Andrew Curry schreef:
> be very careful with exists, it auto creates the structure
> use Data::Dumper;
> my %hash;
> if (exists $hash{a}{b}) {}
> print Dumper(\%hash)
> then the next time you use exists it is there.
> defined is much safer as it doesnt do this.
No, the difference here is not between exists() and defined().
To be able to check the definedness (or the existence) of $h{foo}{bar},
$h{foo} is created first (auto-vivification).
Neither exists() nor defined() short-cuts hash-levels.
perl -MData::Dumper -wle'
my %hash;
if ( defined $hash{foo}{bar} ) {};
print Dumper \%hash;
'
$VAR1 = {
'foo' => {}
};
(same with exists())
Solution: test $h{foo} first:
if ( exists( $hash{foo} ) and
exists( $hash{foo}{bar} ) )
{ ... }
--
Affijn, Ruud
"Gewoon is een tijger."
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