XML::LibXML::NodeList get

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

I have been making good use of XML::LibXML and often have to make use of the get_node function of XML::LibXML::NodeList

I understand that because of xpath it uses a 1 based array rather than a 0 based array. But if I do make the mistake of deriving the 0th value (I am only human :)), then rather than getting an undef or similar I seem to get the -1th value

I can find no mention of this in cpan. Any ideas why this is?

Comment on XML::LibXML::NodeList get_node

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Re: XML::LibXML::NodeList get_node by tobyink (Canon) on Apr 09, 2014 at 11:21 UTC
`get_node` is implemented much like this: `sub get_node { my ($self, $pos) = @_; $self->[$pos - 1]; }` [download] So `$nodelist->get_node(0)` is the same as `$arrayref->[-1]`. I wouldn't rely on it if I were you though. It's undocumented behaviour that is merely an accident of the internal implementation of XML::LibXML::NodeList, and could theoretically change in the future. `use Moops; class Cow :rw { has name => (default => 'Ermintrude') }; say Cow->new->name`	[reply] [d/l] [select]

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Re: XML::LibXML::NodeList get_node
by tobyink (Canon) on Apr 09, 2014 at 11:21 UTC

get_node is implemented much like this:

sub get_node {
   my ($self, $pos) = @_;
   $self->[$pos - 1];
}
[download]

So $nodelist->get_node(0) is the same as $arrayref->[-1].

I wouldn't rely on it if I were you though. It's undocumented behaviour that is merely an accident of the internal implementation of XML::LibXML::NodeList, and could theoretically change in the future.

use Moops; class Cow :rw { has name => (default => 'Ermintrude') }; say Cow->new->name

[reply]
[d/l]
[select]