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
Should signal an error of type type-error if character is not a character.
upper-case-p; lower-case-p; both-case-p, alpha-char-p, Characters With Case, 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.