#!/usr/bin/perl
use strict;
use warnings;
use PDL;
use PDL::NiceSlice;
 
sub kron{
	my $A = shift;
	my $B = shift;
	my ($r0, $c0) = $A->dims;
	my ($r1, $c1) = $B->dims;
	my $kron = zeroes($r0 * $r1, $c0 * $c1);
	for(my $i = 0; $i < $r0; ++$i){
		for(my $j = 0; $j < $c0; ++$j){
			$kron(
				($i * $r1) : (($i + 1) * $r1 - 1),
				($j * $c1) : (($j + 1) * $c1 - 1)
			) .= $A($i,$j) * $B;
		}
	}
	return $kron;
}