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Postings from June 2004
Stas Bekman <stas@stason.org> writes:
>Why the ideas always come a second after hitting the send button. The obvious
>thing I was missing is to check how pp_defined does the thing. I shouldn't
>have been wasting time searching in the docs :)
>
>Stas Bekman wrote:
>[...]
>> So how do I check in C whether the passed variable (or a random sv) is
>> undef or not if comparing to &PL_sv_undef doesn't work?
>
>So I've changed:
>
>- ST(0) == &PL_sv_undef
>+ (!ST(1) || !SvANY(ST(1))
>
>and voila, it works whether I call:
>
> foo(undef);
>
>or
>
> $x = undef;
> foo($x);
But possibly not for
$x = 42;
...
$x = undef;
foo($x); # SvANY is probably still an SvIV
>
>> am I missing
>> some obvious RTFM section? I've read: 'perlguts:=head2 AVs, HVs and
>> undefined values'
>> but it doesn't seem to be related. There were many other references to
>> undef in the perl manpages, but I didn't find anything useful.
>
>This should probably be added to the perlguts manpage, next to the
>'=head2 AVs, HVs and undefined values' item.
>
>=head How to check arguments for undefine-ness
>...
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