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[emacs.git] / lisp / tabify.el
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1 ;;; tabify.el --- tab conversion commands for Emacs
3 ;; Copyright (C) 1985, 1994 Free Software Foundation, Inc.
5 ;; Maintainer: FSF
7 ;; This file is part of GNU Emacs.
9 ;; GNU Emacs is free software; you can redistribute it and/or modify
10 ;; it under the terms of the GNU General Public License as published by
11 ;; the Free Software Foundation; either version 2, or (at your option)
12 ;; any later version.
14 ;; GNU Emacs is distributed in the hope that it will be useful,
15 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
16 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 ;; GNU General Public License for more details.
19 ;; You should have received a copy of the GNU General Public License
20 ;; along with GNU Emacs; see the file COPYING. If not, write to the
21 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
22 ;; Boston, MA 02111-1307, USA.
24 ;;; Commentary:
26 ;; Commands to optimize spaces to tabs or expand tabs to spaces in a region
27 ;; (`tabify' and `untabify'). The variable tab-width does the obvious.
29 ;;; Code:
31 ;;;###autoload
32 (defun untabify (start end)
33 "Convert all tabs in region to multiple spaces, preserving columns.
34 Called non-interactively, the region is specified by arguments
35 START and END, rather than by the position of point and mark.
36 The variable `tab-width' controls the spacing of tab stops."
37 (interactive "r")
38 (save-excursion
39 (save-restriction
40 (narrow-to-region (point-min) end)
41 (goto-char start)
42 (while (search-forward "\t" nil t) ; faster than re-search
43 (forward-char -1)
44 (let ((tab-beg (point))
45 (indent-tabs-mode nil)
46 column)
47 (skip-chars-forward "\t")
48 (setq column (current-column))
49 (delete-region tab-beg (point))
50 (indent-to column))))))
52 (defvar tabify-regexp "[ \t][ \t]+"
53 "Regexp matching whitespace that tabify should consider.
54 Usually this will be \"[ \\t][ \\t]+\" to match two or more spaces or tabs.
55 \"^[ \\t]+\" is also useful, for tabifying only initial whitespace.")
57 ;;;###autoload
58 (defun tabify (start end)
59 "Convert multiple spaces in region to tabs when possible.
60 A group of spaces is partially replaced by tabs
61 when this can be done without changing the column they end at.
62 Called non-interactively, the region is specified by arguments
63 START and END, rather than by the position of point and mark.
64 The variable `tab-width' controls the spacing of tab stops."
65 (interactive "r")
66 (save-excursion
67 (save-restriction
68 ;; Include the beginning of the line in the narrowing
69 ;; since otherwise it will throw off current-column.
70 (goto-char start)
71 (beginning-of-line)
72 (narrow-to-region (point) end)
73 (goto-char start)
74 (while (re-search-forward tabify-regexp nil t)
75 (let ((column (current-column))
76 (indent-tabs-mode t))
77 (delete-region (match-beginning 0) (point))
78 (indent-to column))))))
80 (provide 'tabify)
82 ;;; tabify.el ends here