6.4.1 Pair and null class

Builtin Class: <list>

An abstract class respresents lists. A parent class of <null> and <pair>. Inherits <sequence>.

Note that a cirular list is also an instance of the <list> class, while R5RS procedure list? returns false on the circular lists and dotted lists.

(use srfi-1) (list? (circular-list 1 2)) => #f (is-a? (circular-list 1 2) <list>) => #t

Builtin Class: <null>

A class of empty list. () is the only instance.

Builtin Class: <pair>

A class of pairs.