NAME

Business::ISSN - Perl extension for International Standard Serial Numbers

SYNOPSIS

  use Business::ISSN;
  $issn_object = new Business::ISSN('1456-5935');
  $issn_object = new Business::ISSN('14565935');
  
  # print the ISSN with hyphens
  print $issn_object->as_string;

  # check to see if the ISSN is valid
  $issn_object->is_valid;
 
  #fix the ISSN checksum.  BEWARE:  the error might not be
  #in the checksum!
  $issn_object->fix_checksum;

  #EXPORTABLE FUNCTIONS
        
  use Business::ISSN qw( is_valid_checksum );
        
  #verify the checksum
  if( is_valid_checksum('01234567') ) { ... }

DESCRIPTION

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->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.

EXPORTABLE FUNCTIONS

Some functions can be used without the object interface. These do not use object technology behind the scenes.

is_valid_checksum('01234567')

Takes the ISSN string and runs it through the checksum comparison routine. Returns 1 if the ISSN is valid, 0 otherwise.

AUTHOR

Sami Poikonen <sp@iki.fi>

Copyright 1999, Sami Poikonen.

This module is released under the terms of the Perl Artistic License.

This module is a derived work from brian d foy's Business::ISBN.

SEE ALSO

Business::ISBN and its documentation.

cpanm Business::ISSN

perl -MCPAN -e shell
install Business::ISSN