historical question about CASE

[sandra%orion@cs.utah.edu (Sandra J Loosemore)]

While porting some code between CL implementations, I got bit by the fine
print in the manual about how NIL was not allowed as a singleton key in
CASE, as it could be confused with an empty key list.  It's easy enough
to wrap a pair of parentheses around the NIL, but I got to thinking that
an empty key list is not very interesting anyway.  Does anyone remember why
it was decided to treat NIL as a list instead of a symbol in this context?

Just curious,

-Sandra
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