• char-upcase character → corresponding-character
• char-downcase character → corresponding-character

• character, corresponding-character - a character.

If character is a lowercase character, char-upcase returns the corresponding uppercase character. Otherwise, char-upcase just returns the given character.

If character is an uppercase character, char-downcase returns the corresponding lowercase character. Otherwise, char-downcase just returns the given character.

The result only ever differs from character in its code attribute; all implementation-defined attributes are preserved.

(char-upcase #\a) 

→

#\A 



(char-upcase #\A) 

→

#\A 



(char-downcase #\a) 

→

#\a 



(char-downcase #\A) 

→

#\a 



(char-upcase #\9) 

→

#\9 



(char-downcase #\9) 

→

#\9 



(char-upcase #\@) 

→

#\@ 



(char-downcase #\@) 

→

#\@ 

Note that this next example might run for a very long time in some implementations if char-code-limit happens to be very large for that implementation.

(dotimes (code char-code-limit)
  (let ((char (code-char code)))
    (when char
      (unless (cond ((upper-case-p char) 
                     (char= (char-upcase (char-downcase char)) char))
                    ((lower-case-p char) 
                     (char= (char-downcase (char-upcase char)) char))
                    (t
                     (and (char= (char-upcase (char-downcase char)) char) 
                          (char= (char-downcase (char-upcase char)) char)))) 
        (return char))))) 

→

NIL ;; TODO fix, does not return NIL on SBCL, ECL or CMUCL

None.

Should signal an error of type type-error if character is not a character.

Function UPPER-CASE-P, Function ALPHA-CHAR-P, {\secref\CharactersWithCase}, {\secref\ImplementationDefinedScripts}

If the corresponding-char is different than character, then both the character and the corresponding-char have case.

Since char-equal ignores the case of the characters it compares, the corresponding-character is always the same as character under char-equal.

\issue{CHARACTER-PROPOSAL:2-1-1}