Implement 'char-upcase', 'char-downcase', and 'char-titlecase' in Scheme

These should each return the uppercase/lowercase/titlecase/foldcase equivalent of char.
http://www.scheme.com/tspl4/objects.html#./objects:s206

(char-upcase #\g)

Traceback (most recent call last):
File "stdin", line 1, col 2
RunTimeError: unbound variable 'char-upcase'

(char-downcase #\g)

Traceback (most recent call last):
File "stdin", line 1, col 2
RunTimeError: unbound variable 'char-downcase'

 (char-titlecase #\g)

Traceback (most recent call last):
File "stdin", line 1, col 2
RunTimeError: unbound variable 'char-titlecase'

Comments (4)