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Postings from August 2009
From: Ed Avis <eda@waniasset.com>
> My question is, does there exist a 'safe hash invert' function in some CPAN
> module? I was imagining something like
>
> my %hash = (a => 1, b => 2);
> my %reverse = safe_hash_invert %hash; # works fine
>
> $hash{c} = 1;
> %reverse = safe_hash_invert %hash; # throws an error 'duplicate values...'
>
> I see Hash::Util and Hash::MoreUtils on CPAN but neither provides such a
> function. Before I write one myself I wanted to check if there is already
> a standard implementation.
I don't think there is and I don't think there's a need.
my %hash = (a => 1, b => 2,
c => 1,
);
my %reverse = reverse %hash;
die "Bummer, the values were not unique!"
if keys(%hash) != keys(%reverse);
Complex, was it? :-)
As the test whether the values are unique would have to build a hash
of the values, there's no point in testing first and then building
the reverted hash.
Jenda
===== Jenda@Krynicky.cz === http://Jenda.Krynicky.cz =====
When it comes to wine, women and song, wizards are allowed
to get drunk and croon as much as they like.
-- Terry Pratchett in Sourcery
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