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# Manual Reference Pages  -  ALGORITHM::CHECKDIGITS::M07_001 (3)

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### NAME

CheckDigits::M07_001 - 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

```

### DESCRIPTION

#### ALGORITHM

 1. All digits are added. 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, <mamawe@cpan.org>