Quick Navigator

 Search Site Miscellaneous Server Agreement Year 2038 Credits

# Manual Reference Pages  -  ALGORITHM::CHECKDIGITS::M16_001 (3)

.ds Aq ’

### NAME

CheckDigits::M16_001 - compute check digits for ISAN

### SYNOPSIS

```

use Algorithm::CheckDigits;

\$isan = CheckDigits(isan);

if (\$isan->is_valid(123A567B8912E01A)) {
# do something
}

\$cn = \$isan->complete(123A567B8912E01);
# \$cn = 123A567B8912E01A

\$cd = \$isan->checkdigit(123A567B8912E01A);
# \$cd = 4

\$bn = \$isan->basenumber(123A567B8912E01A);
# \$bn = 123A567B8912E01

```

### DESCRIPTION

#### ALGORITHM

 1. a(1) = 16 b(i) = a(i) % 17 +d(i), where d(i) is the decimal value of the hexdigit at position i. c(i) = b(i) % 16 a(i) = c(i-1) * 2, for i greater than 1 2. Beginning left for each i = 1..16, a, b, c are computed. 3. The check digit is the value for d(16) where c(16) equals 1. 4. The check digit is appended as hexadecimal value to the number.

#### 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, <mamawe@cpan.org>