restriction' is not the right tool for the job. Here is what you must use instead: (let ((beg (point-min-marker)) (end (point-max-marker))) (unwind-protect (progn BODY) (save-excursion (set-buffer (marker-buffer beg)) (narrow-to-region beg end)))) Here is a simple example of correct use of `save-restriction': ---------- Buffer: foo ---------- This is the contents of foo This is the contents of foo This is the contents of foo-!- ---------- Buffer: foo ---------- (save-excursion (save-restriction (goto-char 1) (forward-line 2) (narrow-to-region 1 (point)) (goto-char (point-min)) (replace-string "foo" "bar"))) ---------- Buffer: foo ---------- This is the contents of bar This is the contents of bar This is the contents of foo-!- ---------- Buffer: foo ---------- File: lispref.info, Node: Markers, Next: Text, Prev: Positions, Up: Top Markers ******* A "marker" is a Lisp object used to specify a position in a buffer relative to the surrounding text. A marker changes its offset from the beginning of the buffer automatically whenever text is inserted or deleted, so that it stays with the two characters on either side of it. * Menu: * Overview of Markers:: The components of a marker, and how it relocates. * Predicates on Markers:: Testing whether an object is a marker. * Creating Markers:: Making empty markers or markers at certain places. * Information from Markers:: Finding the marker's buffer or character position. * Changing Markers:: Moving the marker to a new buffer or position. * The Mark:: How "the mark" is implemented with a marker. * The Region:: How to access "the region". File: lispref.info, Node: Overview of Markers, Next: Predicates on Markers, Up: Markers Overview of Markers =================== A marker specifies a buffer and a position in that buffer. The marker can be used to represent a position in the functions that require one, just as an integer could be used. *Note Positions::, for a complete description of positions. A marker has two attributes: the marker position, and the marker buffer. The marker position is an integer that is equivalent (at a given time) to the marker as a position in that buffer. But the marker's position value can change often during the life of the marker. Insertion and deletion of text in the buffer relocate the marker. The idea is that a marker positioned between two characters remains between those two characters despite insertion and deletion elsewhere in the buffer. Relocation changes the integer equivalent of the marker. Deleting text around a marker's position leaves the marker between the characters immediately before and after the deleted text. Inserting text at the position of a marker normally leaves the marker in front of the new text--unless it is inserted with `insert-before-markers' (*note Insertion::.). Insertion and deletion in a buffer must check all the markers and relocate them if necessary. This slows processing in a buffer with a large number of markers. For this reason, it is a good idea to make a marker point nowhere if you are sure you don't need it any more. Unreferenced markers are garbage collected eventually, but until then will continue to use time if they do point somewhere. Because it is common to perform arithmetic operations on a marker position, most of the arithmetic operations (including `+' and `-') accept markers as arguments. In such cases, the marker stands for its current position. Here are examples of creating markers, setting markers, and moving point to markers: ;; Make a new marker that initially does not point anywhere: (setq m1 (make-marker)) => #<marker in no buffer> ;; Set `m1' to point between the 99th and 100th characters ;; in the current buffer: (set-marker m1 100) => #<marker at 100 in markers.texi> ;; Now insert one character at the beginning of the buffer: (goto-char (point-min)) => 1 (insert "Q") => nil ;; `m1' is updated appropriately. m1 => #<marker at 101 in markers.texi> ;; Two markers that point to the same position ;; are not `eq', but they are `equal'. (setq m2 (copy-marker m1)) => #<marker at 101 in markers.texi> (eq m1 m2) => nil (equal m1 m2) => t ;; When you are finished using a marker, make it point nowhere. (set-marker m1 nil) => #<marker in no buffer> File: lispref.info, Node: Predicates on Markers, Next: Creating Markers, Prev: Overview of Markers, Up: Markers Predicates on Markers ===================== You can test an object to see whether it is a marker, or whether it is either an integer or a marker. The latter test is useful in connection with the arithmetic functions that work with both markers and integers. - Function: markerp OBJECT This function returns `t' if OBJECT is a marker, `nil' otherwise. Note that integers are not markers, even though many functions will accept either a marker or an integer. - Function: integer-or-marker-p OBJECT This function returns `t' if OBJECT is an integer or a marker, `nil' otherwise. - Function: number-or-marker-p OBJECT This function returns `t' if OBJECT is a number (either kind) or a marker, `nil' otherwise. File: lispref.info, Node: Creating Markers, Next: Information from Markers, Prev: Predicates on Markers, Up: Markers Functions That Create Markers ============================= When you create a new marker, you can make it point nowhere, or point to the present position of point, or to the beginning or end of the accessible portion of the buffer, or to the same place as another given marker. - Function: make-marker This functions returns a newly created marker that does not point anywhere. (make-marker) => #<marker in no buffer> - Function: point-marker This function returns a new marker that points to the present position of point in the current buffer. *Note Point::. For an example, see `copy-marker', below. - Function: point-min-marker This function returns a new marker that points to the beginning of the accessible portion of the buffer. This will be the beginning of the buffer unless narrowing is in effect. *Note Narrowing::. - Function: point-max-marker This function returns a new marker that points to the end of the accessible portion of the buffer. This will be the end of the buffer unless narrowing is in effect. *Note Narrowing::. Here are examples of this function and `point-min-marker', shown in a buffer containing a version of the source file for the text of this chapter. (point-min-marker) => #<marker at 1 in markers.texi> (point-max-marker) => #<marker at 15573 in markers.texi> (narrow-to-region 100 200) => nil (point-min-marker) => #<marker at 100 in markers.texi> (point-max-marker) => #<marker at 200 in markers.texi> - Function: copy-marker MARKER-OR-INTEGER If passed a marker as its argument, `copy-marker' returns a new marker that points to the same place and the same buffer as does MARKER-OR-INTEGER. If passed an integer as its argument, `copy-marker' returns a new marker that points to position MARKER-OR-INTEGER in the current buffer. If passed an integer argument less than 1, `copy-marker' returns a new marker that points to the beginning of the current buffer. If passed an integer argument greater than the length of the buffer, `copy-marker' returns a new marker that points to the end of the buffer. An error is signaled if MARKER is neither a marker nor an integer. (setq p (point-marker)) => #<marker at 2139 in markers.texi> (setq q (copy-marker p)) => #<marker at 2139 in markers.texi> (eq p q) => nil (equal p q) => t (copy-marker 0) => #<marker at 1 in markers.texi> (copy-marker 20000) => #<marker at 7572 in markers.texi> File: lispref.info, Node: Information from Markers, Next: Changing Markers, Prev: Creating Markers, Up: Markers Information from Markers ======================== This section describes the functions for accessing the components of a marker object. - Function: marker-position MARKER This function returns the position that MARKER points to, or `nil' if it points nowhere. - Function: marker-buffer MARKER This function returns the buffer that MARKER points into, or `nil' if it points nowhere. (setq m (make-marker)) => #<marker in no buffer> (marker-position m) => nil (marker-buffer m) => nil (set-marker m 3770 (current-buffer)) => #<marker at 3770 in markers.texi> (marker-buffer m) => #<buffer markers.texi> (marker-position m) => 3770 Two distinct markers are considered `equal' (even though not `eq') to each other if they have the same position and buffer, or if they both point nowhere. File: lispref.info, Node: Changing Markers, Next: The Mark, Prev: Information from Markers, Up: Markers Changing Marker Positions ========================= This section describes how to change the position of an existing marker. When you do this, be sure you know whether the marker is used outside of your program, and, if so, what effects will result from moving it--otherwise, confusing things may happen in other parts of Emacs. - Function: set-marker MARKER POSITION &optional BUFFER This function moves MARKER to POSITION in BUFFER. If BUFFER is not provided, it defaults to the current buffer. If POSITION is less than 1, `set-marker' moves MARKER to the beginning of the buffer. If POSITION is greater than the size of the buffer, `set-marker' moves marker to the end of the buffer. If POSITION is `nil' or a marker that points nowhere, then MARKER is set to point nowhere. The value returned is MARKER. (setq m (point-marker)) => #<marker at 4714 in markers.texi> (set-marker m 55) => #<marker at 55 in markers.texi> (setq b (get-buffer "foo")) => #<buffer foo> (set-marker m 0 b) => #<marker at 1 in foo> - Function: move-marker MARKER POSITION &optional BUFFER This is another name for `set-marker'. File: lispref.info, Node: The Mark, Next: The Region, Prev: Changing Markers, Up: Markers The Mark ======== One special marker in each buffer is designated "the mark". It records a position for the user for the sake of commands such as `C-w' and `C-x TAB'. Lisp programs should set the mark only to values that have a potential use to the user, and never for their own internal purposes. For example, the `replace-regexp' command sets the mark to the value of point before doing any replacements, because this enables the user to move back there conveniently after the replace is finished. Many commands are designed so that when called interactively they operate on the text between point and the mark. If you are writing such a command, don't examine the mark directly; instead, use `interactive' with the `r' specification. This provides the values of point and the mark as arguments to the command in an interactive call, but permits other Lisp programs to specify arguments explicitly. *Note Interactive Codes::. Each buffer has its own value of the mark that is independent of the value of the mark in other buffers. When a buffer is created, the mark exists but does not point anywhere. We consider this state as "the absence of a mark in that buffer." Once the mark "exists" in a buffer, it normally never ceases to exist. However, it may become "inactive", if Transient Mark mode is enabled. The variable `mark-active', which is always local in all buffers, indicates whether the mark is active: non-`nil' means yes. A command can request deactivation of the mark upon return to the editor command loop by setting `deactivate-mark' to a non-`nil' value (but this causes deactivation only if Transient Mark mode is enabled). The main motivation for using Transient Mark mode is that this mode also enables highlighting of the region when the mark is active. *Note Display::. In addition to the mark, each buffer has a "mark ring" which is a list of markers containing previous values of the mark. When editing commands change the mark, they should normally save the old value of the mark on the mark ring. The variable `mark-ring-max' specifies the maximum number of entries in the mark ring; once the list becomes this long, adding a new element deletes the last element. - Function: mark &optional FORCE This function returns the current buffer's mark position as an integer. If the mark is inactive, `mark' normally signals an error. However, if FORCE is non-`nil', then `mark' returns the mark position anyway--or `nil', if the mark is not yet set for this buffer. - Function: mark-marker This function returns the current buffer's mark. This is the very marker that records the mark location inside XEmacs, not a copy. Therefore, changing this marker's position will directly affect the position of the mark. Don't do it unless that is the effect you want. (setq m (mark-marker)) => #<marker at 3420 in markers.texi> (set-marker m 100) => #<marker at 100 in markers.texi> (mark-marker) => #<marker at 100 in markers.texi> Like any marker, this marker can be set to point at any buffer you like. We don't recommend that you make it point at any buffer other than the one of which it is the mark. If you do, it will yield perfectly consistent, but rather odd, results. - Function: set-mark POSITION This function sets the mark to POSITION, and activates the mark. The old value of the mark is *not* pushed onto the mark ring. *Please note:* Use this function only if you want the user to see that the mark has moved, and you want the previous mark position to be lost. Normally, when a new mark is set, the old one should go on the `mark-ring'. For this reason, most applications should use `push-mark' and `pop-mark', not `set-mark'. Novice Emacs Lisp programmers often try to use the mark for the wrong purposes. The mark saves a location for the user's convenience. An editing command should not alter the mark unless altering the mark is part of the user-level functionality of the command. (And, in that case, this effect should be documented.) To remember a location for internal use in the Lisp program, store it in a Lisp variable. For example: (let ((beg (point))) (forward-line 1) (delete-region beg (point))). - Function: push-mark &optional POSITION NOMSG ACTIVATE This function sets the current buffer's mark to POSITION, and pushes a copy of the previous mark onto `mark-ring'. If POSITION is `nil', then the value of point is used. `push-mark' returns `nil'. The function `push-mark' normally *does not* activate the mark. To do that, specify `t' for the argument ACTIVATE. A `Mark set' message is displayed unless NOMSG is non-`nil'. - Function: pop-mark This function pops off the top element of `mark-ring' and makes that mark become the buffer's actual mark. This does not move point in the buffer, and it does nothing if `mark-ring' is empty. It deactivates the mark. The return value is not meaningful. - User Option: transient-mark-mode This variable if non-`nil' enables Transient Mark mode, in which every buffer-modifying primitive sets `deactivate-mark'. The consequence of this is that commands that modify the buffer normally make the mark inactive. - Variable: deactivate-mark If an editor command sets this variable non-`nil', then the editor command loop deactivates the mark after the command returns, but only if Transient Mark mode is enabled. - Function: deactivate-mark This function deactivates the mark, but only if Transient Mark mode is enabled. - Variable: mark-active The mark is active when this variable is non-`nil'. This variable is always local in each buffer. - Variable: activate-mark-hook - Variable: deactivate-mark-hook These normal hooks are run, respectively, when the mark becomes active and when it becomes inactive. The hook `activate-mark-hook' is also run at the end of a command if the mark is active and the region may have changed. - Variable: mark-ring The value of this buffer-local variable is the list of saved former marks of the current buffer, most recent first. mark-ring => (#<marker at 11050 in markers.texi> #<marker at 10832 in markers.texi> ...) - User Option: mark-ring-max The value of this variable is the maximum size of `mark-ring'. If more marks than this are pushed onto the `mark-ring', `push-mark' discards an old mark when it adds a new one. File: lispref.info, Node: The Region, Prev: The Mark, Up: Markers The Region ========== The text between point and the mark is known as "the region". Various functions operate on text delimited by point and the mark, but only those functions specifically related to the region itself are described here. - Function: region-beginning This function returns the position of the beginning of the region (as an integer). This is the position of either point or the mark, whichever is smaller. If the mark does not point anywhere, an error is signaled. - Function: region-end This function returns the position of the end of the region (as an integer). This is the position of either point or the mark, whichever is larger. If the mark does not point anywhere, an error is signaled. Few programs need to use the `region-beginning' and `region-end' functions. A command designed to operate on a region should normally use `interactive' with the `r' specification to find the beginning and end of the region. This lets other Lisp programs specify the bounds explicitly as arguments. (*Note Interactive Codes::.) File: lispref.info, Node: Text, Next: Searching and Matching, Prev: Markers, Up: Top Text **** This chapter describes the functions that deal with the text in a buffer. Most examine, insert, or delete text in the current buffer, often in the vicinity of point. Many are interactive. All the functions that change the text provide for undoing the changes (*note Undo::.). Many text-related functions operate on a region of text defined by two buffer positions passed in arguments named START and END. These arguments should be either markers (*note Markers::.) or numeric character positions (*note Positions::.). The order of these arguments does not matter; it is all right for START to be the end of the region and END the beginning. For example, `(delete-region 1 10)' and `(delete-region 10 1)' are equivalent. An `args-out-of-range' error is signaled if either START or END is outside the accessible portion of the buffer. In an interactive call, point and the mark are used for these arguments. Throughout this chapter, "text" refers to the characters in the buffer, together with their properties (when relevant). * Menu: * Near Point:: Examining text in the vicinity of point. * Buffer Contents:: Examining text in a general fashion. * Comparing Text:: Comparing substrings of buffers. * Insertion:: Adding new text to a buffer. * Commands for Insertion:: User-level commands to insert text. * Deletion:: Removing text from a buffer. * User-Level Deletion:: User-level commands to delete text. * The Kill Ring:: Where removed text sometimes is saved for later use. * Undo:: Undoing changes to the text of a buffer. * Maintaining Undo:: How to enable and disable undo information. How to control how much information is kept. * Filling:: Functions for explicit filling. * Margins:: How to specify margins for filling commands. * Auto Filling:: How auto-fill mode is implemented to break lines. * Sorting:: Functions for sorting parts of the buffer. * Columns:: Computing horizontal positions, and using them. * Indentation:: Functions to insert or adjust indentation. * Case Changes:: Case conversion of parts of the buffer. * Text Properties:: Assigning Lisp property lists to text characters. * Substitution:: Replacing a given character wherever it appears. * Transposition:: Swapping two portions of a buffer. * Registers:: How registers are implemented. Accessing the text or position stored in a register. * Change Hooks:: Supplying functions to be run when text is changed. File: lispref.info, Node: Near Point, Next: Buffer Contents, Up: Text Examining Text Near Point ========================= Many functions are provided to look at the characters around point. Several simple functions are described here. See also `looking-at' in *Note Regexp Search::. Many of these functions take an optional BUFFER argument. In all such cases, the current buffer will be used if this argument is omitted. (In FSF Emacs, and earlier versions of XEmacs, these functions usually did not have these optional BUFFER arguments and always operated on the current buffer.) - Function: char-after POSITION &optional BUFFER This function returns the character in the buffer at (i.e., immediately after) position POSITION. If POSITION is out of range for this purpose, either before the beginning of the buffer, or at or beyond the end, then the value is `nil'. If optional argument BUFFER is `nil', the current buffer is assumed. In the following example, assume that the first character in the buffer is `@': (char-to-string (char-after 1)) => "@" - Function: following-char &optional BUFFER This function returns the character following point in the buffer. This is similar to `(char-after (point))'. However, if point is at the end of the buffer, then the result of `following-char' is 0. If optional argument BUFFER is `nil', the current buffer is assumed. Remember that point is always between characters, and the terminal cursor normally appears over the character following point. Therefore, the character returned by `following-char' is the character the cursor is over. In this example, point is between the `a' and the `c'. ---------- Buffer: foo ---------- Gentlemen may cry ``Pea-!-ce! Peace!,'' but there is no peace. ---------- Buffer: foo ---------- (char-to-string (preceding-char)) => "a" (char-to-string (following-char)) => "c" - Function: preceding-char &optional BUFFER This function returns the character preceding point in the buffer. buffer. See above, under `following-char', for an example. If point is at the beginning of the buffer, `preceding-char' returns 0. If optional argument BUFFER is `nil', the current buffer is assumed. - Function: bobp &optional BUFFER This function returns `t' if point is at the beginning of the buffer. If narrowing is in effect, this means the beginning of the accessible portion of the text. If optional argument BUFFER is `nil', the current buffer is assumed. See also `point-min' in *Note Point::. - Function: eobp &optional BUFFER This function returns `t' if point is at the end of the buffer. If narrowing is in effect, this means the end of accessible portion of the text. If optional argument BUFFER is `nil', the current buffer is assumed. See also `point-max' in *Note Point::. - Function: bolp &optional BUFFER This function returns `t' if point is at the beginning of a line. If optional argument BUFFER is `nil', the current buffer is assumed. *Note Text Lines::. The beginning of the buffer (or its accessible portion) always counts as the beginning of a line. - Function: eolp &optional BUFFER This function returns `t' if point is at the end of a line. The end of the buffer is always considered the end of a line. If optional argument BUFFER is `nil', the current buffer is assumed. The end of the buffer (or of its accessible portion) is always considered the end of a line. File: lispref.info, Node: Buffer Contents, Next: Comparing Text, Prev: Near Point, Up: Text Examining Buffer Contents ========================= This section describes two functions that allow a Lisp program to convert any portion of the text in the buffer into a string. - Function: buffer-substring START END &optional BUFFER This function returns a string containing a copy of the text of the region defined by positions START and END in the buffer. If the arguments are not positions in the accessible portion of the buffer, `buffer-substring' signals an `args-out-of-range' error. If optional argument BUFFER is `nil', the current buffer is assumed. If the region delineated by START and END contains duplicable extents, they will be remembered in the string.*Note Duplicable Extents::. It is not necessary for START to be less than END; the arguments can be given in either order. But most often the smaller argument is written first. ---------- Buffer: foo ---------- This is the contents of buffer foo ---------- Buffer: foo ---------- (buffer-substring 1 10) => "This is t" (buffer-substring (point-max) 10) => "he contents of buffer foo " - Function: buffer-substring-without-properties START END This is like `buffer-substring', except that it does not copy text properties, just the characters themselves. *Note Text Properties::. Here's an example of using this function to get a word to look up in an alist: (setq flammable (assoc (buffer-substring start end) '(("wood" . t) ("paper" . t) ("steel" . nil) ("asbestos" . nil)))) If this were written using `buffer-substring' instead, it would not work reliably; any text properties that happened to be in the word copied from the buffer would make the comparisons fail. - Function: buffer-string This function returns the contents of the accessible portion of the current buffer as a string. This is the portion between `(point-min)' and `(point-max)' (*note Narrowing::.). ---------- Buffer: foo ---------- This is the contents of buffer foo ---------- Buffer: foo ---------- (buffer-string) => "This is the contents of buffer foo " File: lispref.info, Node: Comparing Text, Next: Insertion, Prev: Buffer Contents, Up: Text Comparing Text ============== This function lets you compare portions of the text in a buffer, without copying them into strings first. - Function: compare-buffer-substrings BUFFER1 START1 END1 BUFFER2 START2 END2 This function lets you compare two substrings of the same buffer or two different buffers. The first three arguments specify one substring, giving a buffer and two positions within the buffer. The last three arguments specify the other substring in the same way. You can use `nil' for BUFFER1, BUFFER2, or both to stand for the current buffer. The value is negative if the first substring is less, positive if the first is greater, and zero if they are equal. The absolute value of the result is one plus the index of the first differing characters within the substrings. This function ignores case when comparing characters if `case-fold-search' is non-`nil'. It always ignores text properties. Suppose the current buffer contains the text `foobarbar haha!rara!'; then in this example the two substrings are `rbar ' and `rara!'. The value is 2 because the first substring is greater at the second character. (compare-buffer-substring nil 6 11 nil 16 21) => 2 File: lispref.info, Node: Insertion, Next: Commands for Insertion, Prev: Comparing Text, Up: Text Inserting Text ============== "Insertion" means adding new text to a buffer. The inserted text goes at point--between the character before point and the character after point. Insertion relocates markers that point at positions after the insertion point, so that they stay with the surrounding text (*note Markers::.). When a marker points at the place of insertion, insertion normally doesn't relocate the marker, so that it points to the beginning of the inserted text; however, certain special functions such as `insert-before-markers' relocate such markers to point after the inserted text. Some insertion functions leave point before the inserted text, while other functions leave it after. We call the former insertion "after point" and the latter insertion "before point". If a string with non-`nil' extent data is inserted, the remembered extents will also be inserted. *Note Duplicable Extents::. Insertion functions signal an error if the current buffer is read-only. These functions copy text characters from strings and buffers along with their properties. The inserted characters have exactly the same properties as the characters they were copied from. By contrast, characters specified as separate arguments, not part of a string or buffer, inherit their text properties from the neighboring text. - Function: insert &rest ARGS This function inserts the strings and/or characters ARGS into the current buffer, at point, moving point forward. In other words, it inserts the text before point. An error is signaled unless all ARGS are either strings or characters. The value is `nil'. - Function: insert-before-markers &rest ARGS This function inserts the strings and/or characters ARGS into the current buffer, at point, moving point forward. An error is signaled unless all ARGS are either strings or characters. The value is `nil'. This function is unlike the other insertion functions in that it relocates markers initially pointing at the insertion point, to point after the inserted text. - Function: insert-char CHARACTER COUNT &optional BUFFER This function inserts COUNT instances of CHARACTER into BUFFER before point. COUNT must be a number, and CHARACTER must be a character. The value is `nil'. If optional argument BUFFER is `nil', the current buffer is assumed. (In FSF Emacs, the third argument is called INHERIT and refers to text properties.) - Function: insert-buffer-substring FROM-BUFFER-OR-NAME &optional START END This function inserts a portion of buffer FROM-BUFFER-OR-NAME (which must already exist) into the current buffer before point. The text inserted is the region from START and END. (These arguments default to the beginning and end of the accessible portion of that buffer.) This function returns `nil'. In this example, the form is executed with buffer `bar' as the current buffer. We assume that buffer `bar' is initially empty. ---------- Buffer: foo ---------- We hold these truths to be self-evident, that all ---------- Buffer: foo ---------- (insert-buffer-substring "foo" 1 20) => nil ---------- Buffer: bar ---------- We hold these truth-!- ---------- Buffer: bar ----------