Distinguished Object Entry: NIL

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Distinguished Object Entry: NIL

Name

nil

Class

Distinguished object

Related Types

  • LIST
  • generalized boolean false

Description

nil is a distinguished object in AutoLISP.

In documented AutoLISP behavior:

  • nil denotes falsity in conditional and predicate contexts,
  • nil is also the empty list,
  • (type nil) returns nil, not a distinct runtime type designator such as NIL,
  • listp returns T for nil,
  • null and not return T for expressions that evaluate to nil.

Accordingly, this specification does not treat nil as a separate runtime type in the same sense as INT, REAL, STR, LIST, or SYM.

Representation

It is printed as nil in value position and corresponds semantically to the empty list ().

Valid Operations

  • listp returns T
  • vl-symbolp returns nil
  • type returns nil
  • conditional contexts treat it as false

Compatibility

This is a core language distinction and must not be collapsed to generic Common Lisp symbol or type behavior.

In particular, the Common Lisp type named nil is not an appropriate model for AutoLISP's documented type behavior.