replace.el

;;; replace.el --- replace commands for Emacs

;; Copyright (C) 1985, 1986, 1987, 1992, 1994, 1996, 1997, 2000, 2001,
;;   2002, 2003, 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.

;; Maintainer: FSF

;; 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 3 of the License, 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.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; This package supplies the string and regular-expression replace functions
;; documented in the Emacs user's manual.

;;; Code:

(defcustom case-replace t
  "*Non-nil means `query-replace' should preserve case in replacements."
  :type 'boolean
  :group 'matching)

(defvar query-replace-history nil)

(defvar query-replace-defaults nil
  "Default values of FROM-STRING and TO-STRING for `query-replace'.
This is a cons cell (FROM-STRING . TO-STRING), or nil if there is
no default value.")

(defvar query-replace-interactive nil
  "Non-nil means `query-replace' uses the last search string.
That becomes the \"string to replace\".")

(defcustom query-replace-from-history-variable 'query-replace-history
  "History list to use for the FROM argument of `query-replace' commands.
The value of this variable should be a symbol; that symbol
is used as a variable to hold a history list for the strings
or patterns to be replaced."
  :group 'matching
  :type 'symbol
  :version "20.3")

(defcustom query-replace-to-history-variable 'query-replace-history
  "History list to use for the TO argument of `query-replace' commands.
The value of this variable should be a symbol; that symbol
is used as a variable to hold a history list for replacement
strings or patterns."
  :group 'matching
  :type 'symbol
  :version "20.3")

(defcustom query-replace-skip-read-only nil
  "*Non-nil means `query-replace' and friends ignore read-only matches."
  :type 'boolean
  :group 'matching
  :version "22.1")

(defcustom query-replace-show-replacement t
  "*Non-nil means to show what actual replacement text will be."
  :type 'boolean
  :group 'matching
  :version "23.1")

(defcustom query-replace-highlight t
  "*Non-nil means to highlight matches during query replacement."
  :type 'boolean
  :group 'matching)

(defcustom query-replace-lazy-highlight t
  "*Controls the lazy-highlighting during query replacements.
When non-nil, all text in the buffer matching the current match
is highlighted lazily using isearch lazy highlighting (see
`lazy-highlight-initial-delay' and `lazy-highlight-interval')."
  :type 'boolean
  :group 'lazy-highlight
  :group 'matching
  :version "22.1")

(defface query-replace
  '((t (:inherit isearch)))
  "Face for highlighting query replacement matches."
  :group 'matching
  :version "22.1")

(defun query-replace-descr (string)
  (mapconcat 'isearch-text-char-description string ""))

(defun query-replace-read-from (prompt regexp-flag)
  "Query and return the `from' argument of a query-replace operation.
The return value can also be a pair (FROM . TO) indicating that the user
wants to replace FROM with TO."
  (if query-replace-interactive
      (car (if regexp-flag regexp-search-ring search-ring))
    (let* ((history-add-new-input nil)
	   (from
	    ;; The save-excursion here is in case the user marks and copies
	    ;; a region in order to specify the minibuffer input.
	    ;; That should not clobber the region for the query-replace itself.
	    (save-excursion
	      (read-from-minibuffer
	       (if query-replace-defaults
		   (format "%s (default %s -> %s): " prompt
			   (query-replace-descr (car query-replace-defaults))
			   (query-replace-descr (cdr query-replace-defaults)))
		 (format "%s: " prompt))
	       nil nil nil
	       query-replace-from-history-variable
	       nil t))))
      (if (and (zerop (length from)) query-replace-defaults)
	  (cons (car query-replace-defaults)
		(query-replace-compile-replacement
		 (cdr query-replace-defaults) regexp-flag))
	(add-to-history query-replace-from-history-variable from nil t)
	;; Warn if user types \n or \t, but don't reject the input.
	(and regexp-flag
	     (string-match "\\(\\`\\|[^\\]\\)\\(\\\\\\\\\\)*\\(\\\\[nt]\\)" from)
	     (let ((match (match-string 3 from)))
	       (cond
		((string= match "\\n")
		 (message "Note: `\\n' here doesn't match a newline; to do that, type C-q C-j instead"))
		((string= match "\\t")
		 (message "Note: `\\t' here doesn't match a tab; to do that, just type TAB")))
	       (sit-for 2)))
	from))))

(defun query-replace-compile-replacement (to regexp-flag)
  "Maybe convert a regexp replacement TO to Lisp.
Returns a list suitable for `perform-replace' if necessary,
the original string if not."
  (if (and regexp-flag
	   (string-match "\\(\\`\\|[^\\]\\)\\(\\\\\\\\\\)*\\\\[,#]" to))
      (let (pos list char)
	(while
	    (progn
	      (setq pos (match-end 0))
	      (push (substring to 0 (- pos 2)) list)
	      (setq char (aref to (1- pos))
		    to (substring to pos))
	      (cond ((eq char ?\#)
		     (push '(number-to-string replace-count) list))
		    ((eq char ?\,)
		     (setq pos (read-from-string to))
		     (push `(replace-quote ,(car pos)) list)
		     (let ((end
			    ;; Swallow a space after a symbol
			    ;; if there is a space.
			    (if (and (or (symbolp (car pos))
					 ;; Swallow a space after 'foo
					 ;; but not after (quote foo).
					 (and (eq (car-safe (car pos)) 'quote)
					      (not (= ?\( (aref to 0)))))
				     (eq (string-match " " to (cdr pos))
					 (cdr pos)))
				(1+ (cdr pos))
			      (cdr pos))))
		       (setq to (substring to end)))))
	      (string-match "\\(\\`\\|[^\\]\\)\\(\\\\\\\\\\)*\\\\[,#]" to)))
	(setq to (nreverse (delete "" (cons to list))))
	(replace-match-string-symbols to)
	(cons 'replace-eval-replacement
	      (if (cdr to)
		  (cons 'concat to)
		(car to))))
    to))


(defun query-replace-read-to (from prompt regexp-flag)
  "Query and return the `to' argument of a query-replace operation."
  (query-replace-compile-replacement
   (save-excursion
     (let* ((history-add-new-input nil)
	    (to (read-from-minibuffer
		 (format "%s %s with: " prompt (query-replace-descr from))
		 nil nil nil
		 query-replace-to-history-variable from t)))
       (add-to-history query-replace-to-history-variable to nil t)
       (setq query-replace-defaults (cons from to))
       to))
   regexp-flag))

(defun query-replace-read-args (prompt regexp-flag &optional noerror)
  (unless noerror
    (barf-if-buffer-read-only))
  (let* ((from (query-replace-read-from prompt regexp-flag))
	 (to (if (consp from) (prog1 (cdr from) (setq from (car from)))
	       (query-replace-read-to from prompt regexp-flag))))
    (list from to current-prefix-arg)))

(defun query-replace (from-string to-string &optional delimited start end)
  "Replace some occurrences of FROM-STRING with TO-STRING.
As each match is found, the user must type a character saying
what to do with it.  For directions, type \\[help-command] at that time.

In Transient Mark mode, if the mark is active, operate on the contents
of the region.  Otherwise, operate from point to the end of the buffer.

If `query-replace-interactive' is non-nil, the last incremental search
string is used as FROM-STRING--you don't have to specify it with the
minibuffer.

Matching is independent of case if `case-fold-search' is non-nil and
FROM-STRING has no uppercase letters.  Replacement transfers the case
pattern of the old text to the new text, if `case-replace' and
`case-fold-search' are non-nil and FROM-STRING has no uppercase
letters.  \(Transferring the case pattern means that if the old text
matched is all caps, or capitalized, then its replacement is upcased
or capitalized.)

Third arg DELIMITED (prefix arg if interactive), if non-nil, means replace
only matches surrounded by word boundaries.
Fourth and fifth arg START and END specify the region to operate on.

To customize possible responses, change the \"bindings\" in `query-replace-map'."
  (interactive
   (let ((common
	  (query-replace-read-args
	   (concat "Query replace"
		   (if current-prefix-arg " word" "")
		   (if (and transient-mark-mode mark-active) " in region" ""))
	   nil)))
     (list (nth 0 common) (nth 1 common) (nth 2 common)
	   ;; These are done separately here
	   ;; so that command-history will record these expressions
	   ;; rather than the values they had this time.
	   (if (and transient-mark-mode mark-active)
	       (region-beginning))
	   (if (and transient-mark-mode mark-active)
	       (region-end)))))
  (perform-replace from-string to-string t nil delimited nil nil start end))

(define-key esc-map "%" 'query-replace)

(defun query-replace-regexp (regexp to-string &optional delimited start end)
  "Replace some things after point matching REGEXP with TO-STRING.
As each match is found, the user must type a character saying
what to do with it.  For directions, type \\[help-command] at that time.

In Transient Mark mode, if the mark is active, operate on the contents
of the region.  Otherwise, operate from point to the end of the buffer.

If `query-replace-interactive' is non-nil, the last incremental search
regexp is used as REGEXP--you don't have to specify it with the
minibuffer.

Matching is independent of case if `case-fold-search' is non-nil and
REGEXP has no uppercase letters.  Replacement transfers the case
pattern of the old text to the new text, if `case-replace' and
`case-fold-search' are non-nil and REGEXP has no uppercase letters.
\(Transferring the case pattern means that if the old text matched is
all caps, or capitalized, then its replacement is upcased or
capitalized.)

Third arg DELIMITED (prefix arg if interactive), if non-nil, means replace
only matches surrounded by word boundaries.
Fourth and fifth arg START and END specify the region to operate on.

In TO-STRING, `\\&' stands for whatever matched the whole of REGEXP,
and `\\=\\N' (where N is a digit) stands for
whatever what matched the Nth `\\(...\\)' in REGEXP.
`\\?' lets you edit the replacement text in the minibuffer
at the given position for each replacement.

In interactive calls, the replacement text can contain `\\,'
followed by a Lisp expression.  Each
replacement evaluates that expression to compute the replacement
string.  Inside of that expression, `\\&' is a string denoting the
whole match as a string, `\\N' for a partial match, `\\#&' and `\\#N'
for the whole or a partial match converted to a number with
`string-to-number', and `\\#' itself for the number of replacements
done so far (starting with zero).

If the replacement expression is a symbol, write a space after it
to terminate it.  One space there, if any, will be discarded.

When using those Lisp features interactively in the replacement
text, TO-STRING is actually made a list instead of a string.
Use \\[repeat-complex-command] after this command for details."
  (interactive
   (let ((common
	  (query-replace-read-args
	   (concat "Query replace"
		   (if current-prefix-arg " word" "")
		   " regexp"
		   (if (and transient-mark-mode mark-active) " in region" ""))
	   t)))
     (list (nth 0 common) (nth 1 common) (nth 2 common)
	   ;; These are done separately here
	   ;; so that command-history will record these expressions
	   ;; rather than the values they had this time.
	   (if (and transient-mark-mode mark-active)
	       (region-beginning))
	   (if (and transient-mark-mode mark-active)
	       (region-end)))))
  (perform-replace regexp to-string t t delimited nil nil start end))

(define-key esc-map [?\C-%] 'query-replace-regexp)

(defun query-replace-regexp-eval (regexp to-expr &optional delimited start end)
  "Replace some things after point matching REGEXP with the result of TO-EXPR.

Interactive use of this function is deprecated in favor of the
`\\,' feature of `query-replace-regexp'.  For non-interactive use, a loop
using `search-forward-regexp' and `replace-match' is preferred.

As each match is found, the user must type a character saying
what to do with it.  For directions, type \\[help-command] at that time.

TO-EXPR is a Lisp expression evaluated to compute each replacement.  It may
reference `replace-count' to get the number of replacements already made.
If the result of TO-EXPR is not a string, it is converted to one using
`prin1-to-string' with the NOESCAPE argument (which see).

For convenience, when entering TO-EXPR interactively, you can use `\\&' or
`\\0' to stand for whatever matched the whole of REGEXP, and `\\N' (where
N is a digit) to stand for whatever matched the Nth `\\(...\\)' in REGEXP.
Use `\\#&' or `\\#N' if you want a number instead of a string.
In interactive use, `\\#' in itself stands for `replace-count'.

In Transient Mark mode, if the mark is active, operate on the contents
of the region.  Otherwise, operate from point to the end of the buffer.

If `query-replace-interactive' is non-nil, the last incremental search
regexp is used as REGEXP--you don't have to specify it with the
minibuffer.

Preserves case in each replacement if `case-replace' and `case-fold-search'
are non-nil and REGEXP has no uppercase letters.

Third arg DELIMITED (prefix arg if interactive), if non-nil, means replace
only matches that are surrounded by word boundaries.
Fourth and fifth arg START and END specify the region to operate on."
  (interactive
   (progn
   (barf-if-buffer-read-only)
   (let* ((from
	   ;; Let-bind the history var to disable the "foo -> bar" default.
	   ;; Maybe we shouldn't disable this default, but for now I'll
	   ;; leave it off.  --Stef
	   (let ((query-replace-to-history-variable nil))
	     (query-replace-read-from "Query replace regexp" t)))
	  (to (list (read-from-minibuffer
		     (format "Query replace regexp %s with eval: "
			     (query-replace-descr from))
		     nil nil t query-replace-to-history-variable from t))))
     ;; We make TO a list because replace-match-string-symbols requires one,
     ;; and the user might enter a single token.
     (replace-match-string-symbols to)
     (list from (car to) current-prefix-arg
	   (if (and transient-mark-mode mark-active)
	       (region-beginning))
	   (if (and transient-mark-mode mark-active)
	       (region-end))))))
  (perform-replace regexp (cons 'replace-eval-replacement to-expr)
		   t 'literal delimited nil nil start end))

(make-obsolete 'query-replace-regexp-eval
  "for interactive use, use the special `\\,' feature of
`query-replace-regexp' instead.  Non-interactively, a loop
using `search-forward-regexp' and `replace-match' is preferred." "22.1")

(defun map-query-replace-regexp (regexp to-strings &optional n start end)
  "Replace some matches for REGEXP with various strings, in rotation.
The second argument TO-STRINGS contains the replacement strings, separated
by spaces.  This command works like `query-replace-regexp' except that
each successive replacement uses the next successive replacement string,
wrapping around from the last such string to the first.

In Transient Mark mode, if the mark is active, operate on the contents
of the region.  Otherwise, operate from point to the end of the buffer.

Non-interactively, TO-STRINGS may be a list of replacement strings.

If `query-replace-interactive' is non-nil, the last incremental search
regexp is used as REGEXP--you don't have to specify it with the minibuffer.

A prefix argument N says to use each replacement string N times
before rotating to the next.
Fourth and fifth arg START and END specify the region to operate on."
  (interactive
   (let* ((from (if query-replace-interactive
		    (car regexp-search-ring)
		  (read-from-minibuffer "Map query replace (regexp): "
					nil nil nil
					'query-replace-history nil t)))
	  (to (read-from-minibuffer
	       (format "Query replace %s with (space-separated strings): "
		       (query-replace-descr from))
	       nil nil nil
	       'query-replace-history from t)))
     (list from to
	   (and current-prefix-arg
		(prefix-numeric-value current-prefix-arg))
	   (if (and transient-mark-mode mark-active)
	       (region-beginning))
	   (if (and transient-mark-mode mark-active)
	       (region-end)))))
  (let (replacements)
    (if (listp to-strings)
	(setq replacements to-strings)
      (while (/= (length to-strings) 0)
	(if (string-match " " to-strings)
	    (setq replacements
		  (append replacements
			  (list (substring to-strings 0
					   (string-match " " to-strings))))
		  to-strings (substring to-strings
				       (1+ (string-match " " to-strings))))
	  (setq replacements (append replacements (list to-strings))
		to-strings ""))))
    (perform-replace regexp replacements t t nil n nil start end)))

(defun replace-string (from-string to-string &optional delimited start end)
  "Replace occurrences of FROM-STRING with TO-STRING.
Preserve case in each match if `case-replace' and `case-fold-search'
are non-nil and FROM-STRING has no uppercase letters.
\(Preserving case means that if the string matched is all caps, or capitalized,
then its replacement is upcased or capitalized.)

In Transient Mark mode, if the mark is active, operate on the contents
of the region.  Otherwise, operate from point to the end of the buffer.

Third arg DELIMITED (prefix arg if interactive), if non-nil, means replace
only matches surrounded by word boundaries.
Fourth and fifth arg START and END specify the region to operate on.

If `query-replace-interactive' is non-nil, the last incremental search
string is used as FROM-STRING--you don't have to specify it with the
minibuffer.

This function is usually the wrong thing to use in a Lisp program.
What you probably want is a loop like this:
  (while (search-forward FROM-STRING nil t)
    (replace-match TO-STRING nil t))
which will run faster and will not set the mark or print anything.
\(You may need a more complex loop if FROM-STRING can match the null string
and TO-STRING is also null.)"
  (interactive
   (let ((common
	  (query-replace-read-args
	   (concat "Replace"
		   (if current-prefix-arg " word" "")
		   " string"
		   (if (and transient-mark-mode mark-active) " in region" ""))
	   nil)))
     (list (nth 0 common) (nth 1 common) (nth 2 common)
	   (if (and transient-mark-mode mark-active)
	       (region-beginning))
	   (if (and transient-mark-mode mark-active)
	       (region-end)))))
  (perform-replace from-string to-string nil nil delimited nil nil start end))

(defun replace-regexp (regexp to-string &optional delimited start end)
  "Replace things after point matching REGEXP with TO-STRING.
Preserve case in each match if `case-replace' and `case-fold-search'
are non-nil and REGEXP has no uppercase letters.

In Transient Mark mode, if the mark is active, operate on the contents
of the region.  Otherwise, operate from point to the end of the buffer.

Third arg DELIMITED (prefix arg if interactive), if non-nil, means replace
only matches surrounded by word boundaries.
Fourth and fifth arg START and END specify the region to operate on.

In TO-STRING, `\\&' stands for whatever matched the whole of REGEXP,
and `\\=\\N' (where N is a digit) stands for
whatever what matched the Nth `\\(...\\)' in REGEXP.
`\\?' lets you edit the replacement text in the minibuffer
at the given position for each replacement.

In interactive calls, the replacement text may contain `\\,'
followed by a Lisp expression used as part of the replacement
text.  Inside of that expression, `\\&' is a string denoting the
whole match, `\\N' a partial match, `\\#&' and `\\#N' the respective
numeric values from `string-to-number', and `\\#' itself for
`replace-count', the number of replacements occurred so far.

If your Lisp expression is an identifier and the next letter in
the replacement string would be interpreted as part of it, you
can wrap it with an expression like `\\,(or \\#)'.  Incidentally,
for this particular case you may also enter `\\#' in the
replacement text directly.

When using those Lisp features interactively in the replacement
text, TO-STRING is actually made a list instead of a string.
Use \\[repeat-complex-command] after this command for details.

If `query-replace-interactive' is non-nil, the last incremental search
regexp is used as REGEXP--you don't have to specify it with the minibuffer.

This function is usually the wrong thing to use in a Lisp program.
What you probably want is a loop like this:
  (while (re-search-forward REGEXP nil t)
    (replace-match TO-STRING nil nil))
which will run faster and will not set the mark or print anything."
  (interactive
   (let ((common
	  (query-replace-read-args
	   (concat "Replace"
		   (if current-prefix-arg " word" "")
		   " regexp"
		   (if (and transient-mark-mode mark-active) " in region" ""))
	   t)))
     (list (nth 0 common) (nth 1 common) (nth 2 common)
	   (if (and transient-mark-mode mark-active)
	       (region-beginning))
	   (if (and transient-mark-mode mark-active)
	       (region-end)))))
  (perform-replace regexp to-string nil t delimited nil nil start end))


(defvar regexp-history nil
  "History list for some commands that read regular expressions.

Maximum length of the history list is determined by the value
of `history-length', which see.")

(defun read-regexp (prompt &optional default-value)
  "Read regexp as a string using the regexp history and some useful defaults.
Prompt for a regular expression with PROMPT (without a colon and
space) in the minibuffer.  The optional argument DEFAULT-VALUE
provides the value to display in the minibuffer prompt that is
returned if the user just types RET.
Values available via M-n are the string at point, the last isearch
regexp, the last isearch string, and the last replacement regexp."
  (let* ((defaults
	   (list (regexp-quote
		  (or (funcall (or find-tag-default-function
				   (get major-mode 'find-tag-default-function)
				   'find-tag-default))
		      ""))
		 (car regexp-search-ring)
		 (regexp-quote (or (car search-ring) ""))
		 (car (symbol-value
		       query-replace-from-history-variable))))
	 (defaults (delete-dups (delq nil (delete "" defaults))))
	 ;; Don't add automatically the car of defaults for empty input
	 (history-add-new-input nil)
	 (input
	  (read-from-minibuffer
	   (if default-value
	       (format "%s (default %s): " prompt
		       (query-replace-descr default-value))
	     (format "%s: " prompt))
	   nil nil nil 'regexp-history defaults t)))
    (if (equal input "")
	default-value
      (prog1 input
	(add-to-history 'regexp-history input)))))


(defalias 'delete-non-matching-lines 'keep-lines)
(defalias 'delete-matching-lines 'flush-lines)
(defalias 'count-matches 'how-many)


(defun keep-lines-read-args (prompt)
  "Read arguments for `keep-lines' and friends.
Prompt for a regexp with PROMPT.
Value is a list, (REGEXP)."
  (list (read-regexp prompt) nil nil t))

(defun keep-lines (regexp &optional rstart rend interactive)
  "Delete all lines except those containing matches for REGEXP.
A match split across lines preserves all the lines it lies in.
When called from Lisp (and usually interactively as well, see below)
applies to all lines starting after point.

If REGEXP contains upper case characters (excluding those preceded by `\\')
and `search-upper-case' is non-nil, the matching is case-sensitive.

Second and third arg RSTART and REND specify the region to operate on.
This command operates on (the accessible part of) all lines whose
accessible part is entirely contained in the region determined by RSTART
and REND.  (A newline ending a line counts as part of that line.)

Interactively, in Transient Mark mode when the mark is active, operate
on all lines whose accessible part is entirely contained in the region.
Otherwise, the command applies to all lines starting after point.
When calling this function from Lisp, you can pretend that it was
called interactively by passing a non-nil INTERACTIVE argument.

This function starts looking for the next match from the end of
the previous match.  Hence, it ignores matches that overlap
a previously found match."

  (interactive
   (progn
     (barf-if-buffer-read-only)
     (keep-lines-read-args "Keep lines containing match for regexp")))
  (if rstart
      (progn
	(goto-char (min rstart rend))
	(setq rend
	      (progn
		(save-excursion
		  (goto-char (max rstart rend))
		  (unless (or (bolp) (eobp))
		    (forward-line 0))
		  (point-marker)))))
    (if (and interactive transient-mark-mode mark-active)
	(setq rstart (region-beginning)
	      rend (progn
		     (goto-char (region-end))
		     (unless (or (bolp) (eobp))
		       (forward-line 0))
		     (point-marker)))
      (setq rstart (point)
	    rend (point-max-marker)))
    (goto-char rstart))
  (save-excursion
    (or (bolp) (forward-line 1))
    (let ((start (point))
	  (case-fold-search
	   (if (and case-fold-search search-upper-case)
	       (isearch-no-upper-case-p regexp t)
	     case-fold-search)))
      (while (< (point) rend)
	;; Start is first char not preserved by previous match.
	(if (not (re-search-forward regexp rend 'move))
	    (delete-region start rend)
	  (let ((end (save-excursion (goto-char (match-beginning 0))
				     (forward-line 0)
				     (point))))
	    ;; Now end is first char preserved by the new match.
	    (if (< start end)
		(delete-region start end))))

	(setq start (save-excursion (forward-line 1) (point)))
	;; If the match was empty, avoid matching again at same place.
	(and (< (point) rend)
	     (= (match-beginning 0) (match-end 0))
	     (forward-char 1)))))
  (set-marker rend nil)
  nil)


(defun flush-lines (regexp &optional rstart rend interactive)
 "Delete lines containing matches for REGEXP.
When called from Lisp (and usually when called interactively as
well, see below), applies to the part of the buffer after point.
The line point is in is deleted if and only if it contains a
match for regexp starting after point.

If REGEXP contains upper case characters (excluding those preceded by `\\')
and `search-upper-case' is non-nil, the matching is case-sensitive.

Second and third arg RSTART and REND specify the region to operate on.
Lines partially contained in this region are deleted if and only if
they contain a match entirely contained in it.

Interactively, in Transient Mark mode when the mark is active, operate
on the contents of the region.  Otherwise, operate from point to the
end of (the accessible portion of) the buffer.  When calling this function
from Lisp, you can pretend that it was called interactively by passing
a non-nil INTERACTIVE argument.

If a match is split across lines, all the lines it lies in are deleted.
They are deleted _before_ looking for the next match.  Hence, a match
starting on the same line at which another match ended is ignored."

  (interactive
   (progn
     (barf-if-buffer-read-only)
     (keep-lines-read-args "Flush lines containing match for regexp")))
  (if rstart
      (progn
	(goto-char (min rstart rend))
	(setq rend (copy-marker (max rstart rend))))
    (if (and interactive transient-mark-mode mark-active)
	(setq rstart (region-beginning)
	      rend (copy-marker (region-end)))
      (setq rstart (point)
	    rend (point-max-marker)))
    (goto-char rstart))
  (let ((case-fold-search
	 (if (and case-fold-search search-upper-case)
	     (isearch-no-upper-case-p regexp t)
	   case-fold-search)))
    (save-excursion
      (while (and (< (point) rend)
		  (re-search-forward regexp rend t))
	(delete-region (save-excursion (goto-char (match-beginning 0))
				       (forward-line 0)
				       (point))
		       (progn (forward-line 1) (point))))))
  (set-marker rend nil)
  nil)


(defun how-many (regexp &optional rstart rend interactive)
  "Print and return number of matches for REGEXP following point.
When called from Lisp and INTERACTIVE is omitted or nil, just return
the number, do not print it; if INTERACTIVE is t, the function behaves
in all respects as if it had been called interactively.

If REGEXP contains upper case characters (excluding those preceded by `\\')
and `search-upper-case' is non-nil, the matching is case-sensitive.

Second and third arg RSTART and REND specify the region to operate on.

Interactively, in Transient Mark mode when the mark is active, operate
on the contents of the region.  Otherwise, operate from point to the
end of (the accessible portion of) the buffer.

This function starts looking for the next match from the end of
the previous match.  Hence, it ignores matches that overlap
a previously found match."

  (interactive
   (keep-lines-read-args "How many matches for regexp"))
  (save-excursion
    (if rstart
	(progn
	  (goto-char (min rstart rend))
	  (setq rend (max rstart rend)))
      (if (and interactive transient-mark-mode mark-active)
	  (setq rstart (region-beginning)
		rend (region-end))
	(setq rstart (point)
	      rend (point-max)))
      (goto-char rstart))
    (let ((count 0)
	  opoint
	  (case-fold-search
	   (if (and case-fold-search search-upper-case)
	       (isearch-no-upper-case-p regexp t)
	     case-fold-search)))
      (while (and (< (point) rend)
		  (progn (setq opoint (point))
			 (re-search-forward regexp rend t)))
	(if (= opoint (point))
	    (forward-char 1)
	  (setq count (1+ count))))
      (when interactive (message "%d occurrence%s"
				 count
				 (if (= count 1) "" "s")))
      count)))


(defvar occur-mode-map
  (let ((map (make-sparse-keymap)))
    ;; We use this alternative name, so we can use \\[occur-mode-mouse-goto].
    (define-key map [mouse-2] 'occur-mode-mouse-goto)
    (define-key map "\C-c\C-c" 'occur-mode-goto-occurrence)
    (define-key map "\C-m" 'occur-mode-goto-occurrence)
    (define-key map "o" 'occur-mode-goto-occurrence-other-window)
    (define-key map "\C-o" 'occur-mode-display-occurrence)
    (define-key map "\M-n" 'occur-next)
    (define-key map "\M-p" 'occur-prev)
    (define-key map "r" 'occur-rename-buffer)
    (define-key map "c" 'clone-buffer)
    (define-key map "g" 'revert-buffer)
    (define-key map "q" 'quit-window)
    (define-key map "z" 'kill-this-buffer)
    (define-key map "\C-c\C-f" 'next-error-follow-minor-mode)
    (define-key map [menu-bar] (make-sparse-keymap))
    (define-key map [menu-bar occur]
      (cons "Occur" map))
    (define-key map [next-error-follow-minor-mode]
      (menu-bar-make-mm-toggle next-error-follow-minor-mode
			       "Auto Occurrence Display"
			       "Display another occurrence when moving the cursor"))
    (define-key map [separator-1] '("--"))
    (define-key map [kill-this-buffer] 
      '(menu-item "Kill occur buffer" kill-this-buffer
		  :help "Kill the current *Occur* buffer"))
    (define-key map [quit-window] 
      '(menu-item "Quit occur window" quit-window
		  :help "Quit the current *Occur* buffer.  Bury it, and maybe delete the selected frame"))
    (define-key map [revert-buffer] 
      '(menu-item "Revert occur buffer" revert-buffer
		  :help "Replace the text in the *Occur* buffer with the results of rerunning occur"))
    (define-key map [clone-buffer] 
      '(menu-item "Clone occur buffer" clone-buffer
		  :help "Create and return a twin copy of the current *Occur* buffer"))
    (define-key map [occur-rename-buffer] 
      '(menu-item "Rename occur buffer" occur-rename-buffer
		  :help "Rename the current *Occur* buffer to *Occur: original-buffer-name*."))
    (define-key map [separator-2] '("--"))
    (define-key map [occur-mode-goto-occurrence-other-window]
      '(menu-item "Go To Occurrence Other Window" occur-mode-goto-occurrence-other-window
		  :help "Go to the occurrence the current line describes, in another window"))
    (define-key map [occur-mode-goto-occurrence]
      '(menu-item "Go To Occurrence" occur-mode-goto-occurrence
		  :help "Go to the occurrence the current line describes"))
    (define-key map [occur-mode-display-occurrence]
      '(menu-item "Display Occurrence" occur-mode-display-occurrence
		  :help "Display in another window the occurrence the current line describes"))
    (define-key map [occur-next] 
      '(menu-item "Move to next match" occur-next
		  :help "Move to the Nth (default 1) next match in an Occur mode buffer"))
    (define-key map [occur-prev] 
      '(menu-item "Move to previous match" occur-prev
		  :help "Move to the Nth (default 1) previous match in an Occur mode buffer"))
    map)
  "Keymap for `occur-mode'.")

(defvar occur-revert-arguments nil
  "Arguments to pass to `occur-1' to revert an Occur mode buffer.
See `occur-revert-function'.")

(defcustom occur-mode-hook '(turn-on-font-lock)
  "Hook run when entering Occur mode."
  :type 'hook
  :group 'matching)

(defcustom occur-hook nil
  "Hook run by Occur when there are any matches."
  :type 'hook
  :group 'matching)

(defcustom occur-mode-find-occurrence-hook nil
  "Hook run by Occur after locating an occurrence.
This will be called with the cursor position at the occurrence.  An application
for this is to reveal context in an outline-mode when the occurrence is hidden."
  :type 'hook
  :group 'matching)

(put 'occur-mode 'mode-class 'special)
(defun occur-mode ()
  "Major mode for output from \\[occur].
\\<occur-mode-map>Move point to one of the items in this buffer, then use
\\[occur-mode-goto-occurrence] to go to the occurrence that the item refers to.
Alternatively, click \\[occur-mode-mouse-goto] on an item to go to it.

\\{occur-mode-map}"
  (interactive)
  (kill-all-local-variables)
  (use-local-map occur-mode-map)
  (setq major-mode 'occur-mode)
  (setq mode-name "Occur")
  (set (make-local-variable 'revert-buffer-function) 'occur-revert-function)
  (make-local-variable 'occur-revert-arguments)
  (add-hook 'change-major-mode-hook 'font-lock-defontify nil t)
  (setq next-error-function 'occur-next-error)
  (run-mode-hooks 'occur-mode-hook))

(defun occur-revert-function (ignore1 ignore2)
  "Handle `revert-buffer' for Occur mode buffers."
  (apply 'occur-1 (append occur-revert-arguments (list (buffer-name)))))

(defun occur-mode-find-occurrence ()
  (let ((pos (get-text-property (point) 'occur-target)))
    (unless pos
      (error "No occurrence on this line"))
    (unless (buffer-live-p (marker-buffer pos))
      (error "Buffer for this occurrence was killed"))
    pos))

(defalias 'occur-mode-mouse-goto 'occur-mode-goto-occurrence)
(defun occur-mode-goto-occurrence (&optional event)
  "Go to the occurrence the current line describes."
  (interactive (list last-nonmenu-event))
  (let ((pos
         (if (null event)
             ;; Actually `event-end' works correctly with a nil argument as
             ;; well, so we could dispense with this test, but let's not
             ;; rely on this undocumented behavior.
             (occur-mode-find-occurrence)
           (with-current-buffer (window-buffer (posn-window (event-end event)))
             (save-excursion
               (goto-char (posn-point (event-end event)))
               (occur-mode-find-occurrence)))))
        same-window-buffer-names
        same-window-regexps)
    (pop-to-buffer (marker-buffer pos))
    (goto-char pos)
    (run-hooks 'occur-mode-find-occurrence-hook)))

(defun occur-mode-goto-occurrence-other-window ()
  "Go to the occurrence the current line describes, in another window."
  (interactive)
  (let ((pos (occur-mode-find-occurrence)))
    (switch-to-buffer-other-window (marker-buffer pos))
    (goto-char pos)
    (run-hooks 'occur-mode-find-occurrence-hook)))

(defun occur-mode-display-occurrence ()
  "Display in another window the occurrence the current line describes."
  (interactive)
  (let ((pos (occur-mode-find-occurrence))
	window
	;; Bind these to ensure `display-buffer' puts it in another window.
	same-window-buffer-names