#!/user/bin/perl
use strict;
use warnings;
use Data::Dumper;
use feature 'say';

sub matrix_write_file {
    my ($filename, $matrix) = @_;

    open(my $wfh, '>', $filename)
	or die "Could not open file '$filename' $!";

    # print the whole thing with refs
    for my $aref ( @$matrix ) {
	say $wfh "@$aref";
    }

    close $wfh
	or die "Could not close file '$filename' $!";

    return;
}

sub matrix_read_file {
    my $matrix_name;
    my ($filename) = @_;

    open (my $rfh, $filename)
	or die "Could not open $filename: $!";

    while (my $line = <$rfh>) {
        chomp($line);
        next if $line =~ /^\s*$/; # skip blank lines
        if ($line =~ /^([A-Za-z]\w*)/) {
            $matrix_name = $1;
        } else {
	    my (@row)
		= split (/\s+/, $line);

	    push (@{$matrix_name}, \@row);
		# insert the row-array into
		# the outer matrix array
        }
    }
    close $rfh
	or die "Could not close file '$filename' $!";

    return $matrix_name;
}

my @matrix = ( [1, 2, 3],
	       [4, 5, 6],
	       [7, 8, 9]
    );

my $filename = 'matrix.txt';

matrix_write_file($filename, \@matrix);

print Dumper matrix_read_file($filename);

__END__

$ perl test.pl
$VAR1 = [
          [
            '1',
            '2',
            '3'
          ],
          [
            '4',
            '5',
            '6'
          ],
          [
            '7',
            '8',
            '9'
          ]
        ];

$ cat matrix.txt
1 2 3
4 5 6
7 8 9

##</code><code>##

# print the whole thing with refs faster than for
# but you are destroying the AoA (matrix)
while ( defined ( my $aref = shift @$matrix ) ) {
    say $wfh "@$aref";
}

##</code><code>##

#!/user/bin/perl
use strict;
use warnings;
use Data::Dumper;
use feature 'say';
use IO::All -utf8;
# use Benchmark qw(:all) ; # WindowsOS
use Benchmark::Forking qw( timethese cmpthese ); # UnixOS

sub matrix_write_file {
    my ($filename, $matrix) = @_;
    open(my $wfh, '>', $filename)
	or die "Could not open file '$filename' $!";

    # print the whole thing with refs
    for my $aref ( @$matrix ) {
	say $wfh "@$aref";
    }

    close $wfh
	or die "Could not close file '$filename' $!";

    return;
}

sub matrix_read_file {
    my $matrix_name;
    my ($filename) = @_;

    open (my $rfh, $filename)
	or die "Could not open $filename: $!";

    while (my $line = <$rfh>) {
        chomp($line);
	my (@row)
	    = split (/\s+/, $line);

	push (@{$matrix_name}, \@row);
    }

    close $rfh
	or die "Could not close file '$filename' $!";

    return $matrix_name;
}

sub writeMatrix2File{
    my ( $filename , $matrix ) = @_;
    my $iol = io($filename)->lock;
    while (defined(my $line = shift @$matrix)) {
	# io($filename)->appendln(join ' ', map "$_", @$line);
	$iol->println(join ' ', map "$_", @$line)
    }
    $iol->unlock;
}

sub readMatrixFromFile{
    my $matrix;
    my ( $filename ) = @_;
    my @lines = io($filename)->chomp->slurp;
    while (defined (my $line = shift @lines)){
	my (@row)
	    = split (/\s+/, $line);
	push (@{$matrix}, \@row);
    }
    return $matrix;
}

sub manual {
    my $matrix = [ [1, 2, 3],
		   [4, 5, 6],
		   [7, 8, 9] ];

    my $filename = 'matrix.txt';

    matrix_write_file($filename, $matrix);
    matrix_read_file($filename);
}

sub module {
    my $matrix = [ [1, 2, 3],
		   [4, 5, 6],
		   [7, 8, 9] ];

    my $filename = 'matrix.txt';

    writeMatrix2File($filename, $matrix);
    readMatrixFromFile($filename);
}

manual();
module();

my $results = timethese(1000000, { Manual => \&manual,
				   Module => \&module, }, 'none');
cmpthese( $results );

__END__

:~/PerlMonks$ perl matrix.pl
          Rate Module Manual
Module  1895/s     --   -84%
Manual 12054/s   536%     --

##</code><code>##

#!/user/bin/perl
use strict;
use warnings;
use Data::Dumper;
use IO::All -utf8;

sub writeMatrix2File{
    my ( $filename , $matrix ) = @_;
    my $iol = io($filename)->lock;
    while (defined(my $line = shift @$matrix)) {
	# io($filename)->appendln(join ' ', map "$_", @$line);
	$iol->println(join ' ', map "$_", @$line)
    }
    $iol->unlock;
}

sub readMatrixFromFile{
    my $matrix;
    my ( $filename ) = @_;
    my @lines = io($filename)->chomp->slurp;
    while (defined (my $line = shift @lines)){
	my (@row)
	    = split (/\s+/, $line);
	push (@{$matrix}, \@row);
    }
    return $matrix;
}

my $matrix = [ [1, 2, 3],
	       [4, 5, 6],
	       [7, 8, 9] ];

my $filename = 'matrix.txt';

writeMatrix2File($filename, $matrix);
print Dumper readMatrixFromFile($filename);

__END__

~/PerlMonks$ perl matrix.pl
$VAR1 = [
          [
            '1',
            '2',
            '3'
          ],
          [
            '4',
            '5',
            '6'
          ],
          [
            '7',
            '8',
            '9'
          ]