Merge branch 'master' of git.sv.gnu.org:/srv/git/emacs.

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

diff --git a/lisp/international/mule.el b/lisp/international/mule.el
index c957a77e9ab776d6e36a496c28c1b20ad1f3f301..392ecff021a9cf9e79d1428c66d1934885461883 100644 (file)
--- a/lisp/international/mule.el
+++ b/lisp/international/mule.el
@@ -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)))