Function Entry: LISTP

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Function Entry: LISTP

Name

listp

Class

Function

Syntax

(listp item)

Arguments and Values

  • item: any AutoLISP value

Description

Determines whether item is a list.

Return Values

Returns T if item is a list; otherwise returns nil.

Autodesk explicitly documents that because nil is both an atom and a list, (listp nil) returns T.

Side Effects

None.

Examples

  • (listp '(a b c)) => T
  • (listp 'a) => nil
  • (listp 4.343) => nil
  • (listp nil) => T

Notes

This entry is one of the clearest vendor statements that nil denotes the empty list in AutoLISP value semantics.

Availability

  • AutoCAD 2026: documented (per Autodesk reference page).
  • BricsCAD V26: presumed compatible (no contradicting page found).
  • Status: AutoCAD documented; BricsCAD presumed-both pending Phase 4 verification.