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# NAME

CheckDigits::MBase_003 - compute check digits for SICI (Serial Item and Contribution Identifier)

# SYNOPSIS

``````  use Algorithm::CheckDigits;

\$sici = CheckDigits('sici');

if (\$sici->is_valid('0784-8679(20040308)6:<138>2.0.TX;2-H')) {
# do something
}

\$cn = \$sici->complete('0784-8679(20040308)6:<138>2.0.TX;2-');
# \$cn = '0784-8679(20040308)6:<138>2.0.TX;2-H'

\$cd = \$sici->checkdigit('0784-8679(20040308)6:<138>2.0.TX;2-H');
# \$cd = 'H'

\$bn = \$sici->basenumber('0784-8679(20040308)6:<138>2.0.TX;2-H');
# \$bn = '0784-8679(20040308)6:<138>2.0.TX;2-';
``````

# DESCRIPTION

## ALGORITHM

0

In the string describing the number all letters (A-Z) are replaced with numbers 10-35 accordingly. All other non-numbers are replaced by 36.

1

Beginning right the numbers at all odd positions are added.

2

The sum from step 1 is multiplied by 3.

3

Beginning right the numbers at all even positions are added.

4

The sums from step 2 and 3 are added.

5

The sum from step 4 is taken modulo 37.

6

The checksum is 37 minus the sum from step 5 where numbers from 10 to 35 are represented by 'A' to 'Z' accordingly and 36 is represented by '#'.

## METHODS

is_valid(\$number)

Returns true only if the last letter is a valid check letter according to the algorithm given above.

Returns false otherwise,

complete(\$number)

The check letter for `\$number` is computed and appended the end of `\$number`.

Returns the complete number with check letter or ''.

basenumber(\$number)

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

Return '' otherwise.

checkdigit(\$number)

Returns the check letter of `\$number` if `\$number` has valid check digits.

Return '' otherwise.

None by default.

# AUTHOR

Mathias Weidner, `<mamawe@cpan.org>`

# SEE ALSO

perl, CheckDigits, www.pruefziffernberechnung.de, http://sunsite.berkeley.edu/SICI/sici.pdf