Tables returning nil if no value

[Jonathan A Rees <JAR@MC.LCS.MIT.EDU>]

    Date: 27 Mar 86 11:38:39 EST (Thu)
    From: Ashwin Ram <ram at YALE.ARPA>

    I would vote for a predicate TABLE-ENTRY? (like Scott's HT:KEY?) which checks
    whether K has an association in T.

This sort of conflicts with my design which for (set (table-entry foo
bar) '#f) deletes bar's entry in the table; if there's a possibility of
having an entry of #f being different from no entry, then you have to
have a separate deletion primitive.  Things get out of hand quickly --
once you have one feature you want a zillion others.  I say nip them in
the bud.

Jonathan.