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Ovid (2709)
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Stuff with the Perl Foundation. A couple of patches in the Perl core. A few CPAN modules. That about sums it up.
Find the bug!
I had to add a new feature to my Array::AsHash module. Basically, you might need to get keys and values at particular array indices (think "a list of pairs"), so I needed to allow this:
my $key = $array->key_at(2);
my @keys = $array->key_at(0, 3, -1);
my $keys = $array->key_at(0, 3, -1); # aref
So I wrote code like this (I did something similar for values):
sub key_at {
my $self = CORE::shift;
my $ident = ident $self;
my @keys;
foreach my $index (@_) {
$index *= 2;
CORE::push @keys => $array_for{$ident}[$index];
}
return wantarray ? @keys
: 1 == @_ ? $keys[0]
: \@keys;
}
See the bug? There are a couple of subtle issues here, but one of them is a real whopper. When you see it, you'll know.
FYI: The CORE:: stuff is there because I have methods named shift and push. ident is from Class::Std.
I pour myself a cup of strong coffee. :-)
-- Jarkko Hietaniemi
Hmmm... (Score:2)
--rjray
Re:Hmmm... (Score:2)
Trust me. Once you see the bug, it's a forehead slapper -- if you've encountered this behavior before. It's something that folks often miss because it occurs so rarely, but it's a natural consequence of how Perl behaves.
D'oh! (Score:2)
--rjray
Re:D'oh! (Score:2)
Yeah, I know. It bit me, too :)
Yeah (Score:1)
Lbh'er zbqvslvat gur inyhrf bs gur cnenzrgre yvfg juvpu ner nyvnfrq gb gur inyhrf bs gur inevnoyrf va gur pnyyre'f fpbcr, gurersber zbqvslvat gur pnyyre'f fpbcr, be va guvf pnfr, "ernq-bayl inyhrf".
Of course, your tests should have found this instantly, if you used something like the examples you have there, as it throws up an immediate error.
Why does Perl do this? It's bitten me in the ass a few times, and I can't seriously imagine using it deliberately in code to be maintained.
Re:Yeah (Score:2)
Right in one! Fortunately, the fix is trivial, but it's strange to see if folks don't know what's going on, so I document it.
Re:Yeah (Score:1)
I believe Larry also considers this to be a mistaken feature: in Perl 6
sbenyvnfrf ner ernq-bayl ol qrsnhyg, which would've avoided this bug.(The bit in italics is a spoiler for the original question, so I've put it in Welsh ... erm, I mean rot-13.)
Smylers