[bpt/emacs.git] / lisp / subr.el

;;; subr.el --- basic lisp subroutines for Emacs

;; Copyright (C) 1985, 86, 92, 94, 95, 99, 2000, 2001
;;   Free Software Foundation, Inc.

;; This file is part of GNU Emacs.

;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING.  If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Commentary:

;;; Code:
(defvar custom-declare-variable-list nil
  "Record `defcustom' calls made before `custom.el' is loaded to handle them.
Each element of this list holds the arguments to one call to `defcustom'.")

;; Use this, rather than defcustom, in subr.el and other files loaded
;; before custom.el.
(defun custom-declare-variable-early (&rest arguments)
  (setq custom-declare-variable-list
	(cons arguments custom-declare-variable-list)))
\f
;;;; Lisp language features.

(defalias 'not 'null)

(defmacro lambda (&rest cdr)
  "Return a lambda expression.
A call of the form (lambda ARGS DOCSTRING INTERACTIVE BODY) is
self-quoting; the result of evaluating the lambda expression is the
expression itself.  The lambda expression may then be treated as a
function, i.e., stored as the function value of a symbol, passed to
funcall or mapcar, etc.

ARGS should take the same form as an argument list for a `defun'.
DOCSTRING is an optional documentation string.
 If present, it should describe how to call the function.
 But documentation strings are usually not useful in nameless functions.
INTERACTIVE should be a call to the function `interactive', which see.
It may also be omitted.
BODY should be a list of lisp expressions."
  ;; Note that this definition should not use backquotes; subr.el should not
  ;; depend on backquote.el.
  (list 'function (cons 'lambda cdr)))

(defmacro push (newelt listname)
  "Add NEWELT to the list stored in the symbol LISTNAME.
This is equivalent to (setq LISTNAME (cons NEWELT LISTNAME)).
LISTNAME must be a symbol."
  (list 'setq listname
	(list 'cons newelt listname)))

(defmacro pop (listname)
  "Return the first element of LISTNAME's value, and remove it from the list.
LISTNAME must be a symbol whose value is a list.
If the value is nil, `pop' returns nil but does not actually
change the list."
  (list 'prog1 (list 'car listname)
	(list 'setq listname (list 'cdr listname))))

(defmacro when (cond &rest body)
  "If COND yields non-nil, do BODY, else return nil."
  (list 'if cond (cons 'progn body)))

(defmacro unless (cond &rest body)
  "If COND yields nil, do BODY, else return nil."
  (cons 'if (cons cond (cons nil body))))

(defmacro dolist (spec &rest body)
  "(dolist (VAR LIST [RESULT]) BODY...): loop over a list.
Evaluate BODY with VAR bound to each car from LIST, in turn.
Then evaluate RESULT to get return value, default nil."
  (let ((temp (make-symbol "--dolist-temp--")))
    (list 'let (list (list temp (nth 1 spec)) (car spec))
	  (list 'while temp
		(list 'setq (car spec) (list 'car temp))
		(cons 'progn
		      (append body
			      (list (list 'setq temp (list 'cdr temp))))))
	  (if (cdr (cdr spec))
	      (cons 'progn
		    (cons (list 'setq (car spec) nil) (cdr (cdr spec))))))))

(defmacro dotimes (spec &rest body)
  "(dotimes (VAR COUNT [RESULT]) BODY...): loop a certain number of times.
Evaluate BODY with VAR bound to successive integers running from 0,
inclusive, to COUNT, exclusive.  Then evaluate RESULT to get
the return value (nil if RESULT is omitted)."
  (let ((temp (make-symbol "--dotimes-temp--")))
    (list 'let (list (list temp (nth 1 spec)) (list (car spec) 0))
	   (list 'while (list '< (car spec) temp)
		 (cons 'progn
		       (append body (list (list 'setq (car spec)
						(list '1+ (car spec)))))))
	   (if (cdr (cdr spec))
	       (car (cdr (cdr spec)))
	     nil))))

(defsubst caar (x)
  "Return the car of the car of X."
  (car (car x)))

(defsubst cadr (x)
  "Return the car of the cdr of X."
  (car (cdr x)))

(defsubst cdar (x)
  "Return the cdr of the car of X."
  (cdr (car x)))

(defsubst cddr (x)
  "Return the cdr of the cdr of X."
  (cdr (cdr x)))

(defun last (x &optional n)
  "Return the last link of the list X.  Its car is the last element.
If X is nil, return nil.
If N is non-nil, return the Nth-to-last link of X.
If N is bigger than the length of X, return X."
  (if n
      (let ((m 0) (p x))
	(while (consp p)
	  (setq m (1+ m) p (cdr p)))
	(if (<= n 0) p
	  (if (< n m) (nthcdr (- m n) x) x)))
    (while (consp (cdr x))
      (setq x (cdr x)))
    x))

(defun butlast (x &optional n)
  "Returns a copy of LIST with the last N elements removed."
  (if (and n (<= n 0)) x
    (nbutlast (copy-sequence x) n)))

(defun nbutlast (x &optional n)
  "Modifies LIST to remove the last N elements."
  (let ((m (length x)))
    (or n (setq n 1))
    (and (< n m)
	 (progn
	   (if (> n 0) (setcdr (nthcdr (- (1- m) n) x) nil))
	   x))))

(defun remove (elt seq)
  "Return a copy of SEQ with all occurrences of ELT removed.
SEQ must be a list, vector, or string.  The comparison is done with `equal'."
  (if (nlistp seq)
      ;; If SEQ isn't a list, there's no need to copy SEQ because
      ;; `delete' will return a new object.
      (delete elt seq)
    (delete elt (copy-sequence seq))))

(defun remq (elt list)
  "Return a copy of LIST with all occurences of ELT removed.
The comparison is done with `eq'."
  (if (memq elt list)
      (delq elt (copy-sequence list))
    list))

(defun assoc-default (key alist &optional test default)
  "Find object KEY in a pseudo-alist ALIST.
ALIST is a list of conses or objects.  Each element (or the element's car,
if it is a cons) is compared with KEY by evaluating (TEST (car elt) KEY).
If that is non-nil, the element matches;
then `assoc-default' returns the element's cdr, if it is a cons,
or DEFAULT if the element is not a cons.

If no element matches, the value is nil.
If TEST is omitted or nil, `equal' is used."
  (let (found (tail alist) value)
    (while (and tail (not found))
      (let ((elt (car tail)))
	(when (funcall (or test 'equal) (if (consp elt) (car elt) elt) key)
	  (setq found t value (if (consp elt) (cdr elt) default))))
      (setq tail (cdr tail)))
    value))

(defun assoc-ignore-case (key alist)
  "Like `assoc', but ignores differences in case and text representation.
KEY must be a string.  Upper-case and lower-case letters are treated as equal.
Unibyte strings are converted to multibyte for comparison."
  (let (element)
    (while (and alist (not element))
      (if (eq t (compare-strings key 0 nil (car (car alist)) 0 nil t))
	  (setq element (car alist)))
      (setq alist (cdr alist)))
    element))

(defun assoc-ignore-representation (key alist)
  "Like `assoc', but ignores differences in text representation.
KEY must be a string.  
Unibyte strings are converted to multibyte for comparison."
  (let (element)
    (while (and alist (not element))
      (if (eq t (compare-strings key 0 nil (car (car alist)) 0 nil))
	  (setq element (car alist)))
      (setq alist (cdr alist)))
    element))

(defun member-ignore-case (elt list)
  "Like `member', but ignores differences in case and text representation.
ELT must be a string.  Upper-case and lower-case letters are treated as equal.
Unibyte strings are converted to multibyte for comparison."
  (while (and list (not (eq t (compare-strings elt 0 nil (car list) 0 nil t))))
    (setq list (cdr list)))
  list)

\f
;;;; Keymap support.

(defun undefined ()
  (interactive)
  (ding))

;Prevent the \{...} documentation construct
;from mentioning keys that run this command.
(put 'undefined 'suppress-keymap t)

(defun suppress-keymap (map &optional nodigits)
  "Make MAP override all normally self-inserting keys to be undefined.
Normally, as an exception, digits and minus-sign are set to make prefix args,
but optional second arg NODIGITS non-nil treats them like other chars."
  (substitute-key-definition 'self-insert-command 'undefined map global-map)
  (or nodigits
      (let (loop)
	(define-key map "-" 'negative-argument)
	;; Make plain numbers do numeric args.
	(setq loop ?0)
	(while (<= loop ?9)
	  (define-key map (char-to-string loop) 'digit-argument)
	  (setq loop (1+ loop))))))

;Moved to keymap.c
;(defun copy-keymap (keymap)
;  "Return a copy of KEYMAP"  
;  (while (not (keymapp keymap))
;    (setq keymap (signal 'wrong-type-argument (list 'keymapp keymap))))
;  (if (vectorp keymap)
;      (copy-sequence keymap)
;      (copy-alist keymap)))

(defvar key-substitution-in-progress nil
 "Used internally by substitute-key-definition.")

(defun substitute-key-definition (olddef newdef keymap &optional oldmap prefix)
  "Replace OLDDEF with NEWDEF for any keys in KEYMAP now defined as OLDDEF.
In other words, OLDDEF is replaced with NEWDEF where ever it appears.
Alternatively, if optional fourth argument OLDMAP is specified, we redefine
in KEYMAP as NEWDEF those keys which are defined as OLDDEF in OLDMAP."
  ;; Don't document PREFIX in the doc string because we don't want to
  ;; advertise it.  It's meant for recursive calls only.  Here's its
  ;; meaning
  
  ;; If optional argument PREFIX is specified, it should be a key
  ;; prefix, a string.  Redefined bindings will then be bound to the
  ;; original key, with PREFIX added at the front.
  (or prefix (setq prefix ""))
  (let* ((scan (or oldmap keymap))
	 (vec1 (vector nil))
	 (prefix1 (vconcat prefix vec1))
	 (key-substitution-in-progress
	  (cons scan key-substitution-in-progress)))
    ;; Scan OLDMAP, finding each char or event-symbol that
    ;; has any definition, and act on it with hack-key.
    (while (consp scan)
      (if (consp (car scan))
	  (let ((char (car (car scan)))
		(defn (cdr (car scan))))
	    ;; The inside of this let duplicates exactly
	    ;; the inside of the following let that handles array elements.
	    (aset vec1 0 char)
	    (aset prefix1 (length prefix) char)
	    (let (inner-def skipped)
	      ;; Skip past menu-prompt.
	      (while (stringp (car-safe defn))
		(setq skipped (cons (car defn) skipped))
		(setq defn (cdr defn)))
	      ;; Skip past cached key-equivalence data for menu items.
	      (and (consp defn) (consp (car defn))
		   (setq defn (cdr defn)))
	      (setq inner-def defn)
	      ;; Look past a symbol that names a keymap.
	      (while (and (symbolp inner-def)
			  (fboundp inner-def))
		(setq inner-def (symbol-function inner-def)))
	      (if (or (eq defn olddef)
		      ;; Compare with equal if definition is a key sequence.
		      ;; That is useful for operating on function-key-map.
		      (and (or (stringp defn) (vectorp defn))
			   (equal defn olddef)))
		  (define-key keymap prefix1 (nconc (nreverse skipped) newdef))
		(if (and (keymapp defn)
			 ;; Avoid recursively scanning
			 ;; where KEYMAP does not have a submap.
			 (let ((elt (lookup-key keymap prefix1)))
			   (or (null elt)
			       (keymapp elt)))
			 ;; Avoid recursively rescanning keymap being scanned.
			 (not (memq inner-def
				    key-substitution-in-progress)))
		    ;; If this one isn't being scanned already,
		    ;; scan it now.
		    (substitute-key-definition olddef newdef keymap
					       inner-def
					       prefix1)))))
	(if (vectorp (car scan))
	    (let* ((array (car scan))
		   (len (length array))
		   (i 0))
	      (while (< i len)
		(let ((char i) (defn (aref array i)))
		  ;; The inside of this let duplicates exactly
		  ;; the inside of the previous let.
		  (aset vec1 0 char)
		  (aset prefix1 (length prefix) char)
		  (let (inner-def skipped)
		    ;; Skip past menu-prompt.
		    (while (stringp (car-safe defn))
		      (setq skipped (cons (car defn) skipped))
		      (setq defn (cdr defn)))
		    (and (consp defn) (consp (car defn))
			 (setq defn (cdr defn)))
		    (setq inner-def defn)
		    (while (and (symbolp inner-def)
				(fboundp inner-def))
		      (setq inner-def (symbol-function inner-def)))
		    (if (or (eq defn olddef)
			    (and (or (stringp defn) (vectorp defn))
				 (equal defn olddef)))
			(define-key keymap prefix1
			  (nconc (nreverse skipped) newdef))
		      (if (and (keymapp defn)
			       (let ((elt (lookup-key keymap prefix1)))
				 (or (null elt)
				     (keymapp elt)))
			       (not (memq inner-def
					  key-substitution-in-progress)))
			  (substitute-key-definition olddef newdef keymap
						     inner-def
						     prefix1)))))
		(setq i (1+ i))))
	  (if (char-table-p (car scan))
	      (map-char-table
	       (function (lambda (char defn)
			   (let ()
			     ;; The inside of this let duplicates exactly
			     ;; the inside of the previous let,
			     ;; except that it uses set-char-table-range
			     ;; instead of define-key.
			     (aset vec1 0 char)
			     (aset prefix1 (length prefix) char)
			     (let (inner-def skipped)
			       ;; Skip past menu-prompt.
			       (while (stringp (car-safe defn))
				 (setq skipped (cons (car defn) skipped))
				 (setq defn (cdr defn)))
			       (and (consp defn) (consp (car defn))
				    (setq defn (cdr defn)))
			       (setq inner-def defn)
			       (while (and (symbolp inner-def)
					   (fboundp inner-def))
				 (setq inner-def (symbol-function inner-def)))
			       (if (or (eq defn olddef)
				       (and (or (stringp defn) (vectorp defn))
					    (equal defn olddef)))
				   (define-key keymap prefix1
				     (nconc (nreverse skipped) newdef))
				 (if (and (keymapp defn)
					  (let ((elt (lookup-key keymap prefix1)))
					    (or (null elt)
						(keymapp elt)))
					  (not (memq inner-def
						     key-substitution-in-progress)))
				     (substitute-key-definition olddef newdef keymap
								inner-def
								prefix1)))))))
	       (car scan)))))
      (setq scan (cdr scan)))))

(defun define-key-after (keymap key definition &optional after)
  "Add binding in KEYMAP for KEY => DEFINITION, right after AFTER's binding.
This is like `define-key' except that the binding for KEY is placed
just after the binding for the event AFTER, instead of at the beginning
of the map.  Note that AFTER must be an event type (like KEY), NOT a command
\(like DEFINITION).

If AFTER is t or omitted, the new binding goes at the end of the keymap.
AFTER should be a single event type--a symbol or a character, not a sequence.

Bindings are always added before any inherited map.

The order of bindings in a keymap matters when it is used as a menu."
  (unless after (setq after t))
  (or (keymapp keymap)
      (signal 'wrong-type-argument (list 'keymapp keymap)))
  (setq key
	(if (<= (length key) 1) (aref key 0)
	  (setq keymap (lookup-key keymap
				   (apply 'vector
					  (butlast (mapcar 'identity key)))))
	  (aref key (1- (length key)))))
  (let ((tail keymap) done inserted)
    (while (and (not done) tail)
      ;; Delete any earlier bindings for the same key.
      (if (eq (car-safe (car (cdr tail))) key)
	  (setcdr tail (cdr (cdr tail))))
      ;; If we hit an included map, go down that one.
      (if (keymapp (car tail)) (setq tail (car tail)))
      ;; When we reach AFTER's binding, insert the new binding after.
      ;; If we reach an inherited keymap, insert just before that.
      ;; If we reach the end of this keymap, insert at the end.
      (if (or (and (eq (car-safe (car tail)) after)
		   (not (eq after t)))
	      (eq (car (cdr tail)) 'keymap)
	      (null (cdr tail)))
	  (progn
	    ;; Stop the scan only if we find a parent keymap.
	    ;; Keep going past the inserted element
	    ;; so we can delete any duplications that come later.
	    (if (eq (car (cdr tail)) 'keymap)
		(setq done t))
	    ;; Don't insert more than once.
	    (or inserted
		(setcdr tail (cons (cons key definition) (cdr tail))))
	    (setq inserted t)))
      (setq tail (cdr tail)))))

(defmacro kbd (keys)
  "Convert KEYS to the internal Emacs key representation.
KEYS should be a string constant in the format used for
saving keyboard macros (see `insert-kbd-macro')."
  (read-kbd-macro keys))

(put 'keyboard-translate-table 'char-table-extra-slots 0)

(defun keyboard-translate (from to)
  "Translate character FROM to TO at a low level.
This function creates a `keyboard-translate-table' if necessary
and then modifies one entry in it."
  (or (char-table-p keyboard-translate-table)
      (setq keyboard-translate-table
	    (make-char-table 'keyboard-translate-table nil)))
  (aset keyboard-translate-table from to))

\f
;;;; The global keymap tree.  

;;; global-map, esc-map, and ctl-x-map have their values set up in
;;; keymap.c; we just give them docstrings here.

(defvar global-map nil
  "Default global keymap mapping Emacs keyboard input into commands.
The value is a keymap which is usually (but not necessarily) Emacs's
global map.")

(defvar esc-map nil
  "Default keymap for ESC (meta) commands.
The normal global definition of the character ESC indirects to this keymap.")

(defvar ctl-x-map nil
  "Default keymap for C-x commands.
The normal global definition of the character C-x indirects to this keymap.")

(defvar ctl-x-4-map (make-sparse-keymap)
  "Keymap for subcommands of C-x 4.")
(defalias 'ctl-x-4-prefix ctl-x-4-map)
(define-key ctl-x-map "4" 'ctl-x-4-prefix)

(defvar ctl-x-5-map (make-sparse-keymap)
  "Keymap for frame commands.")
(defalias 'ctl-x-5-prefix ctl-x-5-map)
(define-key ctl-x-map "5" 'ctl-x-5-prefix)

\f
;;;; Event manipulation functions.

;; The call to `read' is to ensure that the value is computed at load time
;; and not compiled into the .elc file.  The value is negative on most
;; machines, but not on all!
(defconst listify-key-sequence-1 (logior 128 (read "?\\M-\\^@")))

(defun listify-key-sequence (key)
  "Convert a key sequence to a list of events."
  (if (vectorp key)
      (append key nil)
    (mapcar (function (lambda (c)
			(if (> c 127)
			    (logxor c listify-key-sequence-1)
			  c)))
	    (append key nil))))

(defsubst eventp (obj)
  "True if the argument is an event object."
  (or (integerp obj)
      (and (symbolp obj)
	   (get obj 'event-symbol-elements))
      (and (consp obj)
	   (symbolp (car obj))
	   (get (car obj) 'event-symbol-elements))))

(defun event-modifiers (event)
  "Returns a list of symbols representing the modifier keys in event EVENT.
The elements of the list may include `meta', `control',
`shift', `hyper', `super', `alt', `click', `double', `triple', `drag',
and `down'."
  (let ((type event))
    (if (listp type)
	(setq type (car type)))
    (if (symbolp type)
	(cdr (get type 'event-symbol-elements))
      (let ((list nil))
	(or (zerop (logand type ?\M-\^@))
	    (setq list (cons 'meta list)))
	(or (and (zerop (logand type ?\C-\^@))
		 (>= (logand type 127) 32))
	    (setq list (cons 'control list)))
	(or (and (zerop (logand type ?\S-\^@))
		 (= (logand type 255) (downcase (logand type 255))))
	    (setq list (cons 'shift list)))
	(or (zerop (logand type ?\H-\^@))
	    (setq list (cons 'hyper list)))
	(or (zerop (logand type ?\s-\^@))
	    (setq list (cons 'super list)))
	(or (zerop (logand type ?\A-\^@))
	    (setq list (cons 'alt list)))
	list))))

(defun event-basic-type (event)
  "Returns the basic type of the given event (all modifiers removed).
The value is a printing character (not upper case) or a symbol."
  (if (consp event)
      (setq event (car event)))
  (if (symbolp event)
      (car (get event 'event-symbol-elements))
    (let ((base (logand event (1- (lsh 1 18)))))
      (downcase (if (< base 32) (logior base 64) base)))))

(defsubst mouse-movement-p (object)
  "Return non-nil if OBJECT is a mouse movement event."
  (and (consp object)
       (eq (car object) 'mouse-movement)))

(defsubst event-start (event)
  "Return the starting position of EVENT.
If EVENT is a mouse press or a mouse click, this returns the location
of the event.
If EVENT is a drag, this returns the drag's starting position.
The return value is of the form
   (WINDOW BUFFER-POSITION (X . Y) TIMESTAMP)
The `posn-' functions access elements of such lists."
  (nth 1 event))

(defsubst event-end (event)
  "Return the ending location of EVENT.  EVENT should be a click or drag event.
If EVENT is a click event, this function is the same as `event-start'.
The return value is of the form
   (WINDOW BUFFER-POSITION (X . Y) TIMESTAMP)
The `posn-' functions access elements of such lists."
  (nth (if (consp (nth 2 event)) 2 1) event))

(defsubst event-click-count (event)
  "Return the multi-click count of EVENT, a click or drag event.
The return value is a positive integer."
  (if (integerp (nth 2 event)) (nth 2 event) 1))

(defsubst posn-window (position)
  "Return the window in POSITION.
POSITION should be a list of the form
   (WINDOW BUFFER-POSITION (X . Y) TIMESTAMP)
as returned by the `event-start' and `event-end' functions."
  (nth 0 position))

(defsubst posn-point (position)
  "Return the buffer location in POSITION.
POSITION should be a list of the form
   (WINDOW BUFFER-POSITION (X . Y) TIMESTAMP)
as returned by the `event-start' and `event-end' functions."
  (if (consp (nth 1 position))
      (car (nth 1 position))
    (nth 1 position)))

(defsubst posn-x-y (position)
  "Return the x and y coordinates in POSITION.
POSITION should be a list of the form
   (WINDOW BUFFER-POSITION (X . Y) TIMESTAMP)
as returned by the `event-start' and `event-end' functions."
  (nth 2 position))

(defun posn-col-row (position)
  "Return the column and row in POSITION, measured in characters.
POSITION should be a list of the form
   (WINDOW BUFFER-POSITION (X . Y) TIMESTAMP)
as returned by the `event-start' and `event-end' functions.
For a scroll-bar event, the result column is 0, and the row
corresponds to the vertical position of the click in the scroll bar."
  (let ((pair   (nth 2 position))
	(window (posn-window position)))
    (if (eq (if (consp (nth 1 position))
		(car (nth 1 position))
	      (nth 1 position))
	    'vertical-scroll-bar)
	(cons 0 (scroll-bar-scale pair (1- (window-height window))))
      (if (eq (if (consp (nth 1 position))
		  (car (nth 1 position))
		(nth 1 position))
	      'horizontal-scroll-bar)
	  (cons (scroll-bar-scale pair (window-width window)) 0)
	(let* ((frame (if (framep window) window (window-frame window)))
	       (x (/ (car pair) (frame-char-width frame)))
	       (y (/ (cdr pair) (frame-char-height frame))))
	  (cons x y))))))

(defsubst posn-timestamp (position)
  "Return the timestamp of POSITION.
POSITION should be a list of the form
   (WINDOW BUFFER-POSITION (X . Y) TIMESTAMP)
as returned by the `event-start' and `event-end' functions."
  (nth 3 position))

\f
;;;; Obsolescent names for functions.

(defalias 'dot 'point)
(defalias 'dot-marker 'point-marker)
(defalias 'dot-min 'point-min)
(defalias 'dot-max 'point-max)
(defalias 'window-dot 'window-point)
(defalias 'set-window-dot 'set-window-point)
(defalias 'read-input 'read-string)
(defalias 'send-string 'process-send-string)
(defalias 'send-region 'process-send-region)
(defalias 'show-buffer 'set-window-buffer)
(defalias 'buffer-flush-undo 'buffer-disable-undo)
(defalias 'eval-current-buffer 'eval-buffer)
(defalias 'compiled-function-p 'byte-code-function-p)
(defalias 'define-function 'defalias)

(defalias 'sref 'aref)
(make-obsolete 'sref 'aref "20.4")
(make-obsolete 'char-bytes "Now this function always returns 1" "20.4")

(defun insert-string (&rest args)
  "Mocklisp-compatibility insert function.
Like the function `insert' except that any argument that is a number
is converted into a string by expressing it in decimal."
  (dolist (el args)
    (insert (if (integerp el) (number-to-string el) el))))

(make-obsolete 'insert-string 'insert "21.3")

;; Some programs still use this as a function.
(defun baud-rate ()
  "Obsolete function returning the value of the `baud-rate' variable.
Please convert your programs to use the variable `baud-rate' directly."
  baud-rate)

(defalias 'focus-frame 'ignore)
(defalias 'unfocus-frame 'ignore)
\f
;;;; Alternate names for functions - these are not being phased out.

(defalias 'string= 'string-equal)
(defalias 'string< 'string-lessp)
(defalias 'move-marker 'set-marker)
(defalias 'rplaca 'setcar)
(defalias 'rplacd 'setcdr)
(defalias 'beep 'ding) ;preserve lingual purity
(defalias 'indent-to-column 'indent-to)
(defalias 'backward-delete-char 'delete-backward-char)
(defalias 'search-forward-regexp (symbol-function 're-search-forward))
(defalias 'search-backward-regexp (symbol-function 're-search-backward))
(defalias 'int-to-string 'number-to-string)
(defalias 'store-match-data 'set-match-data)
;; These are the XEmacs names:
(defalias 'point-at-eol 'line-end-position)
(defalias 'point-at-bol 'line-beginning-position)

;;; Should this be an obsolete name?  If you decide it should, you get
;;; to go through all the sources and change them.
(defalias 'string-to-int 'string-to-number)
\f
;;;; Hook manipulation functions.

(defun make-local-hook (hook)
  "Make the hook HOOK local to the current buffer.
The return value is HOOK.

You never need to call this function now that `add-hook' does it for you
if its LOCAL argument is non-nil.

When a hook is local, its local and global values
work in concert: running the hook actually runs all the hook
functions listed in *either* the local value *or* the global value
of the hook variable.

This function works by making t a member of the buffer-local value,
which acts as a flag to run the hook functions in the default value as
well.  This works for all normal hooks, but does not work for most
non-normal hooks yet.  We will be changing the callers of non-normal
hooks so that they can handle localness; this has to be done one by
one.

This function does nothing if HOOK is already local in the current
buffer.

Do not use `make-local-variable' to make a hook variable buffer-local."
  (if (local-variable-p hook)
      nil
    (or (boundp hook) (set hook nil))
    (make-local-variable hook)
    (set hook (list t)))
  hook)
(make-obsolete 'make-local-hook "Not necessary any more." "21.1")

(defun add-hook (hook function &optional append local)
  "Add to the value of HOOK the function FUNCTION.
FUNCTION is not added if already present.
FUNCTION is added (if necessary) at the beginning of the hook list
unless the optional argument APPEND is non-nil, in which case
FUNCTION is added at the end.

The optional fourth argument, LOCAL, if non-nil, says to modify
the hook's buffer-local value rather than its default value.
This makes the hook buffer-local if needed, and it makes t a member
of the buffer-local value.  That acts as a flag to run the hook
functions in the default value as well as in the local value.

HOOK should be a symbol, and FUNCTION may be any valid function.  If
HOOK is void, it is first set to nil.  If HOOK's value is a single
function, it is changed to a list of functions."
  (or (boundp hook) (set hook nil))
  (or (default-boundp hook) (set-default hook nil))
  (if local (unless (local-variable-if-set-p hook)
	      (set (make-local-variable hook) (list t)))
    ;; Detect the case where make-local-variable was used on a hook
    ;; and do what we used to do.
    (unless (and (consp (symbol-value hook)) (memq t (symbol-value hook)))
      (setq local t)))
  (let ((hook-value (if local (symbol-value hook) (default-value hook))))
    ;; If the hook value is a single function, turn it into a list.
    (when (or (not (listp hook-value)) (eq (car hook-value) 'lambda))
      (setq hook-value (list hook-value)))
    ;; Do the actual addition if necessary
    (unless (member function hook-value)
      (setq hook-value
	    (if append
		(append hook-value (list function))
	      (cons function hook-value))))
    ;; Set the actual variable
    (if local (set hook hook-value) (set-default hook hook-value))))

(defun remove-hook (hook function &optional local)
  "Remove from the value of HOOK the function FUNCTION.
HOOK should be a symbol, and FUNCTION may be any valid function.  If
FUNCTION isn't the value of HOOK, or, if FUNCTION doesn't appear in the
list of hooks to run in HOOK, then nothing is done.  See `add-hook'.

The optional third argument, LOCAL, if non-nil, says to modify
the hook's buffer-local value rather than its default value.
This makes the hook buffer-local if needed."
  (or (boundp hook) (set hook nil))
  (or (default-boundp hook) (set-default hook nil))
  (if local (unless (local-variable-if-set-p hook)
	      (set (make-local-variable hook) (list t)))
    ;; Detect the case where make-local-variable was used on a hook
    ;; and do what we used to do.
    (unless (and (consp (symbol-value hook)) (memq t (symbol-value hook)))
      (setq local t)))
  (let ((hook-value (if local (symbol-value hook) (default-value hook))))
    ;; Remove the function, for both the list and the non-list cases.
    (if (or (not (listp hook-value)) (eq (car hook-value) 'lambda))
	(if (equal hook-value function) (setq hook-value nil))
      (setq hook-value (delete function (copy-sequence hook-value))))
    ;; If the function is on the global hook, we need to shadow it locally
    ;;(when (and local (member function (default-value hook))
    ;;	       (not (member (cons 'not function) hook-value)))
    ;;  (push (cons 'not function) hook-value))
    ;; Set the actual variable
    (if local (set hook hook-value) (set-default hook hook-value))))

(defun add-to-list (list-var element &optional append)
  "Add to the value of LIST-VAR the element ELEMENT if it isn't there yet.
The test for presence of ELEMENT is done with `equal'.
If ELEMENT is added, it is added at the beginning of the list,
unless the optional argument APPEND is non-nil, in which case
ELEMENT is added at the end.

The return value is the new value of LIST-VAR.

If you want to use `add-to-list' on a variable that is not defined
until a certain package is loaded, you should put the call to `add-to-list'
into a hook function that will be run only after loading the package.
`eval-after-load' provides one way to do this.  In some cases
other hooks, such as major mode hooks, can do the job."
  (if (member element (symbol-value list-var))
      (symbol-value list-var)
    (set list-var
	 (if append
	     (append (symbol-value list-var) (list element))
	   (cons element (symbol-value list-var))))))

\f
;;; Load history

(defvar symbol-file-load-history-loaded nil
  "Non-nil means we have loaded the file `fns-VERSION.el' in `exec-directory'.
That file records the part of `load-history' for preloaded files,
which is cleared out before dumping to make Emacs smaller.")

(defun load-symbol-file-load-history ()
  "Load the file `fns-VERSION.el' in `exec-directory' if not already done.
That file records the part of `load-history' for preloaded files,
which is cleared out before dumping to make Emacs smaller."
  (unless symbol-file-load-history-loaded
    (load (expand-file-name
	   ;; fns-XX.YY.ZZ.el does not work on DOS filesystem.
	   (if (eq system-type 'ms-dos)
	       "fns.el"
	     (format "fns-%s.el" emacs-version))
	   exec-directory)
	  ;; The file name fns-%s.el already has a .el extension.
	  nil nil t)
    (setq symbol-file-load-history-loaded t)))

(defun symbol-file (function)
  "Return the input source from which FUNCTION was loaded.
The value is normally a string that was passed to `load':
either an absolute file name, or a library name
\(with no directory name and no `.el' or `.elc' at the end).
It can also be nil, if the definition is not associated with any file."
  (load-symbol-file-load-history)
  (let ((files load-history)
	file functions)
    (while files
      (if (memq function (cdr (car files)))
	  (setq file (car (car files)) files nil))
      (setq files (cdr files)))
    file))

\f
;;;; Specifying things to do after certain files are loaded.

(defun eval-after-load (file form)
  "Arrange that, if FILE is ever loaded, FORM will be run at that time.
This makes or adds to an entry on `after-load-alist'.
If FILE is already loaded, evaluate FORM right now.
It does nothing if FORM is already on the list for FILE.
FILE must match exactly.  Normally FILE is the name of a library,
with no directory or extension specified, since that is how `load'
is normally called.
FILE can also be a feature (i.e. a symbol), in which case FORM is
evaluated whenever that feature is `provide'd."
  (let ((elt (assoc file after-load-alist)))
    ;; Make sure there is an element for FILE.
    (unless elt (setq elt (list file)) (push elt after-load-alist))
    ;; Add FORM to the element if it isn't there.
    (unless (member form (cdr elt))
      (nconc elt (list form))
      ;; If the file has been loaded already, run FORM right away.
      (if (if (symbolp file)
	      (featurep file)
	    ;; Make sure `load-history' contains the files dumped with
	    ;; Emacs for the case that FILE is one of them.
	    (load-symbol-file-load-history)
	    (assoc file load-history))
	  (eval form))))
  form)

(defun eval-next-after-load (file)
  "Read the following input sexp, and run it whenever FILE is loaded.
This makes or adds to an entry on `after-load-alist'.
FILE should be the name of a library, with no directory name."
  (eval-after-load file (read)))

\f
;;;; Input and display facilities.

(defvar read-quoted-char-radix 8
  "*Radix for \\[quoted-insert] and other uses of `read-quoted-char'.
Legitimate radix values are 8, 10 and 16.")

(custom-declare-variable-early
 'read-quoted-char-radix 8 
 "*Radix for \\[quoted-insert] and other uses of `read-quoted-char'.
Legitimate radix values are 8, 10 and 16."
  :type '(choice (const 8) (const 10) (const 16))
  :group 'editing-basics)

(defun read-quoted-char (&optional prompt)
  "Like `read-char', but do not allow quitting.
Also, if the first character read is an octal digit,
we read any number of octal digits and return the
specified character code.  Any nondigit terminates the sequence.
If the terminator is RET, it is discarded;
any other terminator is used itself as input.

The optional argument PROMPT specifies a string to use to prompt the user.
The variable `read-quoted-char-radix' controls which radix to use
for numeric input."
  (let ((message-log-max nil) done (first t) (code 0) char)
    (while (not done)
      (let ((inhibit-quit first)
	    ;; Don't let C-h get the help message--only help function keys.
	    (help-char nil)
	    (help-form
	     "Type the special character you want to use,
or the octal character code.
RET terminates the character code and is discarded;
any other non-digit terminates the character code and is then used as input."))
	(setq char (read-event (and prompt (format "%s-" prompt)) t))
	(if inhibit-quit (setq quit-flag nil)))
      ;; Translate TAB key into control-I ASCII character, and so on.
      (and char
	   (let ((translated (lookup-key function-key-map (vector char))))
	     (if (arrayp translated)
		 (setq char (aref translated 0)))))
      (cond ((null char))
	    ((not (integerp char))
	     (setq unread-command-events (list char)
		   done t))
	    ((/= (logand char ?\M-\^@) 0)
	     ;; Turn a meta-character into a character with the 0200 bit set.
	     (setq code (logior (logand char (lognot ?\M-\^@)) 128)
		   done t))
	    ((and (<= ?0 char) (< char (+ ?0 (min 10 read-quoted-char-radix))))
	     (setq code (+ (* code read-quoted-char-radix) (- char ?0)))
	     (and prompt (setq prompt (message "%s %c" prompt char))))
	    ((and (<= ?a (downcase char))
		  (< (downcase char) (+ ?a -10 (min 26 read-quoted-char-radix))))
	     (setq code (+ (* code read-quoted-char-radix)
			   (+ 10 (- (downcase char) ?a))))
	     (and prompt (setq prompt (message "%s %c" prompt char))))
	    ((and (not first) (eq char ?\C-m))
	     (setq done t))
	    ((not first)
	     (setq unread-command-events (list char)
		   done t))
	    (t (setq code char
		     done t)))
      (setq first nil))
    code))

(defun read-passwd (prompt &optional confirm default)
  "Read a password, prompting with PROMPT.  Echo `.' for each character typed.
End with RET, LFD, or ESC.  DEL or C-h rubs out.  C-u kills line.
Optional argument CONFIRM, if non-nil, then read it twice to make sure.
Optional DEFAULT is a default password to use instead of empty input."
  (if confirm
      (let (success)
	(while (not success)
	  (let ((first (read-passwd prompt nil default))
		(second (read-passwd "Confirm password: " nil default)))
	    (if (equal first second)
		(progn
		  (and (arrayp second) (fillarray second ?\0))
		  (setq success first))
	      (and (arrayp first) (fillarray first ?\0))
	      (and (arrayp second) (fillarray second ?\0))
	      (message "Password not repeated accurately; please start over")
	      (sit-for 1))))
	success)
    (let ((pass nil)
	  (c 0)
	  (echo-keystrokes 0)
	  (cursor-in-echo-area t))
      (while (progn (message "%s%s"
			     prompt
			     (make-string (length pass) ?.))
		    (setq c (read-char-exclusive nil t))
		    (and (/= c ?\r) (/= c ?\n) (/= c ?\e)))
	(clear-this-command-keys)
	(if (= c ?\C-u)
	    (progn
	      (and (arrayp pass) (fillarray pass ?\0))
	      (setq pass ""))
	  (if (and (/= c ?\b) (/= c ?\177))
	      (let* ((new-char (char-to-string c))
		     (new-pass (concat pass new-char)))
		(and (arrayp pass) (fillarray pass ?\0))
		(fillarray new-char ?\0)
		(setq c ?\0)
		(setq pass new-pass))
	    (if (> (length pass) 0)
		(let ((new-pass (substring pass 0 -1)))
		  (and (arrayp pass) (fillarray pass ?\0))
		  (setq pass new-pass))))))
      (message nil)
      (or pass default ""))))
\f
(defmacro atomic-change-group (&rest body)
  "Perform BODY as an atomic change group.
This means that if BODY exits abnormally,
all of its changes to the current buffer are undone.
This works regadless of whether undo is enabled in the buffer.

This mechanism is transparent to ordinary use of undo;
if undo is enabled in the buffer and BODY succeeds, the
user can undo the change normally."
  (let ((handle (make-symbol "--change-group-handle--"))
	(success (make-symbol "--change-group-success--")))
    `(let ((,handle (prepare-change-group))
	   (,success nil))
       (unwind-protect
	   (progn
	     ;; This is inside the unwind-protect because
	     ;; it enables undo if that was disabled; we need
	     ;; to make sure that it gets disabled again.
	     (activate-change-group ,handle)
	     ,@body
	     (setq ,success t))
	 ;; Either of these functions will disable undo
	 ;; if it was disabled before.
	 (if ,success
	     (accept-change-group ,handle)
	   (cancel-change-group ,handle))))))

(defun prepare-change-group (&optional buffer)
  "Return a handle for the current buffer's state, for a change group.
If you specify BUFFER, make a handle for BUFFER's state instead.

Pass the handle to `activate-change-group' afterward to initiate
the actual changes of the change group.

To finish the change group, call either `accept-change-group' or
`cancel-change-group' passing the same handle as argument.  Call
`accept-change-group' to accept the changes in the group as final;
call `cancel-change-group' to undo them all.  You should use
`unwind-protect' to make sure the group is always finished.  The call
to `activate-change-group' should be inside the `unwind-protect'.
Once you finish the group, don't use the handle again--don't try to
finish the same group twice.  For a simple example of correct use, see
the source code of `atomic-change-group'.

The handle records only the specified buffer.  To make a multibuffer
change group, call this function once for each buffer you want to
cover, then use `nconc' to combine the returned values, like this:

  (nconc (prepare-change-group buffer-1)
         (prepare-change-group buffer-2))

You can then activate that multibuffer change group with a single
call to `activate-change-group' and finish it with a single call
to `accept-change-group' or `cancel-change-group'."

  (list (cons (current-buffer) buffer-undo-list)))

(defun activate-change-group (handle)
  "Activate a change group made with `prepare-change-group' (which see)."
  (dolist (elt handle)
    (with-current-buffer (car elt)
      (if (eq buffer-undo-list t)
	  (setq buffer-undo-list nil)))))

(defun accept-change-group (handle)
  "Finish a change group made with `prepare-change-group' (which see).
This finishes the change group by accepting its changes as final."
  (dolist (elt handle)
    (with-current-buffer (car elt)
      (if (eq elt t)
	  (setq buffer-undo-list t)))))

(defun cancel-change-group (handle)
  "Finish a change group made with `prepare-change-group' (which see).
This finishes the change group by reverting all of its changes."
  (dolist (elt handle)
    (with-current-buffer (car elt)
      (setq elt (cdr elt))
      (let ((old-car 
	     (if (consp elt) (car elt)))
	    (old-cdr
	     (if (consp elt) (cdr elt))))
	;; Temporarily truncate the undo log at ELT.
	(when (consp elt)
	  (setcar elt nil) (setcdr elt nil))
	(unless (eq last-command 'undo) (undo-start))
	;; Make sure there's no confusion.
	(when (and (consp elt) (not (eq elt (last pending-undo-list))))
	  (error "Undoing to some unrelated state"))
	;; Undo it all.
	(while pending-undo-list (undo-more 1))
	;; Reset the modified cons cell ELT to its original content.
	(when (consp elt)
	  (setcar elt old-car)
	  (setcdr elt old-cdr))
	;; Revert the undo info to what it was when we grabbed the state.
	(setq buffer-undo-list elt)))))
\f
(defun force-mode-line-update (&optional all)
  "Force the mode line of the current buffer to be redisplayed.
With optional non-nil ALL, force redisplay of all mode lines."
  (if all (save-excursion (set-buffer (other-buffer))))
  (set-buffer-modified-p (buffer-modified-p)))

(defun momentary-string-display (string pos &optional exit-char message)
  "Momentarily display STRING in the buffer at POS.
Display remains until next character is typed.
If the char is EXIT-CHAR (optional third arg, default is SPC) it is swallowed;
otherwise it is then available as input (as a command if nothing else).
Display MESSAGE (optional fourth arg) in the echo area.
If MESSAGE is nil, instructions to type EXIT-CHAR are displayed there."
  (or exit-char (setq exit-char ?\ ))
  (let ((inhibit-read-only t)
	;; Don't modify the undo list at all.
	(buffer-undo-list t)
	(modified (buffer-modified-p))
	(name buffer-file-name)
	insert-end)
    (unwind-protect
	(progn
	  (save-excursion
	    (goto-char pos)
	    ;; defeat file locking... don't try this at home, kids!
	    (setq buffer-file-name nil)
	    (insert-before-markers string)
	    (setq insert-end (point))
	    ;; If the message end is off screen, recenter now.
	    (if (< (window-end nil t) insert-end)
		(recenter (/ (window-height) 2)))
	    ;; If that pushed message start off the screen,
	    ;; scroll to start it at the top of the screen.
	    (move-to-window-line 0)
	    (if (> (point) pos)
		(progn
		  (goto-char pos)
		  (recenter 0))))
	  (message (or message "Type %s to continue editing.")
		   (single-key-description exit-char))
	  (let ((char (read-event)))
	    (or (eq char exit-char)
		(setq unread-command-events (list char)))))
      (if insert-end
	  (save-excursion
	    (delete-region pos insert-end)))
      (setq buffer-file-name name)
      (set-buffer-modified-p modified))))

\f
;;;; Overlay operations

(defun copy-overlay (o)
  "Return a copy of overlay O."
  (let ((o1 (make-overlay (overlay-start o) (overlay-end o)
			  ;; FIXME: there's no easy way to find the
			  ;; insertion-type of the two markers.
			  (overlay-buffer o)))
	(props (overlay-properties o)))
    (while props
      (overlay-put o1 (pop props) (pop props)))
    o1))

(defun remove-overlays (beg end name val)
  "Clear BEG and END of overlays whose property NAME has value VAL.
Overlays might be moved and or split."
  (if (< end beg)
      (setq beg (prog1 end (setq end beg))))
  (save-excursion
    (dolist (o (overlays-in beg end))
      (when (eq (overlay-get o name) val)
	;; Either push this overlay outside beg...end
	;; or split it to exclude beg...end
	;; or delete it entirely (if it is contained in beg...end).
	(if (< (overlay-start o) beg)
	    (if (> (overlay-end o) end)
		(progn
		  (move-overlay (copy-overlay o)
				(overlay-start o) beg)
		  (move-overlay o end (overlay-end o)))
	      (move-overlay o (overlay-start o) beg))
	  (if (> (overlay-end o) end)
	      (move-overlay o end (overlay-end o))
	    (delete-overlay o)))))))
\f
;;;; Miscellanea.

;; A number of major modes set this locally.
;; Give it a global value to avoid compiler warnings.
(defvar font-lock-defaults nil)

(defvar suspend-hook nil
  "Normal hook run by `suspend-emacs', before suspending.")

(defvar suspend-resume-hook nil
  "Normal hook run by `suspend-emacs', after Emacs is continued.")

(defvar temp-buffer-show-hook nil
  "Normal hook run by `with-output-to-temp-buffer' after displaying the buffer.
When the hook runs, the temporary buffer is current, and the window it
was displayed in is selected.  This hook is normally set up with a
function to make the buffer read only, and find function names and
variable names in it, provided the major mode is still Help mode.")

(defvar temp-buffer-setup-hook nil
  "Normal hook run by `with-output-to-temp-buffer' at the start.
When the hook runs, the temporary buffer is current.
This hook is normally set up with a function to put the buffer in Help
mode.")

;; Avoid compiler warnings about this variable,
;; which has a special meaning on certain system types.
(defvar buffer-file-type nil
  "Non-nil if the visited file is a binary file.
This variable is meaningful on MS-DOG and Windows NT.
On those systems, it is automatically local in every buffer.
On other systems, this variable is normally always nil.")

;; This should probably be written in C (i.e., without using `walk-windows').
(defun get-buffer-window-list (buffer &optional minibuf frame)
  "Return windows currently displaying BUFFER, or nil if none.
See `walk-windows' for the meaning of MINIBUF and FRAME."
  (let ((buffer (if (bufferp buffer) buffer (get-buffer buffer))) windows)
    (walk-windows (function (lambda (window)
			      (if (eq (window-buffer window) buffer)
				  (setq windows (cons window windows)))))
		  minibuf frame)
    windows))

(defun ignore (&rest ignore)
  "Do nothing and return nil.
This function accepts any number of arguments, but ignores them."
  (interactive)
  nil)

(defun error (&rest args)
  "Signal an error, making error message by passing all args to `format'.
In Emacs, the convention is that error messages start with a capital
letter but *do not* end with a period.  Please follow this convention
for the sake of consistency."
  (while t
    (signal 'error (list (apply 'format args)))))

(defalias 'user-original-login-name 'user-login-name)

(defun start-process-shell-command (name buffer &rest args)
  "Start a program in a subprocess.  Return the process object for it.
Args are NAME BUFFER COMMAND &rest COMMAND-ARGS.
NAME is name for process.  It is modified if necessary to make it unique.
BUFFER is the buffer or (buffer-name) to associate with the process.
 Process output goes at end of that buffer, unless you specify
 an output stream or filter function to handle the output.
 BUFFER may be also nil, meaning that this process is not associated
 with any buffer
Third arg is command name, the name of a shell command.
Remaining arguments are the arguments for the command.
Wildcards and redirection are handled as usual in the shell."
  (cond
   ((eq system-type 'vax-vms)
    (apply 'start-process name buffer args))
   ;; We used to use `exec' to replace the shell with the command,
   ;; but that failed to handle (...) and semicolon, etc.
   (t
    (start-process name buffer shell-file-name shell-command-switch
		   (mapconcat 'identity args " ")))))

(defun call-process-shell-command (command &optional infile buffer display
					   &rest args)
  "Execute the shell command COMMAND synchronously in separate process.
The remaining arguments are optional.
The program's input comes from file INFILE (nil means `/dev/null').
Insert output in BUFFER before point; t means current buffer;
 nil for BUFFER means discard it; 0 means discard and don't wait.
BUFFER can also have the form (REAL-BUFFER STDERR-FILE); in that case,
REAL-BUFFER says what to do with standard output, as above,
while STDERR-FILE says what to do with standard error in the child.
STDERR-FILE may be nil (discard standard error output),
t (mix it with ordinary output), or a file name string.

Fourth arg DISPLAY non-nil means redisplay buffer as output is inserted.
Remaining arguments are strings passed as additional arguments for COMMAND.
Wildcards and redirection are handled as usual in the shell.

If BUFFER is 0, `call-process-shell-command' returns immediately with value nil.
Otherwise it waits for COMMAND to terminate and returns a numeric exit
status or a signal description string.
If you quit, the process is killed with SIGINT, or SIGKILL if you quit again."
  (cond
   ((eq system-type 'vax-vms)
    (apply 'call-process command infile buffer display args))
   ;; We used to use `exec' to replace the shell with the command,
   ;; but that failed to handle (...) and semicolon, etc.
   (t
    (call-process shell-file-name
		  infile buffer display
		  shell-command-switch
		  (mapconcat 'identity (cons command args) " ")))))
\f
(defmacro with-current-buffer (buffer &rest body)
  "Execute the forms in BODY with BUFFER as the current buffer.
The value returned is the value of the last form in BODY.
See also `with-temp-buffer'."
  (cons 'save-current-buffer
	(cons (list 'set-buffer buffer)
	      body)))

(defmacro with-temp-file (file &rest body)
  "Create a new buffer, evaluate BODY there, and write the buffer to FILE.
The value returned is the value of the last form in BODY.
See also `with-temp-buffer'."
  (let ((temp-file (make-symbol "temp-file"))
	(temp-buffer (make-symbol "temp-buffer")))
    `(let ((,temp-file ,file)
	   (,temp-buffer
	    (get-buffer-create (generate-new-buffer-name " *temp file*"))))
       (unwind-protect
	   (prog1
	       (with-current-buffer ,temp-buffer
		 ,@body)
	     (with-current-buffer ,temp-buffer
	       (widen)
	       (write-region (point-min) (point-max) ,temp-file nil 0)))
	 (and (buffer-name ,temp-buffer)
	      (kill-buffer ,temp-buffer))))))

(defmacro with-temp-message (message &rest body)
  "Display MESSAGE temporarily if non-nil while BODY is evaluated.
The original message is restored to the echo area after BODY has finished.
The value returned is the value of the last form in BODY.
MESSAGE is written to the message log buffer if `message-log-max' is non-nil.
If MESSAGE is nil, the echo area and message log buffer are unchanged.
Use a MESSAGE of \"\" to temporarily clear the echo area."
  (let ((current-message (make-symbol "current-message"))
	(temp-message (make-symbol "with-temp-message")))
    `(let ((,temp-message ,message)
	   (,current-message))
       (unwind-protect
	   (progn
	     (when ,temp-message
	       (setq ,current-message (current-message))
	       (message "%s" ,temp-message))
	     ,@body)
	 (and ,temp-message
	      (if ,current-message
		  (message "%s" ,current-message)
		(message nil)))))))

(defmacro with-temp-buffer (&rest body)
  "Create a temporary buffer, and evaluate BODY there like `progn'.
See also `with-temp-file' and `with-output-to-string'."
  (let ((temp-buffer (make-symbol "temp-buffer")))
    `(let ((,temp-buffer
	    (get-buffer-create (generate-new-buffer-name " *temp*"))))
       (unwind-protect
	   (with-current-buffer ,temp-buffer
	     ,@body)
	 (and (buffer-name ,temp-buffer)
	      (kill-buffer ,temp-buffer))))))

(defmacro with-output-to-string (&rest body)
  "Execute BODY, return the text it sent to `standard-output', as a string."
  `(let ((standard-output
	  (get-buffer-create (generate-new-buffer-name " *string-output*"))))
     (let ((standard-output standard-output))
       ,@body)
     (with-current-buffer standard-output
       (prog1
	   (buffer-string)
	 (kill-buffer nil)))))

(defmacro with-local-quit (&rest body)
  "Execute BODY with `inhibit-quit' temporarily bound to nil."
  `(condition-case nil
       (let ((inhibit-quit nil))
	 ,@body)
     (quit (setq quit-flag t))))

(defmacro combine-after-change-calls (&rest body)
  "Execute BODY, but don't call the after-change functions till the end.
If BODY makes changes in the buffer, they are recorded
and the functions on `after-change-functions' are called several times
when BODY is finished.
The return value is the value of the last form in BODY.

If `before-change-functions' is non-nil, then calls to the after-change
functions can't be deferred, so in that case this macro has no effect.

Do not alter `after-change-functions' or `before-change-functions'
in BODY."
  `(unwind-protect
       (let ((combine-after-change-calls t))
	 . ,body)
     (combine-after-change-execute)))


(defvar delay-mode-hooks nil
  "If non-nil, `run-mode-hooks' should delay running the hooks.")
(defvar delayed-mode-hooks nil
  "List of delayed mode hooks waiting to be run.")
(make-variable-buffer-local 'delayed-mode-hooks)

(defun run-mode-hooks (&rest hooks)
  "Run mode hooks `delayed-mode-hooks' and HOOKS, or delay HOOKS.
Execution is delayed if `delay-mode-hooks' is non-nil.
Major mode functions should use this."
  (if delay-mode-hooks
      ;; Delaying case.
      (dolist (hook hooks)
	(push hook delayed-mode-hooks))
    ;; Normal case, just run the hook as before plus any delayed hooks.
    (setq hooks (nconc (nreverse delayed-mode-hooks) hooks))
    (setq delayed-mode-hooks nil)
    (apply 'run-hooks hooks)))

(defmacro delay-mode-hooks (&rest body)
  "Execute BODY, but delay any `run-mode-hooks'.
Only affects hooks run in the current buffer."
  `(progn
     (make-local-variable 'delay-mode-hooks)
     (let ((delay-mode-hooks t))
       ,@body)))

;; PUBLIC: find if the current mode derives from another.

(defun derived-mode-p (&rest modes)
  "Non-nil if the current major mode is derived from one of MODES.
Uses the `derived-mode-parent' property of the symbol to trace backwards."
  (let ((parent major-mode))
    (while (and (not (memq parent modes))
		(setq parent (get parent 'derived-mode-parent))))
    parent))

(defmacro with-syntax-table (table &rest body)
  "Evaluate BODY with syntax table of current buffer set to a copy of TABLE.
The syntax table of the current buffer is saved, BODY is evaluated, and the
saved table is restored, even in case of an abnormal exit.
Value is what BODY returns."
  (let ((old-table (make-symbol "table"))
	(old-buffer (make-symbol "buffer")))
    `(let ((,old-table (syntax-table))
	   (,old-buffer (current-buffer)))
       (unwind-protect
	   (progn
	     (set-syntax-table (copy-syntax-table ,table))
	     ,@body)
	 (save-current-buffer
	   (set-buffer ,old-buffer)
	   (set-syntax-table ,old-table))))))
\f
(defvar save-match-data-internal)

;; We use save-match-data-internal as the local variable because
;; that works ok in practice (people should not use that variable elsewhere).
;; We used to use an uninterned symbol; the compiler handles that properly
;; now, but it generates slower code.
(defmacro save-match-data (&rest body)
  "Execute the BODY forms, restoring the global value of the match data.
The value returned is the value of the last form in BODY."
  ;; It is better not to use backquote here,
  ;; because that makes a bootstrapping problem
  ;; if you need to recompile all the Lisp files using interpreted code.
  (list 'let
	'((save-match-data-internal (match-data)))
	(list 'unwind-protect
	      (cons 'progn body)
	      '(set-match-data save-match-data-internal))))

(defun substring-no-properties (string &optional from to)
  "Return a substring of STRING, with no text properties.
The substring starts at index FROM and ends before TO.
If FROM is nil or omitted, it defaults to the beginning of STRING.
If TO is nil or omitted, it defaults to the end of STRING.
If FROM or TO is negative, it counts from the end.

Simply (substring-no-properties STRING) copies a string without
its properties."
  (let ((str (substring string (or from 0) to)))
    (set-text-properties 0 (length str) nil str)
    str))

(defun match-string (num &optional string)
  "Return string of text matched by last search.
NUM specifies which parenthesized expression in the last regexp.
 Value is nil if NUMth pair didn't match, or there were less than NUM pairs.
Zero means the entire text matched by the whole regexp or whole string.
STRING should be given if the last search was by `string-match' on STRING."
  (if (match-beginning num)
      (if string
	  (substring string (match-beginning num) (match-end num))
	(buffer-substring (match-beginning num) (match-end num)))))

(defun match-string-no-properties (num &optional string)
  "Return string of text matched by last search, without text properties.
NUM specifies which parenthesized expression in the last regexp.
 Value is nil if NUMth pair didn't match, or there were less than NUM pairs.
Zero means the entire text matched by the whole regexp or whole string.
STRING should be given if the last search was by `string-match' on STRING."
  (if (match-beginning num)
      (if string
	  (let ((result
		 (substring string (match-beginning num) (match-end num))))
	    (set-text-properties 0 (length result) nil result)
	    result)
	(buffer-substring-no-properties (match-beginning num)
					(match-end num)))))

(defun split-string (string &optional separators)
  "Splits STRING into substrings where there are matches for SEPARATORS.
Each match for SEPARATORS is a splitting point.
The substrings between the splitting points are made into a list
which is returned.
If SEPARATORS is absent, it defaults to \"[ \\f\\t\\n\\r\\v]+\".

If there is match for SEPARATORS at the beginning of STRING, we do not
include a null substring for that.  Likewise, if there is a match
at the end of STRING, we don't include a null substring for that.

Modifies the match data; use `save-match-data' if necessary."
  (let ((rexp (or separators "[ \f\t\n\r\v]+"))
	(start 0)
	notfirst
	(list nil))
    (while (and (string-match rexp string
			      (if (and notfirst
				       (= start (match-beginning 0))
				       (< start (length string)))
				  (1+ start) start))
		(< (match-beginning 0) (length string)))
      (setq notfirst t)
      (or (eq (match-beginning 0) 0)
	  (and (eq (match-beginning 0) (match-end 0))
	       (eq (match-beginning 0) start))
	  (setq list
		(cons (substring string start (match-beginning 0))
		      list)))
      (setq start (match-end 0)))
    (or (eq start (length string))
	(setq list
	      (cons (substring string start)
		    list)))
    (nreverse list)))

(defun subst-char-in-string (fromchar tochar string &optional inplace)
  "Replace FROMCHAR with TOCHAR in STRING each time it occurs.
Unless optional argument INPLACE is non-nil, return a new string."
  (let ((i (length string))
	(newstr (if inplace string (copy-sequence string))))
    (while (> i 0)
      (setq i (1- i))
      (if (eq (aref newstr i) fromchar)
	  (aset newstr i tochar)))
    newstr))

(defun replace-regexp-in-string (regexp rep string &optional
					fixedcase literal subexp start)
  "Replace all matches for REGEXP with REP in STRING.

Return a new string containing the replacements.

Optional arguments FIXEDCASE, LITERAL and SUBEXP are like the
arguments with the same names of function `replace-match'.  If START
is non-nil, start replacements at that index in STRING.

REP is either a string used as the NEWTEXT arg of `replace-match' or a
function.  If it is a function it is applied to each match to generate
the replacement passed to `replace-match'; the match-data at this
point are such that match 0 is the function's argument.

To replace only the first match (if any), make REGEXP match up to \\'
and replace a sub-expression, e.g.
  (replace-regexp-in-string \"\\(foo\\).*\\'\" \"bar\" \" foo foo\" nil nil 1)
    => \" bar foo\"
"

  ;; To avoid excessive consing from multiple matches in long strings,
  ;; don't just call `replace-match' continually.  Walk down the
  ;; string looking for matches of REGEXP and building up a (reversed)
  ;; list MATCHES.  This comprises segments of STRING which weren't
  ;; matched interspersed with replacements for segments that were.
  ;; [For a `large' number of replacements it's more efficient to
  ;; operate in a temporary buffer; we can't tell from the function's
  ;; args whether to choose the buffer-based implementation, though it
  ;; might be reasonable to do so for long enough STRING.]
  (let ((l (length string))
	(start (or start 0))
	matches str mb me)
    (save-match-data
      (while (and (< start l) (string-match regexp string start))
	(setq mb (match-beginning 0)
	      me (match-end 0))
	;; If we matched the empty string, make sure we advance by one char
	(when (= me mb) (setq me (min l (1+ mb))))
	;; Generate a replacement for the matched substring.
	;; Operate only on the substring to minimize string consing.
	;; Set up match data for the substring for replacement;
	;; presumably this is likely to be faster than munging the
	;; match data directly in Lisp.
	(string-match regexp (setq str (substring string mb me)))
	(setq matches
	      (cons (replace-match (if (stringp rep)
				       rep
				     (funcall rep (match-string 0 str)))
				   fixedcase literal str subexp)
		    (cons (substring string start mb) ; unmatched prefix
			  matches)))
	(setq start me))
      ;; Reconstruct a string from the pieces.
      (setq matches (cons (substring string start l) matches)) ; leftover
      (apply #'concat (nreverse matches)))))
\f
(defun shell-quote-argument (argument)
  "Quote an argument for passing as argument to an inferior shell."
  (if (eq system-type 'ms-dos)
      ;; Quote using double quotes, but escape any existing quotes in
      ;; the argument with backslashes.
      (let ((result "")
	    (start 0)
	    end)
	(if (or (null (string-match "[^\"]" argument))
		(< (match-end 0) (length argument)))
	    (while (string-match "[\"]" argument start)
	      (setq end (match-beginning 0)
		    result (concat result (substring argument start end)
				   "\\" (substring argument end (1+ end)))
		    start (1+ end))))
	(concat "\"" result (substring argument start) "\""))
    (if (eq system-type 'windows-nt)
	(concat "\"" argument "\"")
      (if (equal argument "")
	  "''"
	;; Quote everything except POSIX filename characters.
	;; This should be safe enough even for really weird shells.
	(let ((result "") (start 0) end)
	  (while (string-match "[^-0-9a-zA-Z_./]" argument start)
	    (setq end (match-beginning 0)
		  result (concat result (substring argument start end)
				 "\\" (substring argument end (1+ end)))
		  start (1+ end)))
	  (concat result (substring argument start)))))))

(defun make-syntax-table (&optional oldtable)
  "Return a new syntax table.
Create a syntax table which inherits from OLDTABLE (if non-nil) or
from `standard-syntax-table' otherwise."
  (let ((table (make-char-table 'syntax-table nil)))
    (set-char-table-parent table (or oldtable (standard-syntax-table)))
    table))

(defun add-to-invisibility-spec (arg)
  "Add elements to `buffer-invisibility-spec'.
See documentation for `buffer-invisibility-spec' for the kind of elements
that can be added."
  (cond
   ((or (null buffer-invisibility-spec) (eq buffer-invisibility-spec t))
	(setq buffer-invisibility-spec (list arg)))
   (t
    (setq buffer-invisibility-spec
	  (cons arg buffer-invisibility-spec)))))

(defun remove-from-invisibility-spec (arg)
  "Remove elements from `buffer-invisibility-spec'."
  (if (consp buffer-invisibility-spec)
    (setq buffer-invisibility-spec (delete arg buffer-invisibility-spec))))
\f
(defun global-set-key (key command)
  "Give KEY a global binding as COMMAND.
COMMAND is the command definition to use; usually it is
a symbol naming an interactively-callable function.
KEY is a key sequence; noninteractively, it is a string or vector
of characters or event types, and non-ASCII characters with codes
above 127 (such as ISO Latin-1) can be included if you use a vector.

Note that if KEY has a local binding in the current buffer,
that local binding will continue to shadow any global binding
that you make with this function."
  (interactive "KSet key globally: \nCSet key %s to command: ")
  (or (vectorp key) (stringp key)
      (signal 'wrong-type-argument (list 'arrayp key)))
  (define-key (current-global-map) key command))

(defun local-set-key (key command)
  "Give KEY a local binding as COMMAND.
COMMAND is the command definition to use; usually it is
a symbol naming an interactively-callable function.
KEY is a key sequence; noninteractively, it is a string or vector
of characters or event types, and non-ASCII characters with codes
above 127 (such as ISO Latin-1) can be included if you use a vector.

The binding goes in the current buffer's local map,
which in most cases is shared with all other buffers in the same major mode."
  (interactive "KSet key locally: \nCSet key %s locally to command: ")
  (let ((map (current-local-map)))
    (or map
	(use-local-map (setq map (make-sparse-keymap))))
    (or (vectorp key) (stringp key)
	(signal 'wrong-type-argument (list 'arrayp key)))
    (define-key map key command)))

(defun global-unset-key (key)
  "Remove global binding of KEY.
KEY is a string representing a sequence of keystrokes."
  (interactive "kUnset key globally: ")
  (global-set-key key nil))

(defun local-unset-key (key)
  "Remove local binding of KEY.
KEY is a string representing a sequence of keystrokes."
  (interactive "kUnset key locally: ")
  (if (current-local-map)
      (local-set-key key nil))
  nil)
\f
;; We put this here instead of in frame.el so that it's defined even on
;; systems where frame.el isn't loaded.
(defun frame-configuration-p (object)
  "Return non-nil if OBJECT seems to be a frame configuration.
Any list whose car is `frame-configuration' is assumed to be a frame
configuration."
  (and (consp object)
       (eq (car object) 'frame-configuration)))

(defun functionp (object)
  "Non-nil iff OBJECT is a type of object that can be called as a function."
  (or (and (symbolp object) (fboundp object)
	   (setq object (indirect-function object))
	   (eq (car-safe object) 'autoload)
	   (not (car-safe (cdr-safe (cdr-safe (cdr-safe (cdr-safe object)))))))
      (subrp object) (byte-code-function-p object)
      (eq (car-safe object) 'lambda)))

(defun interactive-form (function)
  "Return the interactive form of FUNCTION.
If function is a command (see `commandp'), value is a list of the form
\(interactive SPEC).  If function is not a command, return nil."
  (setq function (indirect-function function))
  (when (commandp function)
    (cond ((byte-code-function-p function)
	   (when (> (length function) 5)
	     (let ((spec (aref function 5)))
	       (if spec
		   (list 'interactive spec)
		 (list 'interactive)))))
	  ((subrp function)
	   (subr-interactive-form function))
	  ((eq (car-safe function) 'lambda)
	   (setq function (cddr function))
	   (when (stringp (car function))
	     (setq function (cdr function)))
	   (let ((form (car function)))
	     (when (eq (car-safe form) 'interactive)
	       (copy-sequence form)))))))

(defun assq-delete-all (key alist)
  "Delete from ALIST all elements whose car is KEY.
Return the modified alist."
  (let ((tail alist))
    (while tail
      (if (eq (car (car tail)) key)
	  (setq alist (delq (car tail) alist)))
      (setq tail (cdr tail)))
    alist))

(defun make-temp-file (prefix &optional dir-flag)
  "Create a temporary file.
The returned file name (created by appending some random characters at the end
of PREFIX, and expanding against `temporary-file-directory' if necessary,
is guaranteed to point to a newly created empty file.
You can then use `write-region' to write new data into the file.

If DIR-FLAG is non-nil, create a new empty directory instead of a file."
  (let (file)
    (while (condition-case ()
	       (progn
		 (setq file
		       (make-temp-name
			(expand-file-name prefix temporary-file-directory)))
		 (if dir-flag
		     (make-directory file)
		   (write-region "" nil file nil 'silent nil 'excl))
		 nil)
	     (file-already-exists t))
      ;; the file was somehow created by someone else between
      ;; `make-temp-name' and `write-region', let's try again.
      nil)
    file))

\f
(defun add-minor-mode (toggle name &optional keymap after toggle-fun)
  "Register a new minor mode.

This is an XEmacs-compatibility function.  Use `define-minor-mode' instead.

TOGGLE is a symbol which is the name of a buffer-local variable that
is toggled on or off to say whether the minor mode is active or not.

NAME specifies what will appear in the mode line when the minor mode
is active.  NAME should be either a string starting with a space, or a
symbol whose value is such a string.

Optional KEYMAP is the keymap for the minor mode that will be added
to `minor-mode-map-alist'.

Optional AFTER specifies that TOGGLE should be added after AFTER
in `minor-mode-alist'.

Optional TOGGLE-FUN is an interactive function to toggle the mode.
It defaults to (and should by convention be) TOGGLE.

If TOGGLE has a non-nil `:included' property, an entry for the mode is
included in the mode-line minor mode menu.
If TOGGLE has a `:menu-tag', that is used for the menu item's label."
  (unless toggle-fun (setq toggle-fun toggle))
  ;; Add the name to the minor-mode-alist.
  (when name
    (let ((existing (assq toggle minor-mode-alist)))
      (when (and (stringp name) (not (get-text-property 0 'local-map name)))
	(setq name
	      (propertize name
			  'local-map mode-line-minor-mode-keymap
			  'help-echo "mouse-3: minor mode menu")))
      (if existing
	  (setcdr existing (list name))
	(let ((tail minor-mode-alist) found)
	  (while (and tail (not found))
	    (if (eq after (caar tail))
		(setq found tail)
	      (setq tail (cdr tail))))
	  (if found
	      (let ((rest (cdr found)))
		(setcdr found nil)
		(nconc found (list (list toggle name)) rest))
	    (setq minor-mode-alist (cons (list toggle name)
					 minor-mode-alist)))))))
  ;; Add the toggle to the minor-modes menu if requested.
  (when (get toggle :included)
    (define-key mode-line-mode-menu
      (vector toggle)
      (list 'menu-item
	    (concat
	     (or (get toggle :menu-tag)
		 (if (stringp name) name (symbol-name toggle)))
	     (let ((mode-name (if (stringp name) name
				(if (symbolp name) (symbol-value name)))))
	       (if mode-name
		   (concat " (" mode-name ")"))))
	    toggle-fun
	    :button (cons :toggle toggle))))

  ;; Add the map to the minor-mode-map-alist.    
  (when keymap
    (let ((existing (assq toggle minor-mode-map-alist)))
      (if existing
	  (setcdr existing keymap)
	(let ((tail minor-mode-map-alist) found)
	  (while (and tail (not found))
	    (if (eq after (caar tail))
		(setq found tail)
	      (setq tail (cdr tail))))
	  (if found
	      (let ((rest (cdr found)))
		(setcdr found nil)
		(nconc found (list (cons toggle keymap)) rest))
	    (setq minor-mode-map-alist (cons (cons toggle keymap)
					     minor-mode-map-alist))))))))

;; XEmacs compatibility/convenience.
(if (fboundp 'play-sound)
    (defun play-sound-file (file &optional volume device)
      "Play sound stored in FILE.
VOLUME and DEVICE correspond to the keywords of the sound
specification for `play-sound'."
      (interactive "fPlay sound file: ")
      (let ((sound (list :file file)))
	(if volume
	    (plist-put sound :volume volume))
	(if device
	    (plist-put sound :device device))
	(push 'sound sound)
	(play-sound sound))))

;; Clones ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(defun text-clone-maintain (ol1 after beg end &optional len)
  "Propagate the changes made under the overlay OL1 to the other clones.
This is used on the `modification-hooks' property of text clones."
  (when (and after (not undo-in-progress) (overlay-start ol1))
    (let ((margin (if (overlay-get ol1 'text-clone-spreadp) 1 0)))
      (setq beg (max beg (+ (overlay-start ol1) margin)))
      (setq end (min end (- (overlay-end ol1) margin)))
      (when (<= beg end)
	(save-excursion
	  (when (overlay-get ol1 'text-clone-syntax)
	    ;; Check content of the clone's text.
	    (let ((cbeg (+ (overlay-start ol1) margin))
		  (cend (- (overlay-end ol1) margin)))
	      (goto-char cbeg)
	      (save-match-data
		(if (not (re-search-forward
			  (overlay-get ol1 'text-clone-syntax) cend t))
		    ;; Mark the overlay for deletion.
		    (overlay-put ol1 'text-clones nil)
		  (when (< (match-end 0) cend)
		    ;; Shrink the clone at its end.
		    (setq end (min end (match-end 0)))
		    (move-overlay ol1 (overlay-start ol1)
				  (+ (match-end 0) margin)))
		  (when (> (match-beginning 0) cbeg)
		    ;; Shrink the clone at its beginning.
		    (setq beg (max (match-beginning 0) beg))
		    (move-overlay ol1 (- (match-beginning 0) margin)
				  (overlay-end ol1)))))))
	  ;; Now go ahead and update the clones.
	  (let ((head (- beg (overlay-start ol1)))
		(tail (- (overlay-end ol1) end))
		(str (buffer-substring beg end))
		(nothing-left t)
		(inhibit-modification-hooks t))
	    (dolist (ol2 (overlay-get ol1 'text-clones))
	      (let ((oe (overlay-end ol2)))
		(unless (or (eq ol1 ol2) (null oe))
		  (setq nothing-left nil)
		  (let ((mod-beg (+ (overlay-start ol2) head)))
		    ;;(overlay-put ol2 'modification-hooks nil)
		    (goto-char (- (overlay-end ol2) tail))
		    (unless (> mod-beg (point))
		      (save-excursion (insert str))
		      (delete-region mod-beg (point)))
		    ;;(overlay-put ol2 'modification-hooks '(text-clone-maintain))
		    ))))
	    (if nothing-left (delete-overlay ol1))))))))

(defun text-clone-create (start end &optional spreadp syntax)
  "Create a text clone of START...END at point.
Text clones are chunks of text that are automatically kept identical:
changes done to one of the clones will be immediately propagated to the other.

The buffer's content at point is assumed to be already identical to
the one between START and END.
If SYNTAX is provided it's a regexp that describes the possible text of
the clones; the clone will be shrunk or killed if necessary to ensure that
its text matches the regexp.
If SPREADP is non-nil it indicates that text inserted before/after the
clone should be incorporated in the clone."
  ;; To deal with SPREADP we can either use an overlay with `nil t' along
  ;; with insert-(behind|in-front-of)-hooks or use a slightly larger overlay
  ;; (with a one-char margin at each end) with `t nil'.
  ;; We opted for a larger overlay because it behaves better in the case
  ;; where the clone is reduced to the empty string (we want the overlay to
  ;; stay when the clone's content is the empty string and we want to use
  ;; `evaporate' to make sure those overlays get deleted when needed).
  ;; 
  (let* ((pt-end (+ (point) (- end start)))
  	 (start-margin (if (or (not spreadp) (bobp) (<= start (point-min)))
			   0 1))
  	 (end-margin (if (or (not spreadp)
			     (>= pt-end (point-max))
  			     (>= start (point-max)))
  			 0 1))
  	 (ol1 (make-overlay (- start start-margin) (+ end end-margin) nil t))
  	 (ol2 (make-overlay (- (point) start-margin) (+ pt-end end-margin) nil t))
	 (dups (list ol1 ol2)))
    (overlay-put ol1 'modification-hooks '(text-clone-maintain))
    (when spreadp (overlay-put ol1 'text-clone-spreadp t))
    (when syntax (overlay-put ol1 'text-clone-syntax syntax))
    ;;(overlay-put ol1 'face 'underline)
    (overlay-put ol1 'evaporate t)
    (overlay-put ol1 'text-clones dups)
    ;; 
    (overlay-put ol2 'modification-hooks '(text-clone-maintain))
    (when spreadp (overlay-put ol2 'text-clone-spreadp t))
    (when syntax (overlay-put ol2 'text-clone-syntax syntax))
    ;;(overlay-put ol2 'face 'underline)
    (overlay-put ol2 'evaporate t)
    (overlay-put ol2 'text-clones dups)))

;;; subr.el ends here