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Re: Car and Cdr of nil is nil
The use of (CAR NIL) = NIL predates 1971, which is the earliest BBN-Lisp
manual I have.
The operation of CAR and CDR on NIL is somewhat independent of the use
of NIL as a symbol, the empty list, and false. ("this feature really
messes up the type hierarchy"), in that, even if one left CAR and CDR
undefined or "is an error" on NIL, one might still use NIL = () = (NOT
As for "nasty problems for Lisp implementors on stock hardware", this
was a nasty problem 10 years ago, but the technology for handling it,
even on stock hardware, is well in hand. The nastiness for stock
hardware is keeping (setf (car 3215) t) from crashing your system.