[plug] Perl: Intersection of two arrays?

[Simon Newton]

> Here's the routine I ended up going with:
> 
> sub SetIntersection($$)
> {
>    my ($set1,$set2) = @_;
>    my %count = ();
>    my $element;
>    foreach $element (@{$set1}) { $count{$element} |= 1; };
>    foreach $element (@{$set2}) { $count{$element} |= 2; };
>    return grep { $count{$_} == 3 } keys %count;
> }

you could shorten it a bit:

sub SetIntersection
{
   my %count = ();
   foreach (@{$_[0]}) { $count{$_} |= 1; };
   foreach (@{$_[1]}) { $count{$_} |= 2; };
   return grep { $count{$_} == 3 } keys %count;
}

at the expense of becomming unreadable :)

> I still wonder if a custom function written in C could do things a chunk 
> faster. ^_^

If you really wanted speed, you wouldn't be using Perl.

You might want to take a look at Inline::C . I've never used it but I'd
say its what your after. 

Simon N