lisp/tabify.el

   1 ;;; tabify.el --- tab conversion commands for Emacs
   2
   3 ;; Copyright (C) 1985, 1994 Free Software Foundation, Inc.
   4
   5 ;; Maintainer: FSF
   6
   7 ;; This file is part of GNU Emacs.
   8
   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.
  13
  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.
  18
  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.
  23
  24 ;;; Commentary:
  25
  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.
  28
  29 ;;; Code:
  30
  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))))))
  51
  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.")
  56
  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))))))
  79
  80 (provide 'tabify)
  81
  82 ;;; tabify.el ends here