ANSI Common Lisp 13 Characters 13.1 Character Concepts
13.1.4 Character Categories
There are several (overlapping) categories of characters that have no formally
associated type but that are nevertheless useful to name.
characters with case
(uppercase and lowercase characters),
and digits (in a given radix).
For each implementation-defined attribute of a character,
the documentation for that implementation must specify whether
characters that differ only in that attribute are permitted to differ
in whether are not they are members of one of the aforementioned categories.
Note that these terms are defined independently of any special syntax
which might have been enabled in the current readtable.
18.104.22.168 Graphic Characters
22.214.171.124 Alphabetic Characters
126.96.36.199 Characters With Case
188.8.131.52 Numeric Characters
184.108.40.206 Alphanumeric Characters
220.127.116.11 Digits in a Radix