What is the most elegant way in Perl to expand an iterator into a list?

Question

I have an iterator with this interface: $hit->next_hsp

The current implementation to listify it is:

my @list;
while ( my $hsp = $hit->next_hsp ) {
    push( @list, $hsp );
}

Now I'm thinking that there might be better ways to do this in less code. What do you say, stackers?

Answer 1

All iterators I've ever seen return undef to signify that they are exhausted. Therefore you should write while (defined(my $hsp = $hit->next_hsp)). The following example demonstrates the fault in the question which tests for truth (aborts at 1) instead of definedness (passes 'liftoff').

use 5.010;
my $hit = __PACKAGE__;

sub next_hsp {
    state $i;
    $i++;
    return ['mumble', 4, 3, 2, 1, 0, 'liftoff']->[$i];
}

# insert snippet from question here

Answer 2

It entirely depends on the iterator implementation. If next_hsp is the only available method, then you're doing it right.