6.16.2 Type of empty lists

Core Type: <null>

Parent Type: <list>

Type of the null object.

The type <null> is special in that it is considered sub–type of both the type <list> and the types defined with the annotations (list-of ?type). Notice that types defined with the annotations (list ?type0 ?type ...) are not super–types of <null>, because, by definition, they contain at list one item.

Constructor on <null>: <null> type-constructor

Return the null object.

Type predicate on <null>: <null> type-predicate obj

The type predicate is null?. Return #t if obj is the null object; otherwise return #f.