My work place won't allow us to install any modules so that option isn't for me. So decided to look at this link http://en.wikipedia.org/wiki/CUSIP and follow the pseudocode there and attempt to code it in Perl.
And i came up with the following:
sub cusip_check_digit
{
my $cusip = shift; ## Input: an 8-character CUSIP
my $v = 0; ## numeric value of the digit c (below)
my $sum = 0;
for (my $i = 0; $i < 8; $i++)
{
my $c = substr ($cusip, $i, 1); ## $c is the ith character of cusip
if ($c =~ /\d/) ## c is a digit then
{
$v = $c; ## numeric value of the digit c
}
elsif ($c =~ /\w/)
{
my $p = ord($c) - 64; ## ordinal position of c in the alphabet (A=1, B=2...)
$v = $p + 9;
}
if (0 != $i % 2) ## check to see if $i is even (we invert due to Perl starting points)
{
$v = $v * 2;
}
$sum = $sum + int ($v / 10) + $v % 10;
}
$v = (10 - ($sum % 10)) % 10;
print "v is: $v\n";
#return (10 - ($sum % 10)) % 10
}
cusip_check_digit('90137F10'); ## should return 3 ** Now works **
cusip_check_digit('68243Q10'); ## should return 6 ** Now works **
Not exactly sure why it isn't working.
I think your problem is this line:
$sum = $sum + $v / 10 + $v % 10;
The wiki says 'div' and 'mod'. Which implies integer division, and that's not what it's doing.
Change it to:
$sum = $sum + int ( $v / 10 ) + $v % 10;
And you get the desired result of '3'. I haven't checked it with any other values though, so you'd probably best check.
Edit: Second problem is because we run from 0 to 7 rather than 1 to 8 like in the example. That means 'is i
even' test gets the wrong digit. Easy enough to solve by inverting the logic (test for 'odd' not 'even').
Change that bit to:
if (0 != $i % 2) {
$v = $v * 2;
}