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Function CHAR-UPCASE, CHAR-DOWNCASE

Syntax

  • char-upcase charactercorresponding-character
  • char-downcase charactercorresponding-character

Arguments and Values

  • character, corresponding-character - a character.

Description

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.

Examples

(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

Affected By

None.

Exceptional Situations

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

See Also

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

Notes

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}