Normative Rules: NIL and the Empty List

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Normative Rules: NIL and the Empty List

Statement

The symbol nil, the literal (), and the literal '() all denote the same object — the empty list and the false value. (car nil) and (cdr nil) both return nil, not an error.

Vendor Evidence

BricsCAD V26 / macOS direct probe section I:

  • (eq nil '()) = T
  • (car nil) = nil ; (cdr nil) = nil

Cross-references

  • Compare CLHS 26.1.97 — CL also identifies nil with the empty list and accepts (car nil) = nil.
  • Compare R7RS 6.4 — in Scheme nil is a separate symbol; () is the empty list; (car '()) is an error.

Source Notes

Phase-6 BricsCAD V26 / macOS semantics probe section I.