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[gnu-emacs] / lisp / international / mule.el

diff --git a/lisp/international/mule.el b/lisp/international/mule.el
index 1de2d5106e397d926b5d6bb0647d627d3b903054..60a90ae15a4874e0ed7a84e389a398d8d61d81c6 100644 (file)
--- a/lisp/international/mule.el
+++ b/lisp/international/mule.el
@@ -1,6 +1,6 @@
 ;;; mule.el --- basic commands for multilingual environment
 
-;; Copyright (C) 1997-2015 Free Software Foundation, Inc.
+;; Copyright (C) 1997-2016 Free Software Foundation, Inc.
 ;; Copyright (C) 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
 ;;   2005, 2006, 2007, 2008, 2009, 2010, 2011
 ;;   National Institute of Advanced Industrial Science and Technology (AIST)
@@ -665,8 +665,8 @@ without any conversions.
 
 VALUE is the EOL (end-of-line) format of the coding system.  It must be
 one of `unix', `dos', `mac'.  The symbol `unix' means Unix-like EOL
-\(i.e. a single LF character), `dos' means DOS-like EOL \(i.e. a sequence
-of CR followed by LF), and `mac' means Mac-like EOL \(i.e. a single CR).
+\(i.e., a single LF character), `dos' means DOS-like EOL \(i.e., a sequence
+of CR followed by LF), and `mac' means Mac-like EOL \(i.e., a single CR).
 If omitted, Emacs detects the EOL format automatically when decoding.
 
 `:charset-list' (required if `:coding-type' is `charset' or `shift-jis')
@@ -2002,7 +2002,7 @@ use \"coding: 'raw-text\" instead."
                (goto-char pos)
                (when (and set-auto-coding-for-load
                           (re-search-forward re-unibyte tail-end t))
-                  (display-warning 'mule "`unibyte: t' is obsolete; \
+                  (display-warning 'mule "\"unibyte: t\" is obsolete; \
 use \"coding: 'raw-text\" instead." :warning)
                  (setq coding-system 'raw-text))
                (when (and (not coding-system)
@@ -2317,7 +2317,13 @@ ALIST is an alist, each element has the form (FROM . TO).
 FROM and TO are a character or a vector of characters.
 If FROM is a character, that character is translated to TO.
 If FROM is a vector of characters, that sequence is translated to TO.
-The first extra-slot of the value is a translation table for reverse mapping."
+The first extra-slot of the value is a translation table for reverse mapping.
+
+FROM and TO may be nil.  If TO is nil, the translation from FROM
+to nothing is defined in the translation table and that element
+is ignored in the reverse map.  If FROM is nil, the translation
+from TO to nothing is defined in the reverse map only.  A vector
+of length zero has the same meaning as specifying nil."
   (let ((tables (vector (make-char-table 'translation-table)
                        (make-char-table 'translation-table)))
        table max-lookup from to idx val)
@@ -2330,20 +2336,23 @@ The first extra-slot of the value is a translation table for reverse mapping."
          (setq from (cdr elt) to (car elt)))
        (if (characterp from)
            (setq idx from)
-         (setq idx (aref from 0)
-               max-lookup (max max-lookup (length from))))
-       (setq val (aref table idx))
-       (if val
-           (progn
-             (or (consp val)
-                 (setq val (list (cons (vector idx) val))))
-             (if (characterp from)
-                 (setq from (vector from)))
-             (setq val (nconc val (list (cons from to)))))
-         (if (characterp from)
-             (setq val to)
-           (setq val (list (cons from to)))))
-       (aset table idx val))
+         (if (= (length from) 0)
+             (setq idx nil)
+           (setq idx (aref from 0)
+                 max-lookup (max max-lookup (length from)))))
+       (when idx
+         (setq val (aref table idx))
+         (if val
+             (progn
+               (or (consp val)
+                   (setq val (list (cons (vector idx) val))))
+               (if (characterp from)
+                   (setq from (vector from)))
+               (setq val (nconc val (list (cons from to)))))
+           (if (characterp from)
+               (setq val to)
+             (setq val (list (cons from to)))))
+         (aset table idx val)))
       (set-char-table-extra-slot table 1 max-lookup))
     (set-char-table-extra-slot (aref tables 0) 0 (aref tables 1))
     (aref tables 0)))