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To: Melvin Smith <mrjoltc...@mindspring.com>
Cc: Perl6 Internals <perl6-intern...@perl.org>
Subject: Re: [RfC] Testing for null
References: <5.1.1.6.2.20031203095021.06224eb0@pop.mindspring.com>
Date: 03 Dec 2003 16:41:32 +0100
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From: boemm...@physik.uni-kl.de (Juergen Boemmels)

Melvin Smith <mrjoltc...@mindspring.com> writes:

[...]

> My intention for PMCNULL was to catch invalid interpreter state, or
> invalid bytecode; cases which used to give us core dumps.
> 
> Explicitly returning PMCNULL and allowing tests on PMCNULL may
> or may not fit into this, depending on your point of view. I'm not even
> certain what my view of it is. Allowing ANY valid test on PMCNULL
> seems to muddy the water by allowing it to actually be used.

There is currently a way of creating such an object:
   null P0
But you can't do anything with this object. If there are valid reasons
to create such an object, there should be a way to test for it.

> The question is: should we allow a NULL register test
> and would this replace Undef as the de facto way to return
> "nothing". Probably the answer is "yes" but I'd like to hear Dan's
> take on it.

There is currently no general Undef, only a PerlUndef, which warns if
used and morphs to a PerlInt when incremented. It might be best to
create a undef.pmc.

bye
boe
-- 
Juergen Boemmels			boemm...@physik.uni-kl.de
Fachbereich Physik			Tel: ++49-(0)631-205-2817
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