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.

EXPORT

None by default.

AUTHOR

Mathias Weidner, <mathias@weidner.in-bad-schmiedeberg.de>

SEE ALSO

perl, CheckDigits, www.pruefziffernberechnung.de.