Re^2: %+ and cloning

[PetaMem]

in reply to Re: %+ and cloning
in thread %+ and cloning

Thanks for your insight.

So I went back to twig technology and copied the hash via

sub copy_hash {
    my $hr = shift // return {}; # get hash to copy or return empty ha
+shref if not given

    my %copy = ();

    while (my ($k, $v) = each %{$hr}) {
        $copy{$k} = $v;
    }

    return \%copy;
}

Which works. So this is it? Best way to go?

[JavaFan]

That depends on ones definition of 'best'. One could also write:

sub copy_hash {
    my $hr = shift // return {};
    my $copy;
    @$copy{keys %$hr} = value %$hr;
    $copy;
}

or just:

sub copy_hash {{%{$_[0]//{}}}}

Or without a sub:

my %copy = %+;

[BrowserUk]

A simple my %copy = %+; is equivalent to your sub. However, that may not be enough!

According to the docs for Tie::Hash::NamedCapture, the values of the tied hash can contain an array reference holding multiple captures due to the re-use of the same named capture. In which case you might need to use something more complex to perform a deep copy operation.

That said, in my simple tests, this doesn't seem to apply to %+. It does apply to %- though.

[JavaFan]

It happens if the tie happens with parameters all => 1, but %+ is tied without them. So even if your tests were less simple, you shouldn't have seen it with %+ (and if you ever do, there's a bug).