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.\"
.IX Title "Business::ISSN 3"
.TH Business::ISSN 3 2023-07-25 "perl v5.38.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH NAME
Business::ISSN \- Perl extension for International Standard Serial Numbers
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 2
\&        use Business::ISSN;
\&        $issn_object = Business::ISSN\->new(\*(Aq1456\-5935\*(Aq);
\&
\&        $issn_object = Business::ISSN\->new(\*(Aq14565935\*(Aq);
\&
\&        # print the ISSN (with hyphen)
\&        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!
\&        $issn_object\->fix_checksum;
\&
\&        #EXPORTABLE FUNCTIONS
\&
\&        use Business::ISSN qw( is_valid_checksum );
\&
\&        #verify the checksum
\&        if( is_valid_checksum(\*(Aq01234567\*(Aq) ) { ... }
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
.IP new($issn) 4
.IX Item "new($issn)"
The constructor accepts a scalar representing the ISSN.
.Sp
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'.
.Sp
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 \f(CW\*(C`fix_checksum\*(C'\fR method.
.Sp
One should check the validity of the ISSN with \f(CWis_valid()\fR
rather than relying on the return value of the constructor.
.Sp
If all one wants to do is check the validity of an ISSN,
one can skip the object-oriented  interface and use the
c<\fBis_valid_checksum()\fR> function which is exportable on demand.
.Sp
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.
.ie n .IP $obj\->checksum 4
.el .IP \f(CW$obj\fR\->checksum 4
.IX Item "$obj->checksum"
Return the ISSN checksum.
.ie n .IP $obj\->as_string 4
.el .IP \f(CW$obj\fR\->as_string 4
.IX Item "$obj->as_string"
Return the ISSN as a string.
.Sp
A terminating 'x' is changed to 'X'.
.ie n .IP $obj\->is_valid 4
.el .IP \f(CW$obj\fR\->is_valid 4
.IX Item "$obj->is_valid"
Returns 1 if the checksum is valid.
.Sp
Returns 0 if the ISSN does not pass the checksum test.
The constructor accepts invalid ISSN's so that
they might be fixed with \f(CW\*(C`fix_checksum\*(C'\fR.
.ie n .IP $obj\->fix_checksum 4
.el .IP \f(CW$obj\fR\->fix_checksum 4
.IX Item "$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.
.SS "EXPORTABLE FUNCTIONS"
.IX Subsection "EXPORTABLE FUNCTIONS"
Some functions can be used without the object interface.  These
do not use object technology behind the scenes.
.IP is_valid_checksum('01234567') 4
.IX Item "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.
.SH AUTHOR
.IX Header "AUTHOR"
Currently maintained by brian d foy \f(CW\*(C`<brian.d.foy@gmail.com>\*(C'\fR.
.PP
Original module by Sami Poikonen, based on Business::ISBN by brian d foy.
.PP
This module is released under the terms of the Perl Artistic License.
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
Copyright © 1999\-2021, brian d foy <bdfoy@cpan.org>. All rights reserved.
.PP
You may redistribute this under the terms of the Artistic License 2.0.