Re: hash undef?


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Re: hash undef?

by moritz (Cardinal)

on Nov 15, 2007 at 12:59 UTC ( [id://650966]=note: print w/replies, xml )

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in reply to hash undef?

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