From: Vassil Nikolov
Subject: Re: how to test for a type specifier?
Date: 
Message-ID: <65292.vnikolov@math.acad.bg>
On Tue, 14 Oct 1997 08:27:00 -0700, 
Kent M Pitman  <······@world.std.com> wrote
in comp.lang.lisp:

... most of the text omitted...

>Sounds like
>a good candidate for next time around, though.  At least
>TYPE-SPECIFIER-P ... 

Yes, I believe it will be nice indeed to include
TYPE-SPECIFIER-P in the language at the next opportunity.

In my opinion, it would be most useful if it tests for
an `actual' type specifier, because this is the version
that users cannot write on their own (or can but at great expense).
In other words, the version where (TYPE-SPECIFER-P FOO) returns
true iff, in the current lexical _and_dynamic_ context,
it is possible to provide a definite answer (be it yes
or no) to a TYPEP/SUBTYPEP question concerning FOO (i.e.,
it is not an error to ask such a question).

The other version, where TYPE-SPECIFIER-P merely tests
for a `potential' type specifier (i.e. if it is a symbol,
or a list built according to the specific syntax rules),
is much easier for the users to implement themselves.

I am *very grateful* to Kent Pitman for his coverage
of the issue.

Best regards,
Vassil.

Vassil Nikolov         <········@bgearn.acad.bg>     (+359-2) 713-3813
Department of Information Research
Institute of Mathematics and Informatics        fax: (+359-2) 9713649
Acad. G. Bonchev, block 8, Sofia 1113, Bulgaria