char-upcase character => corresponding-character
char-downcase character => corresponding-character
Arguments and Values:
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
Affected By: None.
Should signal an error of type type-error if character is not a character.
upper-case-p, alpha-char-p, Section 22.214.171.124 (Characters With Case), Section 13.1.10 (Documentation of Implementation-Defined Scripts)
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.