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Re: hash undef?

by moritz (Cardinal)
on Nov 15, 2007 at 12:59 UTC ( #650966=note: print w/replies, xml ) Need Help??

in reply to hash undef?

if (not defined $time{$recordNumber}){ ... }

You can also check with exists in hashes, the semantic is a little bit different.

Update: A bit explanation: == compares numbers, so in the expression $foo == undef the undef is promoted to 0 and compared with $foo - not what you want.

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Re^2: hash undef?
by Anonymous Monk on Nov 15, 2007 at 15:16 UTC

    perl -wMstrict -e "my %hash = (foo => 'x', bar => '', baz => undef); for (qw/foo bar baz quux/) { printf qq($_ exists:%s: $_ defined:%s: $_ true:%s: \n), exists($hash{$_}), defined($hash{$_}), $hash{$_} ? 1 : '' }" foo exists:1: foo defined:1: foo true:1: bar exists:1: bar defined:1: bar true:: baz exists:1: baz defined:: baz true:: quux exists:: quux defined:: quux true::
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