 CheckDigits::MBase_001(3) compute check digits for UPC (US)

## SYNOPSIS

use Algorithm::CheckDigits;
\$rv = CheckDigits('upc');
if (\$rv->is_valid('012345678905')) {
# do something
}
\$cn = \$rv->complete('01234567890');
# \$cn = '012345678905'
\$cd = \$rv->checkdigit('012345678905');
# \$cd = '5'
\$bn = \$rv->basenumber('012345678905');
# \$bn = '01234567890'

## ALGORITHM

1.
Add all digits in odd-numbered positions.
2.
Multiply the sum from step 1 with 3.
3.
Add all digits in even-numbered positions.
4.
Add the product from step 2 and the sum from step 3.
5.
If the sum from step 4 is 0 modulo 10, the check digit is 0. Else the check digit is 10 minus the sum from step 4 taken modulo 10.

## METHODS

is_valid(\$number)
Returns true only if \$number consists solely of numbers and the last digit is a valid check digit according to the algorithm given above.

Returns false otherwise,

complete(\$number)
The check digit for \$number is computed and concatenated to the end of \$number.

Returns the complete number with check digit or '' if \$number does not consist solely of digits and spaces.

basenumber(\$number)
Returns the basenumber of \$number if \$number has a valid check digit.

Return '' otherwise.

checkdigit(\$number)
Returns the checkdigit of \$number if \$number has a valid check digit.

Return '' otherwise.

None by default.

## AUTHOR

Mathias Weidner, <[email protected]>

## THANKS

Aaron W. West pointed me to a fault in the computing of the check digit.