Characters in

About Characters

Characters are objects which represent an item in a quantity of text (e.g. a string or text stream).

Characters are represented as #\ followed by its name (e.g. #\A, #\9, #\!, #\Space).

Comparing

In addition to char=, char< and char>, there are also char<= and char>= as well as case-insensitive versions such as char-equal and char-greaterp.

Ordering

Characters can be converted to and from integers. (But they are not integers - they are a distinct type.) The specification leaves the exact ordering of characters to the implementation. This means one should be careful not to assume (char> #\a #\A) or similar assumptions of ordering of characters. The standard does specify that (char< #\A #\Z) and (char< #\a #\z) and (char< #\0 #\9) must be true.

Types of characters

Common Lisp has several predicates to determine what "type" of character a specific character is such as alphanumericp, digit-char-p and graphic-char-p. There are also upper-case-p and lower-case-p to determine the case of the character.