Re: Weird Math revisited

[Bill Stephenson]

I don't know how many people here remember the thread on "weird math" 
but here's the question that I posed awhile back...

I've got a script that takes numbers similar to those below and then 
rounds
them and adds them together using code similar to what is below.

    #!/usr/bin/perl -w
    use strict;
    my $item_1 = "1.655";
    my $item_2 = "1.755";
    my $rnd_1 = (sprintf qq~%.2f~, $item_1);
    my $rnd_2 = (sprintf qq~%.2f~, $item_2);
    print "$rnd_1, $rnd_2";
The code above prints this result (system 10.1.5, perl 5.6.0):
    1.66, 1.75
But shouldn't it be:
    1.66, 1.76
or:
    1.65, 1.75
I'm no math wizard, so if someone could please take the time and tell 
what
I'm missing here I would very much appreciate it!
We all agreed this doesn't work well for finances and I've still not 
found a solution that is recommended for this problem. "Roll your own" 
seems to be the answer most often provided for this question.

With this in mind, I'd like to offer what I'm using now for review by 
those interested. This solution was given to me by Shawn McKinley. One 
of his goals was to make this portable so we can reuse it. I'll be 
using it on OS X 10.3.  I won't even try to pretend I've deciphered all 
of it, but I'd like to know if anyone here can find anything wrong with 
this?

<code>
#!/usr/bin/perl -w
use strict;
my $item_1 = "1.655";
my $item_2 = "1.755";
print round($item_1),"\n";
print round($item_2);
sub round {
  my $t    = shift || 0;
  $t       = sprintf('%015i',int($t*1000));
  $t       =~ m/^\-?(\d*)(\d\d)(\d)$/;
  my($whole,$fraction,$rounder)=($1,$2,$3);
  $whole += 0;
  $fraction++ if($rounder > 4);
  if($fraction > 99) { $whole++; $fraction='00'; }
  return(($t=~/^\-/?'-':'').$whole.'.'.$fraction)
}
</code>
Also, if anyone has a better method, or even a different one, I'd love 
to see it.

Bill