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To: Perl6 Internals <perl6-intern...@perl.org>
Subject: [RfC] Testing for null
Date: 03 Dec 2003 15:46:11 +0100
Message-ID: <m2y8tu0xjg.fsf@helium.physik.uni-kl.de>
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From: boemm...@physik.uni-kl.de (Juergen Boemmels)

Hi,

I'm curently playing around with open calls returning a PMCNULL
instead of a half valid IO-Object. But the main problem with that is
that there is currently no way for the byte-code to detect such a
case.
The if and unless ops call the get_boolean vtable method which throws
an internal exception.
As we can create a PMCNULL with the null_p op there should at least
be a way to test for a PMCNULL. Two possible solutions come to my mind

* A PMCNULL has false semantics. This may be done by letting
  get_boolean return FALSE, or by adding a test to if_p_ic op:
  if(!PMC_IS_NULL($1) && $1->vtable->get_boolean($1))
* Have a special op for this if_null and unless_null which exlusively
  test for NULL.

Comments
boe
-- 
Juergen Boemmels			boemm...@physik.uni-kl.de
Fachbereich Physik			Tel: ++49-(0)631-205-2817
Universitaet Kaiserslautern		Fax: ++49-(0)631-205-3906
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