Multidimensional Arrays - This simple program doesn't work - Tie::File

[SparceMatrix]

Multidimensional Arrays - This simple program doesn't work - Tie::File.

I am trying to create a multidimensional array and I can't seem to access the members of the array. I am using Tie::File to write the contents of a file into an array so that each line is a member of the array. But also, I want break down each record, splitting it so that the record becomes an array as well. I want to wind up with a two dimensional array with the first dimension being the row and the second being split members of the row.

Here is my "TieTest.txt" text file to read from:

One One, One Two, One Three, One Four
Two One, Two Two, Two Three, Two Four
Three One, Three Two, Three Three, Three Four
Four One, Four Two, Four Three, Four Four

And here is the simple program:

#!/usr/bin/perl

use Tie::File;
use Fcntl;

$filename = "TieTest.txt";

tie(@opendata, Tie::File, $filename, mode => O_RDONLY)
  or die "!!!!\n";

@data=@opendata;

print "\n";

foreach $data (@data) {
	print "\$data = $data --> ";
	@split = split ",", $data ;
	$data = @split;
	print "New \$data = $data \n";
	}

print "\n Outside foreach \$data = \"$data\"\n\n";

for($i=0; $i<=$#data; $i++)
{
	print " For row $i --> ";
  for($j=0; $j<4; $j++)
  {
    print "$j: \"$data[$i][$j]\" ";
  }
  print "\n";
}

Does anyone have any idea what I am missing? Should I be applying a different strategy?

 

[PaulTEG]

I'd avoid using reserved words for variable names, and you're using $data, and @data, this could be very confusing.

Also try using use strict; at the top of your script

your die statement should include "$!" as that will give more information on the error

$data and @data, that's asking for trouble methinks

more information on Arrays of Arrays here

Paul
------------------------------------
Spend an hour a week on CPAN, helps cure all known programming ailments ;-)

 

[SparceMatrix]

I made some changes, especially adding "use strict" and made the usual accomodations elsewhere:

#!/usr/bin/perl

use strict;

use Tie::File;
use Fcntl;

my $filename = "TieTest.txt";

tie(my @opendata, 'Tie::File', $filename, mode => O_RDONLY)
  or die "!!!!\n";

my @mydata=@opendata;

print "\n";

foreach my $mydata (@mydata) {
	print "\$mydata = $mydata --> ";
	my @split = split ",", $mydata ;
	$mydata = @split;
	print "New \$mydata = $mydata \n";
	}

# print "\n Outside foreach \$mydata = \"$mydata\"\n\n";

for(my $i=0; $i<=4; $i++)
{
	print " For row $i --> ";
  for(my $j=0; $j<4; $j++)
  {
    print $j . ": \"" . $mydata[$i][$j]. "\" ";
  }
  print "\n";
}

Now, I get the following error just after my first print statement in the nested "for(...) expression:

Can't use string ("4") as an ARRAY ref while "strict refs" in use at MyCode.pl line 31, <$fh> line 8

What does that mean and why am I getting the error? Is there a scope issue for the foreach loop?

Very basically I need to know if it is possible to apply a foreach loop to an array to add a dimension to it and some data to go there at the same time. What could be more natural? I can only assume it's possible, but how?

 

[rharsh]

For this application, you probably want a hash of arrays. To preserve the order of the row names, you'll need to have an array for tracking purposes. Try something like this:

use Tie::File;
tie my @lines, 'Tie::File', 'TieTest.txt' or die;

my (@order, %HofA);

foreach my $line (@lines) {
	for (split /\s*,\s*/, $line) {
		my ($key, $value) = split;
		push @order, $key unless defined $HofA{$key};
		push @{$HofA{$key}}, $value;
	}
}

foreach my $row (@order) {
	print "$row:\n";
	foreach my $col (@{$HofA{$row}}) {
		print "\t$col\n";
	}
}

 

[SparceMatrix]

See this thread for some more solutions and explanations:

http://www.tek-tips.com/viewthread.cfm?page=1&qid=1275479