Re: OO Perl, iterators

Gregory Toomey <nobody@xxxxxxxxxxx> wrote in comp.lang.perl.misc:
> Anno Siegel wrote:
>
> > Gregory Toomey <nobody@xxxxxxxxxxx> wrote in comp.lang.perl.misc:
> >> I'm a bit confused about the Perl OO syntax. From my reading "foreach"
> >> acts as an iterator.
> >
> > It is a loop construct. An iterator is something that produces
> > values to iterate over, like <> or "each" in Perl.
> >
> >> Any somebody tell me in the standard example below:
> >
> > For all of these, do
> >
> > my @answers = $query->answer;
> >
> >
> >> - how to count the total number of $query->answer
> >
> > my $total = @answers;
> >
> >> - how to access the i'th answer; $query->answer[$i] does not work
> >
> > my $i_th = @answers[ $i];
> >
> >> - how to access a random answer
> >
> > my $rand_ans = @answers[ rand @answers];
> >
> >> thanks
> >> gtoomey
> >> --
> >> use Net::DNS;
> >> my $res = Net::DNS::Resolver->new;
> >> my $query = $res->query("example.com", "NS");
> >>
> >> if ($query) {
> >> foreach $rr (grep { $_->type eq 'NS' } $query->answer) {
> > ^^^
> > You're not running under strict! You've been around long enough to
> > know better.
> >
> >> print $rr->nsdname, "\n";
> >> }
> >> }
> >
> > Anno
>
> That code was from the NET::DNS module.

So? You are responsible for the code you post, even if you take it from
somewhere else.

> I think I found the answer to my original question.
> The syntax $query->answer[$i] is wrong; ($query->answer)[$i] works even
> though it looks strange.

It's a normal list slice, nothing strange about it. However, it
will calculate the entire list of answers each time you want to
extract a single element. Caching the list, as in my code above,
avoids that.

Anno
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