#!/usr/bin/perl -w
use strict;

my $first = $ARGV[0];
my $second = $ARGV[1];
unless (defined($ARGV[0])) {
	print "Insert filename of the first matrix: ";
	chomp($first = <STDIN>);
}
unless (defined($ARGV[1])) {
	print "Insert filename of the second matrix: ";
	chomp($second = <STDIN>);
}

my @AoA;
my $cols = 0;
my $rows = 0;
my @mat1 = readmatrix ($first);
my ($r1, $c1) = ($rows, $cols);
$cols = 0;
$rows = 0;
my @mat2 = readmatrix ($second);
my ($r2, $c2) = ($rows, $cols);

my @product = multiply(\@mat1, \@mat2);

printmatrix (@product);

sub readmatrix {
	my ($file) = @_;
	open(IN, "$file") || die "can't open file: $!\n";
	while (defined (my $line = <IN>)) {
		my @tmp = split(' ', $line);
		$cols = scalar @tmp;
		$rows++;
		push (@AoA, [@tmp]);
	}
	close IN;
}

sub multiply {
	my ($mat1,$mat2) = @_;
	die "unmatching matrices!\n" unless ($c1 eq $r2);
	my $product;
### HERE IS THE BUG SOMEWHERE... ###
	for (my $i=0; $i<$r1; $i++) {
		for (my $j=0; $j<$c2; $j++) {
            		for (my $k=0; $k<$c1; $k++) {
				$product->[$i][$j] += $mat1->[$i][$k] * $mat2->[$k][$j];
			}
		}
	}
	return $product;
}

sub printmatrix {
	my (@AoA) = @_;
	for (my $x = 0; $x <= $#AoA; $x++) {
		print join("\t", @{$AoA[$x]}), "\n";
	}
}