Function Entry: ATOM

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Function Entry: ATOM

Name

atom

Class

Function

Syntax

(atom item)

Arguments and Values

  • item: any value

Description

Returns T if item is not a list; otherwise returns nil.

Return Values

  • T if item is not a list
  • nil otherwise

Side Effects

None.

Affected By

  • the AutoLISP distinction between lists and non-lists

Exceptional Situations

None specific are documented.

Examples

  • (atom 1) => T
  • (atom '(a b)) => nil
  • (atom nil) => T

Compatibility

Autodesk explicitly notes that some other Lisp dialects use different conventions, so this behavior should not be silently replaced by non-AutoLISP semantics.

Notes

Because nil is also the empty list in other AutoLISP contexts, the atom result on nil is particularly important and should be tested against target hosts.

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.