CheckDigits::M07_001(3) compute check digits modulo 7 method 1

## SYNOPSIS

use Algorithm::CheckDigits;
\$m001 = CheckDigits('m001');
if (\$m001->is_valid('1234567892')) {
# do something
}
\$cn = \$m001->complete('123456789'); # \$cn = '1234567892'
\$cd = \$m001->checkdigit('1234567892'); # \$cd = '2'
\$bn = \$m001->basenumber('1234567892'); # \$bn = '123456789'

## ALGORITHM

1.
2.
All digits at even positions are added.
3.
The sum of step 1 and 2 is taken modulo 7.
4.
This is the check digit.

## 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 undef if \$number does not consist solely of digits.

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

Return undef otherwise.

checkdigit(\$number)
Returns the check digit belonging to \$number or undef if \$number does not consist solely of digits.

None by default.

## AUTHOR

Mathias Weidner, <[email protected]>