(EXT:CHAR-INVERTCASE char) returns the corresponding character in the other case for CHAR, i.e., CHAR-UPCASE for a lowercase character and CHAR-DOWNCASE for an uppercase character; for a character that does not have a case attribute, the argument is returned. See also EXT:STRING-INVERTCASE and EXT:NSTRING-INVERTCASE.

The characters with case are those UNICODE characters c, for which the upper case mapping uc and the lower case mapping lc have the following properties:

The titlecase property of UNICODE characters has no equivalent in Common Lisp.