perl-Business-ISSN

Perl extension for International Standard Serial Numbers

* new($issn) The constructor accepts a scalar representing the ISSN. The string representing the ISSN may contain characters other than [0-9xX], although these will be removed in the internal representation. The resulting string must look like an ISSN - the first seven characters must be digits and the eighth character must be a digit, 'x', or 'X'. The string passed as the ISSN need not be a valid ISSN as long as it superficially looks like one. This allows one to use the 'fix_checksum' method. One should check the validity of the ISSN with 'is_valid()' rather than relying on the return value of the constructor. If all one wants to do is check the validity of an ISSN, one can skip the object-oriented interface and use the c<is_valid_checksum()> function which is exportable on demand. If the constructor decides it can't create an object, it returns undef. It may do this if the string passed as the ISSN can't be munged to the internal format. * $obj->checksum Return the ISSN checksum. * $obj->as_string Return the ISSN as a string. A terminating 'x' is changed to 'X'. * $obj->is_valid Returns 1 if the checksum is valid. Returns 0 if the ISSN does not pass the checksum test. The constructor accepts invalid ISSN's so that they might be fixed with 'fix_checksum'. * $obj->fix_checksum Replace the eighth character with the checksum the corresponds to the previous seven digits. This does not guarantee that the ISSN corresponds to the product one thinks it does, or that the ISSN corresponds to any product at all. It only produces a string that passes the checksum routine. If the ISSN passed to the constructor was invalid, the error might have been in any of the other nine positions.