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;;; simple.el --- basic editing commands for Emacs  -*- lexical-binding: t -*-
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;; Copyright (C) 1985-1987, 1993-2015 Free Software Foundation, Inc.
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;; Maintainer: emacs-devel@gnu.org
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;; Keywords: internal
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;; Package: emacs
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;; This file is part of GNU Emacs.

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;; GNU Emacs is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
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;; 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
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;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
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;;; Commentary:

;; A grab-bag of basic Emacs commands not specifically related to some
;; major mode or to file-handling.

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;;; Code:
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(eval-when-compile (require 'cl-lib))

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(declare-function widget-convert "wid-edit" (type &rest args))
(declare-function shell-mode "shell" ())
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;;; From compile.el
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(defvar compilation-current-error)
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(defvar compilation-context-lines)
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(defcustom idle-update-delay 0.5
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  "Idle time delay before updating various things on the screen.
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Various Emacs features that update auxiliary information when point moves
wait this many seconds after Emacs becomes idle before doing an update."
  :type 'number
  :group 'display
  :version "22.1")
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(defgroup killing nil
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  "Killing and yanking commands."
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  :group 'editing)

(defgroup paren-matching nil
  "Highlight (un)matching of parens and expressions."
  :group 'matching)
55

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;;; next-error support framework
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(defgroup next-error nil
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  "`next-error' support framework."
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  :group 'compilation
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  :version "22.1")
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(defface next-error
  '((t (:inherit region)))
  "Face used to highlight next error locus."
  :group 'next-error
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  :version "22.1")
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(defcustom next-error-highlight 0.5
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  "Highlighting of locations in selected source buffers.
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If a number, highlight the locus in `next-error' face for the given time
in seconds, or until the next command is executed.
If t, highlight the locus until the next command is executed, or until
some other locus replaces it.
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If nil, don't highlight the locus in the source buffer.
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If `fringe-arrow', indicate the locus by the fringe arrow
indefinitely until some other locus replaces it."
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  :type '(choice (number :tag "Highlight for specified time")
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                 (const :tag "Semipermanent highlighting" t)
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                 (const :tag "No highlighting" nil)
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                 (const :tag "Fringe arrow" fringe-arrow))
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  :group 'next-error
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  :version "22.1")
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(defcustom next-error-highlight-no-select 0.5
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  "Highlighting of locations in `next-error-no-select'.
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If number, highlight the locus in `next-error' face for given time in seconds.
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If t, highlight the locus indefinitely until some other locus replaces it.
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If nil, don't highlight the locus in the source buffer.
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If `fringe-arrow', indicate the locus by the fringe arrow
indefinitely until some other locus replaces it."
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  :type '(choice (number :tag "Highlight for specified time")
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                 (const :tag "Semipermanent highlighting" t)
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                 (const :tag "No highlighting" nil)
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                 (const :tag "Fringe arrow" fringe-arrow))
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  :group 'next-error
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  :version "22.1")
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(defcustom next-error-recenter nil
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  "Display the line in the visited source file recentered as specified.
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If non-nil, the value is passed directly to `recenter'."
  :type '(choice (integer :tag "Line to recenter to")
                 (const :tag "Center of window" (4))
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                 (const :tag "No recentering" nil))
  :group 'next-error
  :version "23.1")

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(defcustom next-error-hook nil
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  "List of hook functions run by `next-error' after visiting source file."
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  :type 'hook
  :group 'next-error)

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(defvar next-error-highlight-timer nil)

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(defvar next-error-overlay-arrow-position nil)
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(put 'next-error-overlay-arrow-position 'overlay-arrow-string (purecopy "=>"))
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(add-to-list 'overlay-arrow-variable-list 'next-error-overlay-arrow-position)

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(defvar next-error-last-buffer nil
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  "The most recent `next-error' buffer.
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A buffer becomes most recent when its compilation, grep, or
similar mode is started, or when it is used with \\[next-error]
or \\[compile-goto-error].")

(defvar next-error-function nil
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  "Function to use to find the next error in the current buffer.
The function is called with 2 parameters:
ARG is an integer specifying by how many errors to move.
RESET is a boolean which, if non-nil, says to go back to the beginning
of the errors before moving.
Major modes providing compile-like functionality should set this variable
to indicate to `next-error' that this is a candidate buffer and how
to navigate in it.")
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(make-variable-buffer-local 'next-error-function)

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(defvar next-error-move-function nil
  "Function to use to move to an error locus.
It takes two arguments, a buffer position in the error buffer
and a buffer position in the error locus buffer.
The buffer for the error locus should already be current.
nil means use goto-char using the second argument position.")
(make-variable-buffer-local 'next-error-move-function)

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(defsubst next-error-buffer-p (buffer
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			       &optional avoid-current
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			       extra-test-inclusive
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			       extra-test-exclusive)
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  "Test if BUFFER is a `next-error' capable buffer.
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If AVOID-CURRENT is non-nil, treat the current buffer
as an absolute last resort only.

The function EXTRA-TEST-INCLUSIVE, if non-nil, is called in each buffer
that normally would not qualify.  If it returns t, the buffer
in question is treated as usable.

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The function EXTRA-TEST-EXCLUSIVE, if non-nil, is called in each buffer
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that would normally be considered usable.  If it returns nil,
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that buffer is rejected."
  (and (buffer-name buffer)		;First make sure it's live.
       (not (and avoid-current (eq buffer (current-buffer))))
       (with-current-buffer buffer
	 (if next-error-function   ; This is the normal test.
	     ;; Optionally reject some buffers.
	     (if extra-test-exclusive
		 (funcall extra-test-exclusive)
	       t)
	   ;; Optionally accept some other buffers.
	   (and extra-test-inclusive
		(funcall extra-test-inclusive))))))

(defun next-error-find-buffer (&optional avoid-current
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					 extra-test-inclusive
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					 extra-test-exclusive)
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  "Return a `next-error' capable buffer.
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If AVOID-CURRENT is non-nil, treat the current buffer
as an absolute last resort only.

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The function EXTRA-TEST-INCLUSIVE, if non-nil, is called in each buffer
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that normally would not qualify.  If it returns t, the buffer
in question is treated as usable.

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The function EXTRA-TEST-EXCLUSIVE, if non-nil, is called in each buffer
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that would normally be considered usable.  If it returns nil,
that buffer is rejected."
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  (or
   ;; 1. If one window on the selected frame displays such buffer, return it.
   (let ((window-buffers
          (delete-dups
           (delq nil (mapcar (lambda (w)
                               (if (next-error-buffer-p
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				    (window-buffer w)
                                    avoid-current
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                                    extra-test-inclusive extra-test-exclusive)
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                                   (window-buffer w)))
                             (window-list))))))
     (if (eq (length window-buffers) 1)
         (car window-buffers)))
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   ;; 2. If next-error-last-buffer is an acceptable buffer, use that.
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   (if (and next-error-last-buffer
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            (next-error-buffer-p next-error-last-buffer avoid-current
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                                 extra-test-inclusive extra-test-exclusive))
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       next-error-last-buffer)
   ;; 3. If the current buffer is acceptable, choose it.
   (if (next-error-buffer-p (current-buffer) avoid-current
			    extra-test-inclusive extra-test-exclusive)
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       (current-buffer))
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   ;; 4. Look for any acceptable buffer.
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   (let ((buffers (buffer-list)))
     (while (and buffers
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                 (not (next-error-buffer-p
		       (car buffers) avoid-current
		       extra-test-inclusive extra-test-exclusive)))
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       (setq buffers (cdr buffers)))
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     (car buffers))
   ;; 5. Use the current buffer as a last resort if it qualifies,
   ;; even despite AVOID-CURRENT.
   (and avoid-current
	(next-error-buffer-p (current-buffer) nil
			     extra-test-inclusive extra-test-exclusive)
	(progn
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	  (message "This is the only buffer with error message locations")
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	  (current-buffer)))
   ;; 6. Give up.
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   (error "No buffers contain error message locations")))
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(defun next-error (&optional arg reset)
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  "Visit next `next-error' message and corresponding source code.
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If all the error messages parsed so far have been processed already,
the message buffer is checked for new ones.

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A prefix ARG specifies how many error messages to move;
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negative means move back to previous error messages.
Just \\[universal-argument] as a prefix means reparse the error message buffer
and start at the first error.

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The RESET argument specifies that we should restart from the beginning.
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\\[next-error] normally uses the most recently started
compilation, grep, or occur buffer.  It can also operate on any
buffer with output from the \\[compile], \\[grep] commands, or,
more generally, on any buffer in Compilation mode or with
Compilation Minor mode enabled, or any buffer in which
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`next-error-function' is bound to an appropriate function.
To specify use of a particular buffer for error messages, type
\\[next-error] in that buffer when it is the only one displayed
in the current frame.
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Once \\[next-error] has chosen the buffer for error messages, it
runs `next-error-hook' with `run-hooks', and stays with that buffer
until you use it in some other buffer which uses Compilation mode
or Compilation Minor mode.
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To control which errors are matched, customize the variable
`compilation-error-regexp-alist'."
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  (interactive "P")
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  (if (consp arg) (setq reset t arg nil))
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  (when (setq next-error-last-buffer (next-error-find-buffer))
    ;; we know here that next-error-function is a valid symbol we can funcall
    (with-current-buffer next-error-last-buffer
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      (funcall next-error-function (prefix-numeric-value arg) reset)
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      (when next-error-recenter
        (recenter next-error-recenter))
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      (run-hooks 'next-error-hook))))
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(defun next-error-internal ()
  "Visit the source code corresponding to the `next-error' message at point."
  (setq next-error-last-buffer (current-buffer))
  ;; we know here that next-error-function is a valid symbol we can funcall
  (with-current-buffer next-error-last-buffer
    (funcall next-error-function 0 nil)
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    (when next-error-recenter
      (recenter next-error-recenter))
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    (run-hooks 'next-error-hook)))

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(defalias 'goto-next-locus 'next-error)
(defalias 'next-match 'next-error)

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(defun previous-error (&optional n)
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  "Visit previous `next-error' message and corresponding source code.
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Prefix arg N says how many error messages to move backwards (or
forwards, if negative).

This operates on the output from the \\[compile] and \\[grep] commands."
  (interactive "p")
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  (next-error (- (or n 1))))
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(defun first-error (&optional n)
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  "Restart at the first error.
Visit corresponding source code.
With prefix arg N, visit the source code of the Nth error.
This operates on the output from the \\[compile] command, for instance."
  (interactive "p")
  (next-error n t))

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(defun next-error-no-select (&optional n)
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  "Move point to the next error in the `next-error' buffer and highlight match.
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Prefix arg N says how many error messages to move forwards (or
backwards, if negative).
Finds and highlights the source line like \\[next-error], but does not
select the source buffer."
  (interactive "p")
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  (let ((next-error-highlight next-error-highlight-no-select))
    (next-error n))
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  (pop-to-buffer next-error-last-buffer))

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(defun previous-error-no-select (&optional n)
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  "Move point to the previous error in the `next-error' buffer and highlight match.
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Prefix arg N says how many error messages to move backwards (or
forwards, if negative).
Finds and highlights the source line like \\[previous-error], but does not
select the source buffer."
  (interactive "p")
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  (next-error-no-select (- (or n 1))))
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;; Internal variable for `next-error-follow-mode-post-command-hook'.
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(defvar next-error-follow-last-line nil)

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(define-minor-mode next-error-follow-minor-mode
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  "Minor mode for compilation, occur and diff modes.
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With a prefix argument ARG, enable mode if ARG is positive, and
disable it otherwise.  If called from Lisp, enable mode if ARG is
omitted or nil.
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When turned on, cursor motion in the compilation, grep, occur or diff
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buffer causes automatic display of the corresponding source code location."
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  :group 'next-error :init-value nil :lighter " Fol"
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  (if (not next-error-follow-minor-mode)
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      (remove-hook 'post-command-hook 'next-error-follow-mode-post-command-hook t)
    (add-hook 'post-command-hook 'next-error-follow-mode-post-command-hook nil t)
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    (make-local-variable 'next-error-follow-last-line)))
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;; Used as a `post-command-hook' by `next-error-follow-mode'
;; for the *Compilation* *grep* and *Occur* buffers.
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(defun next-error-follow-mode-post-command-hook ()
  (unless (equal next-error-follow-last-line (line-number-at-pos))
    (setq next-error-follow-last-line (line-number-at-pos))
    (condition-case nil
	(let ((compilation-context-lines nil))
	  (setq compilation-current-error (point))
	  (next-error-no-select 0))
      (error t))))

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;;;

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(defun fundamental-mode ()
  "Major mode not specialized for anything in particular.
Other major modes are defined by comparison with this one."
  (interactive)
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  (kill-all-local-variables)
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  (run-mode-hooks))
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;; Special major modes to view specially formatted data rather than files.

(defvar special-mode-map
  (let ((map (make-sparse-keymap)))
    (suppress-keymap map)
    (define-key map "q" 'quit-window)
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    (define-key map " " 'scroll-up-command)
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    (define-key map [?\S-\ ] 'scroll-down-command)
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    (define-key map "\C-?" 'scroll-down-command)
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    (define-key map "?" 'describe-mode)
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    (define-key map "h" 'describe-mode)
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    (define-key map ">" 'end-of-buffer)
    (define-key map "<" 'beginning-of-buffer)
    (define-key map "g" 'revert-buffer)
    map))
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(put 'special-mode 'mode-class 'special)
(define-derived-mode special-mode nil "Special"
  "Parent major mode from which special major modes should inherit."
  (setq buffer-read-only t))

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;; Making and deleting lines.

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(defvar self-insert-uses-region-functions nil
  "Special hook to tell if `self-insert-command' will use the region.
It must be called via `run-hook-with-args-until-success' with no arguments.
Any `post-self-insert-command' which consumes the region should
register a function on this hook so that things like `delete-selection-mode'
can refrain from consuming the region.")

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(defvar hard-newline (propertize "\n" 'hard t 'rear-nonsticky '(hard))
  "Propertized string representing a hard newline character.")
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(defun newline (&optional arg interactive)
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  "Insert a newline, and move to left margin of the new line if it's blank.
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If option `use-hard-newlines' is non-nil, the newline is marked with the
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text-property `hard'.
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With ARG, insert that many newlines.
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If `electric-indent-mode' is enabled, this indents the final new line
that it adds, and reindents the preceding line.  To just insert
a newline, use \\[electric-indent-just-newline].
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Calls `auto-fill-function' if the current column number is greater
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than the value of `fill-column' and ARG is nil.
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A non-nil INTERACTIVE argument means to run the `post-self-insert-hook'."
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  (interactive "*P\np")
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  (barf-if-buffer-read-only)
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  ;; Call self-insert so that auto-fill, abbrev expansion etc. happens.
  ;; Set last-command-event to tell self-insert what to insert.
  (let* ((was-page-start (and (bolp) (looking-at page-delimiter)))
         (beforepos (point))
         (last-command-event ?\n)
         ;; Don't auto-fill if we have a numeric argument.
         (auto-fill-function (if arg nil auto-fill-function))
         (postproc
          ;; Do the rest in post-self-insert-hook, because we want to do it
          ;; *before* other functions on that hook.
          (lambda ()
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            (cl-assert (eq ?\n (char-before)))
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            ;; Mark the newline(s) `hard'.
            (if use-hard-newlines
                (set-hard-newline-properties
                 (- (point) (prefix-numeric-value arg)) (point)))
            ;; If the newline leaves the previous line blank, and we
            ;; have a left margin, delete that from the blank line.
            (save-excursion
              (goto-char beforepos)
              (beginning-of-line)
              (and (looking-at "[ \t]$")
                   (> (current-left-margin) 0)
                   (delete-region (point)
                                  (line-end-position))))
            ;; Indent the line after the newline, except in one case:
            ;; when we added the newline at the beginning of a line which
            ;; starts a page.
            (or was-page-start
                (move-to-left-margin nil t)))))
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    (unwind-protect
        (if (not interactive)
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        ;; FIXME: For non-interactive uses, many calls actually just want
        ;; (insert "\n"), so maybe we should do just that, so as to avoid
        ;; the risk of filling or running abbrevs unexpectedly.
        (let ((post-self-insert-hook (list postproc)))
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          (self-insert-command (prefix-numeric-value arg)))
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      (unwind-protect
          (progn
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            (add-hook 'post-self-insert-hook postproc nil t)
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            (self-insert-command (prefix-numeric-value arg)))
        ;; We first used let-binding to protect the hook, but that was naive
        ;; since add-hook affects the symbol-default value of the variable,
        ;; whereas the let-binding might only protect the buffer-local value.
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        (remove-hook 'post-self-insert-hook postproc t)))
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      (cl-assert (not (member postproc post-self-insert-hook)))
      (cl-assert (not (member postproc (default-value 'post-self-insert-hook))))))
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  nil)

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(defun set-hard-newline-properties (from to)
  (let ((sticky (get-text-property from 'rear-nonsticky)))
    (put-text-property from to 'hard 't)
    ;; If rear-nonsticky is not "t", add 'hard to rear-nonsticky list
    (if (and (listp sticky) (not (memq 'hard sticky)))
	(put-text-property from (point) 'rear-nonsticky
			   (cons 'hard sticky)))))
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(defun open-line (n)
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  "Insert a newline and leave point before it.
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If there is a fill prefix and/or a `left-margin', insert them
on the new line if the line would have been blank.
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With arg N, insert N newlines."
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  (interactive "*p")
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  (let* ((do-fill-prefix (and fill-prefix (bolp)))
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	 (do-left-margin (and (bolp) (> (current-left-margin) 0)))
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	 (loc (point-marker))
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	 ;; Don't expand an abbrev before point.
	 (abbrev-mode nil))
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    (newline n)
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    (goto-char loc)
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    (while (> n 0)
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      (cond ((bolp)
	     (if do-left-margin (indent-to (current-left-margin)))
	     (if do-fill-prefix (insert-and-inherit fill-prefix))))
      (forward-line 1)
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      (setq n (1- n)))
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    (goto-char loc)
    (end-of-line)))
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(defun split-line (&optional arg)
  "Split current line, moving portion beyond point vertically down.
If the current line starts with `fill-prefix', insert it on the new
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line as well.  With prefix ARG, don't insert `fill-prefix' on new line.
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When called from Lisp code, ARG may be a prefix string to copy."
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  (interactive "*P")
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  (skip-chars-forward " \t")
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  (let* ((col (current-column))
	 (pos (point))
	 ;; What prefix should we check for (nil means don't).
	 (prefix (cond ((stringp arg) arg)
		       (arg nil)
		       (t fill-prefix)))
	 ;; Does this line start with it?
	 (have-prfx (and prefix
			 (save-excursion
			   (beginning-of-line)
			   (looking-at (regexp-quote prefix))))))
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    (newline 1)
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    (if have-prfx (insert-and-inherit prefix))
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    (indent-to col 0)
    (goto-char pos)))

(defun delete-indentation (&optional arg)
  "Join this line to previous and fix up whitespace at join.
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If there is a fill prefix, delete it from the beginning of this line.
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With argument, join this line to following line."
  (interactive "*P")
  (beginning-of-line)
  (if arg (forward-line 1))
  (if (eq (preceding-char) ?\n)
      (progn
	(delete-region (point) (1- (point)))
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	;; If the second line started with the fill prefix,
	;; delete the prefix.
	(if (and fill-prefix
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		 (<= (+ (point) (length fill-prefix)) (point-max))
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		 (string= fill-prefix
			  (buffer-substring (point)
					    (+ (point) (length fill-prefix)))))
	    (delete-region (point) (+ (point) (length fill-prefix))))
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	(fixup-whitespace))))

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(defalias 'join-line #'delete-indentation) ; easier to find
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(defun delete-blank-lines ()
  "On blank line, delete all surrounding blank lines, leaving just one.
On isolated blank line, delete that one.
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On nonblank line, delete any immediately following blank lines."
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  (interactive "*")
  (let (thisblank singleblank)
    (save-excursion
      (beginning-of-line)
      (setq thisblank (looking-at "[ \t]*$"))
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      ;; Set singleblank if there is just one blank line here.
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      (setq singleblank
	    (and thisblank
		 (not (looking-at "[ \t]*\n[ \t]*$"))
		 (or (bobp)
		     (progn (forward-line -1)
			    (not (looking-at "[ \t]*$")))))))
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    ;; Delete preceding blank lines, and this one too if it's the only one.
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    (if thisblank
	(progn
	  (beginning-of-line)
	  (if singleblank (forward-line 1))
	  (delete-region (point)
			 (if (re-search-backward "[^ \t\n]" nil t)
			     (progn (forward-line 1) (point))
			   (point-min)))))
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    ;; Delete following blank lines, unless the current line is blank
    ;; and there are no following blank lines.
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    (if (not (and thisblank singleblank))
	(save-excursion
	  (end-of-line)
	  (forward-line 1)
	  (delete-region (point)
			 (if (re-search-forward "[^ \t\n]" nil t)
			     (progn (beginning-of-line) (point))
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			   (point-max)))))
    ;; Handle the special case where point is followed by newline and eob.
    ;; Delete the line, leaving point at eob.
    (if (looking-at "^[ \t]*\n\\'")
	(delete-region (point) (point-max)))))
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(defcustom delete-trailing-lines t
  "If non-nil, \\[delete-trailing-whitespace] deletes trailing lines.
Trailing lines are deleted only if `delete-trailing-whitespace'
is called on the entire buffer (rather than an active region)."
  :type 'boolean
  :group 'editing
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  :version "24.3")
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(defun delete-trailing-whitespace (&optional start end)
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  "Delete trailing whitespace between START and END.
If called interactively, START and END are the start/end of the
region if the mark is active, or of the buffer's accessible
portion if the mark is inactive.

This command deletes whitespace characters after the last
non-whitespace character in each line between START and END.  It
does not consider formfeed characters to be whitespace.

If this command acts on the entire buffer (i.e. if called
interactively with the mark inactive, or called from Lisp with
END nil), it also deletes all trailing lines at the end of the
buffer if the variable `delete-trailing-lines' is non-nil."
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  (interactive (progn
                 (barf-if-buffer-read-only)
                 (if (use-region-p)
                     (list (region-beginning) (region-end))
                   (list nil nil))))
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  (save-match-data
    (save-excursion
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      (let ((end-marker (copy-marker (or end (point-max))))
            (start (or start (point-min))))
        (goto-char start)
        (while (re-search-forward "\\s-$" end-marker t)
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          (skip-syntax-backward "-" (line-beginning-position))
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          ;; Don't delete formfeeds, even if they are considered whitespace.
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          (if (looking-at-p ".*\f")
              (goto-char (match-end 0)))
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          (delete-region (point) (match-end 0)))
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        ;; Delete trailing empty lines.
        (goto-char end-marker)
        (when (and (not end)
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		   delete-trailing-lines
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                   ;; Really the end of buffer.
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		   (= (point-max) (1+ (buffer-size)))
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                   (<= (skip-chars-backward "\n") -2))
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          (delete-region (1+ (point)) end-marker))
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        (set-marker end-marker nil))))
  ;; Return nil for the benefit of `write-file-functions'.
  nil)
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(defun newline-and-indent ()
  "Insert a newline, then indent according to major mode.
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Indentation is done using the value of `indent-line-function'.
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In programming language modes, this is the same as TAB.
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In some text modes, where TAB inserts a tab, this command indents to the
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column specified by the function `current-left-margin'."
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  (interactive "*")
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  (delete-horizontal-space t)
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  (newline nil t)
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  (indent-according-to-mode))

(defun reindent-then-newline-and-indent ()
  "Reindent current line, insert newline, then indent the new line.
Indentation of both lines is done according to the current major mode,
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which means calling the current value of `indent-line-function'.
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In programming language modes, this is the same as TAB.
In some text modes, where TAB inserts a tab, this indents to the
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column specified by the function `current-left-margin'."
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  (interactive "*")
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  (let ((pos (point)))
    ;; Be careful to insert the newline before indenting the line.
    ;; Otherwise, the indentation might be wrong.
    (newline)
    (save-excursion
      (goto-char pos)
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      ;; We are at EOL before the call to indent-according-to-mode, and
      ;; after it we usually are as well, but not always.  We tried to
      ;; address it with `save-excursion' but that uses a normal marker
      ;; whereas we need `move after insertion', so we do the save/restore
      ;; by hand.
      (setq pos (copy-marker pos t))
      (indent-according-to-mode)
      (goto-char pos)
      ;; Remove the trailing white-space after indentation because
      ;; indentation may introduce the whitespace.
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      (delete-horizontal-space t))
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    (indent-according-to-mode)))
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(defcustom read-quoted-char-radix 8
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  "Radix for \\[quoted-insert] and other uses of `read-quoted-char'.
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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."
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  (let ((message-log-max nil)
	(help-events (delq nil (mapcar (lambda (c) (unless (characterp c) c))
				       help-event-list)))
	done (first t) (code 0) translated)
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    (while (not done)
      (let ((inhibit-quit first)
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	    ;; Don't let C-h or other help chars get the help
	    ;; message--only help function keys.  See bug#16617.
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	    (help-char nil)
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	    (help-event-list help-events)
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	    (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 translated (read-key (and prompt (format "%s-" prompt))))
	(if inhibit-quit (setq quit-flag nil)))
      (if (integerp translated)
	  (setq translated (char-resolve-modifiers translated)))
      (cond ((null translated))
	    ((not (integerp translated))
	     (setq unread-command-events
                   (listify-key-sequence (this-single-command-raw-keys))
		   done t))
	    ((/= (logand translated ?\M-\^@) 0)
	     ;; Turn a meta-character into a character with the 0200 bit set.
	     (setq code (logior (logand translated (lognot ?\M-\^@)) 128)
		   done t))
	    ((and (<= ?0 translated)
                  (< translated (+ ?0 (min 10 read-quoted-char-radix))))
	     (setq code (+ (* code read-quoted-char-radix) (- translated ?0)))
	     (and prompt (setq prompt (message "%s %c" prompt translated))))
	    ((and (<= ?a (downcase translated))
		  (< (downcase translated)
                     (+ ?a -10 (min 36 read-quoted-char-radix))))
	     (setq code (+ (* code read-quoted-char-radix)
			   (+ 10 (- (downcase translated) ?a))))
	     (and prompt (setq prompt (message "%s %c" prompt translated))))
	    ((and (not first) (eq translated ?\C-m))
	     (setq done t))
	    ((not first)
	     (setq unread-command-events
                   (listify-key-sequence (this-single-command-raw-keys))
		   done t))
	    (t (setq code translated
		     done t)))
      (setq first nil))
    code))

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(defun quoted-insert (arg)
  "Read next input character and insert it.
This is useful for inserting control characters.
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With argument, insert ARG copies of the character.
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If the first character you type after this command is an octal digit,
you should type a sequence of octal digits which specify a character code.
Any nondigit terminates the sequence.  If the terminator is a RET,
it is discarded; any other terminator is used itself as input.
The variable `read-quoted-char-radix' specifies the radix for this feature;
set it to 10 or 16 to use decimal or hex instead of octal.
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In overwrite mode, this function inserts the character anyway, and
does not handle octal digits specially.  This means that if you use
overwrite as your normal editing mode, you can use this function to
insert characters when necessary.
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In binary overwrite mode, this function does overwrite, and octal
digits are interpreted as a character code.  This is intended to be
useful for editing binary files."
  (interactive "*p")
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  (let* ((char
	  ;; Avoid "obsolete" warnings for translation-table-for-input.
	  (with-no-warnings
	    (let (translation-table-for-input input-method-function)
	      (if (or (not overwrite-mode)
		      (eq overwrite-mode 'overwrite-mode-binary))
		  (read-quoted-char)
		(read-char))))))
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    ;; This used to assume character codes 0240 - 0377 stand for
    ;; characters in some single-byte character set, and converted them
    ;; to Emacs characters.  But in 23.1 this feature is deprecated
    ;; in favor of inserting the corresponding Unicode characters.
    ;; (if (and enable-multibyte-characters
    ;;          (>= char ?\240)
    ;;          (<= char ?\377))
    ;;     (setq char (unibyte-char-to-multibyte char)))
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    (unless (characterp char)
      (user-error "%s is not a valid character"
		  (key-description (vector char))))
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    (if (> arg 0)
	(if (eq overwrite-mode 'overwrite-mode-binary)
	    (delete-char arg)))
    (while (> arg 0)
      (insert-and-inherit char)
      (setq arg (1- arg)))))
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(defun forward-to-indentation (&optional arg)
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  "Move forward ARG lines and position at first nonblank character."
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  (interactive "^p")
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  (forward-line (or arg 1))
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  (skip-chars-forward " \t"))
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(defun backward-to-indentation (&optional arg)
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  "Move backward ARG lines and position at first nonblank character."
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  (interactive "^p")
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  (forward-line (- (or arg 1)))
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  (skip-chars-forward " \t"))
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(defun back-to-indentation ()
  "Move point to the first non-whitespace character on this line."
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  (interactive "^")
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  (beginning-of-line 1)
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  (skip-syntax-forward " " (line-end-position))
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  ;; Move back over chars that have whitespace syntax but have the p flag.
  (backward-prefix-chars))
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(defun fixup-whitespace ()
  "Fixup white space between objects around point.
Leave one space or none, according to the context."
  (interactive "*")
  (save-excursion
    (delete-horizontal-space)
    (if (or (looking-at "^\\|\\s)")
	    (save-excursion (forward-char -1)
			    (looking-at "$\\|\\s(\\|\\s'")))
	nil
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      (insert ?\s))))
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(defun delete-horizontal-space (&optional backward-only)
  "Delete all spaces and tabs around point.
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If BACKWARD-ONLY is non-nil, only delete them before point."
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  (interactive "*P")
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  (let ((orig-pos (point)))
    (delete-region
     (if backward-only
	 orig-pos
       (progn
	 (skip-chars-forward " \t")
	 (constrain-to-field nil orig-pos t)))
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     (progn
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       (skip-chars-backward " \t")
       (constrain-to-field nil orig-pos)))))
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(defun just-one-space (&optional n)
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  "Delete all spaces and tabs around point, leaving one space (or N spaces).
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If N is negative, delete newlines as well, leaving -N spaces.
See also `cycle-spacing'."
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  (interactive "*p")
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  (cycle-spacing n nil 'single-shot))
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(defvar cycle-spacing--context nil
  "Store context used in consecutive calls to `cycle-spacing' command.
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The first time `cycle-spacing' runs, it saves in this variable:
its N argument, the original point position, and the original spacing
around point.")
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(defun cycle-spacing (&optional n preserve-nl-back mode)
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  "Manipulate whitespace around point in a smart way.
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In interactive use, this function behaves differently in successive
consecutive calls.
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The first call in a sequence acts like `just-one-space'.
It deletes all spaces and tabs around point, leaving one space
\(or N spaces).  N is the prefix argument.  If N is negative,
it deletes newlines as well, leaving -N spaces.
\(If PRESERVE-NL-BACK is non-nil, it does not delete newlines before point.)
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The second call in a sequence deletes all spaces.
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The third call in a sequence restores the original whitespace (and point).
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If MODE is `single-shot', it only performs the first step in the sequence.
If MODE is `fast' and the first step would not result in any change
\(i.e., there are exactly (abs N) spaces around point),
the function goes straight to the second step.
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Repeatedly calling the function with different values of N starts a
new sequence each time."
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  (interactive "*p")
  (let ((orig-pos	 (point))
	(skip-characters (if (and n (< n 0)) " \t\n\r" " \t"))
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	(num		 (abs (or n 1))))
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    (skip-chars-backward (if preserve-nl-back " \t" skip-characters))
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    (constrain-to-field nil orig-pos)
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    (cond
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     ;; Command run for the first time, single-shot mode or different argument
     ((or (eq 'single-shot mode)
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	  (not (equal last-command this-command))
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	  (not cycle-spacing--context)
	  (not (eq (car cycle-spacing--context) n)))
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      (let* ((start (point))
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	     (num   (- num (skip-chars-forward " " (+ num (point)))))
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	     (mid   (point))
	     (end   (progn
		      (skip-chars-forward skip-characters)
		      (constrain-to-field nil orig-pos t))))
	(setq cycle-spacing--context  ;; Save for later.
	      ;; Special handling for case where there was no space at all.
	      (unless (= start end)
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                (cons n (cons orig-pos (buffer-substring start (point))))))
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	;; If this run causes no change in buffer content, delete all spaces,
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	;; otherwise delete all excess spaces.
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	(delete-region (if (and (eq mode 'fast) (zerop num) (= mid end))
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			   start mid) end)
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        (insert (make-string num ?\s))))
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     ;; Command run for the second time.
     ((not (equal orig-pos (point)))
      (delete-region (point) orig-pos))

     ;; Command run for the third time.
     (t
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