[grand-rapids-pm-list] Second grade math is giving me problems

[grand-rapids-pm-list at pm.org]

Hi all,

I'm working with bit of code that is so basic and so simple that  
perhaps I can't see the easy explanation as to why I am not getting  
the expected output. I'm really baffled here.

It simply adds or subtracts numbers from a account balance based on  
whether it is a deposit or withdraw. Simple enough, right? Well, i  
guess not for me...

Here is the code:

my @summary = ();

$summary[0] = [ 1, 444.01 ];
$summary[1] = [ 2, 366.41 ];
$summary[2] = [ 1, 62.03 ];
$summary[3] = [ 2, 77.60 ];
$summary[4] = [ 1, 7.23 ];
$summary[5] = [ 2, 66.03 ];
$summary[6] = [ 1, 71.65 ];
$summary[7] = [ 2, 74.88 ];

my $balance = 0;
foreach my $line (@summary) {

         my ($method, $amount) = @{$line};

         print "Cur Balance: $balance ";

         if ($method == 1) {
                 $balance = $balance + $amount;
         } elsif ($method == 2) {
                 $balance = $balance - $amount;
         }

         print "New Balance: $balance\n";

}

As you can likely determine, the @summary variable is an array of  
arrays; the later of which holds two values. The first value being 1  
or 2. 1 for a deposit and 2 for a withdrawal. The second value being  
the amount in question.

With an account balance starting at zero, evaluating these numbers  
should result in an ending balance of zero i.e. the total deposits are  
equal to the total withdrawals. However, while looping over the array,  
I'm getting funny results like long decimal values and a final balance  
of -1.42.

Here is the output i'm seeing:

Cur Balance: 0 New Balance: 444.01
Cur Balance: 444.01 New Balance: 77.6
Cur Balance: 77.6 New Balance: 139.63
Cur Balance: 139.63 New Balance: 62.03
Cur Balance: 62.03 New Balance: 69.26
Cur Balance: 69.26 New Balance: 3.22999999999998
Cur Balance: 3.22999999999998 New Balance: 74.88
Cur Balance: 74.88 New Balance: -1.4210854715202e-14

I suspect running this code through your perl interpreter would give  
you the same results. I'm convinced the problem is something simple,  
but I just don't see it. Anyone have any ideas?

- Brian