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+;;; mule-caesar.el --- ROT 13-47 Caesar rotation utility
+
+;; Copyright (C) 1997 Free Software Foundation, Inc.
+
+;; Author: MORIOKA Tomohiko <morioka@jaist.ac.jp>
+;; Version: $Id: mule-caesar.el,v 1.1 1997-05-09 01:22:58 morioka Exp $
+;; Keywords: ROT 13-47, caesar, mail, news, text/x-rot13-47
+
+;; This file is part of APEL (A Portable Emacs Library).
+
+;; This program is free software; you can redistribute it and/or
+;; modify it under the terms of the GNU General Public License as
+;; published by the Free Software Foundation; either version 2, or (at
+;; your option) any later version.
+
+;; This program is distributed in the hope that it will be useful, but
+;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;; General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs; see the file COPYING.  If not, write to the
+;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+;; Boston, MA 02111-1307, USA.
+
+;;; Commentary:
+
+;; Thanks for Martin Buchholz <mrb@eng.sun.com>'s suggestion
+
+;;; Code:
+
+(defun mule-caesar-string (string &optional stride-ascii)
+  "Caesar rotation of STRING, and return the result.
+Optional argument STRIDE-ASCII is rotation-size for Latin alphabet
+\(A-Z and a-z).  For non-ASCII text, ROT47 will be performed in any
+case."
+  (setq stride-ascii
+       (if stride-ascii
+           (mod stride-ascii 26)
+         13))
+  (mapconcat (function
+             (lambda (chr)
+               (if (< chr 128)
+                   (cond ((and (<= ?A chr) (<= chr ?Z))
+                          (setq chr (+ chr stride-ascii))
+                          (if (> chr ?Z)
+                              (setq chr (- chr 26))
+                            ))
+                         ((and (<= ?a chr) (<= chr ?z))
+                          (setq chr (+ chr stride-ascii))
+                          (if (> chr ?z)
+                              (setq chr (- chr 26))
+                            )))
+                 (let ((octet (logand chr 127)))
+                   (if (and (< 32 octet) (< octet 127))
+                       (setq chr
+                             (if (< octet 80)
+                                 (+ chr 47)
+                               (- chr 47)))
+                     )))
+               (char-to-string chr)
+               )) string "")
+  )
+
+(defun mule-caesar-region (start end stride-ascii)
+  "Caesar rotation of current region.
+Optional argument STRIDE-ASCII is rotation-size for Latin alphabet
+\(A-Z and a-z).  For non-ASCII text, ROT47 will be performed in any
+case."
+  (interactive "r\nP")
+  (save-excursion
+    (let ((str (buffer-substring start end)))
+      (delete-region start end)
+      (insert (mule-caesar-string str stride-ascii))
+      )))
+
+
+(provide 'mule-caesar)
+
+;;; mule-caesar.el ends here