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Disallowing NIL as a feature
Date: Wed, 7 Aug 85 22:45:47 EDT
From: Kjeld Hvatum <KSH@MIT-MC.ARPA>
FROM: BACHER, STEPHEN E. SENT ON: 07/01/85 AT 08:04 DATE - 07/01/85
Reply to CL flame on disallowing NIL as a feature:
If you make it an error (signalled or otherwise) for NIL to be a
feature, then an awful lot of Macsyma source code will break, for
NIL (the language, that is) is used as a feature name throughout
in #+/#- conditionals.
Since it's been proposed that features be defaultly read in the keyword package
and since :NIL is not what's under discussion, this probably doesn't affect
Macsyma. Presumably you'd have to type #+LISP:NIL to get the problemsome case,
and I don't think anyone does that.
Even if we didn't defaultly read features in the keyword package, I am the one
who originally suggested disallowing NIL as a feature name and I also happen to
maintain the Macsyma sources for Symbolics and I can assure you that if such a
change ever "broke" Macsyma, then it could be easily be fixed in less than 15
minutes using Tags Query Replace.
Let's try to distinguish between the situation of something being affected by
a change and something being broken by a change.