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'undef'ing a hash element

by Deda (Novice)
on Aug 26, 2003 at 12:09 UTC ( [id://286666]=perlquestion: print w/replies, xml ) Need Help??

Deda has asked for the wisdom of the Perl Monks concerning the following question:

hi, i have a hash like 
%hash=(
   a => 1
   b => 2
}

[download]
How do I 'undef' a hash entry - not the value, but the key? if i write 
undef $hash{a}

[download]
i get 
%hash=(
   a => undef
   b => 2
}

[download]
What i want to get is 
%hash=(
   b => 2
}

[download]
I need this for %ENV modification (UX: unset equivalent).

Replies are listed 'Best First'.
Re: 'undef'ing a hash element
by antirice (Priest) on Aug 26, 2003 at 12:13 UTC

    I believe delete is what you're looking for.

    Hope this helps.

    antirice    
    The first rule of Perl club is - use Perl
    The     ith rule of Perl club is - follow rule i - 1 for i > 1

[reply]
      This is exactly what I was looking for. thx
[reply]
Re: 'undef'ing a hash element
by arthas (Hermit) on Aug 26, 2003 at 12:17 UTC

    Hi!

    You should use:

    delete $hash{$a}

    [download]

    This removes the key/value pair. undef only sets the key's value to the undefined value.

    Michele.

[reply]
[d/l]
[select]
      This is a little off-topic, but you may find the info useful in the long run. For fun, check out Hash::NoVivify to learn about a related subtlety of hash key management and a module for dealing with it.
[reply]

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