Provided by: libalgorithm-checkdigits-perl_0.50-1_all

#### 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>

```

#### SEEALSO

```       perl, CheckDigits, www.pruefziffernberechnung.de.
```