Add 'char-to-name' convenience function

* lisp/international/mule-cmds.el (char-to-name): New function.  This is
the inverse of 'char-from-name'.
* doc/lispref/nonascii.texi (Character Codes): Document it.
* etc/NEWS: Announce it.

doc/lispref/nonascii.texi

@@ -435,6 +435,11 @@ This function returns @code{nil} if @var{string} does not name a character.
 @end example
 @end defun
 
+@defun char-to-name char
+This function returns the Unicode name of @var{char}.  Returns
+@code{nil} if @var{char} is not a character or has no Unicode name.
+@end defun
+
 @defun get-byte &optional pos string
 This function returns the byte at character position @var{pos} in the
 current buffer.  If the current buffer is unibyte, this is literally

etc/NEWS

@@ -2244,6 +2244,10 @@ it returns a short "unique" string that identifies the function.
 In either case, the string is propertized so clicking on it gives
 further details.
 
+** New function 'char-to-name'.
+This is a convenience function to return the Unicode name of a char (if
+it has one).
+
 ** New function 'cl-type-of'.
 This function is like 'type-of' except that it sometimes returns
 a more precise type.  For example, for nil and t it returns 'null'

lisp/international/mule-cmds.el

@@ -3183,6 +3183,13 @@ on encoding."
            (script (and char (aref char-script-table char))))
       (if script (symbol-name script) "ungrouped"))))
 
+(defun char-to-name (char)
+  "Return the Unicode name for CHAR, if it has one, else nil.
+Return nil if CHAR is not a character."
+  (and (characterp char)
+       (or (get-char-code-property char 'name)
+           (get-char-code-property char 'old-name))))
+
 (defun char-from-name (string &optional ignore-case)
   "Return a character as a number from its Unicode name STRING.
 If optional IGNORE-CASE is non-nil, ignore case in STRING.