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.\"
.IX Title "Business::ISSN 3pm"
.TH Business::ISSN 3pm "2018-05-17" "perl v5.26.2" "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($issn)"
The constructor accepts a scalar representing the \s-1ISSN.\s0
.Sp
The string representing the \s-1ISSN\s0 may contain characters
other than [0\-9xX], although these will be removed in the
internal representation.  The resulting string must look
like an \s-1ISSN\s0 \- the first seven characters must be digits and
the eighth character must be a digit, 'x', or 'X'.
.Sp
The string passed as the \s-1ISSN\s0 need not be a valid \s-1ISSN\s0 as
long as it superficially looks like one.  This allows one to
use the \f(CW\*(C`fix_checksum\*(C'\fR method.
.Sp
One should check the validity of the \s-1ISSN\s0 with \f(CW\*(C`is_valid()\*(C'\fR
rather than relying on the return value of the constructor.
.Sp
If all one wants to do is check the validity of an \s-1ISSN,\s0
one can skip the object-oriented  interface and use the
c<\fIis_valid_checksum()\fR> function which is exportable on demand.
.Sp
If the constructor decides it can't create an object, it
returns undef.  It may do this if the string passed as the
\&\s-1ISSN\s0 can't be munged to the internal format.
.ie n .IP "$obj\->checksum" 4
.el .IP "\f(CW$obj\fR\->checksum" 4
.IX Item "$obj->checksum"
Return the \s-1ISSN\s0 checksum.
.ie n .IP "$obj\->as_string" 4
.el .IP "\f(CW$obj\fR\->as_string" 4
.IX Item "$obj->as_string"
Return the \s-1ISSN\s0 as a string.
.Sp
A terminating 'x' is changed to 'X'.
.ie n .IP "$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 \s-1ISSN\s0 does not pass the checksum test.
The constructor accepts invalid \s-1ISSN\s0'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 \s-1ISSN\s0 corresponds to the product one
thinks it does, or that the \s-1ISSN\s0 corresponds to any product
at all.  It only produces a string that passes the checksum
routine.  If the \s-1ISSN\s0 passed to the constructor was invalid,
the error might have been in any of the other nine positions.
.SS "\s-1EXPORTABLE FUNCTIONS\s0"
.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 \s-1ISSN\s0 string and runs it through the checksum
comparison routine.  Returns 1 if the \s-1ISSN\s0 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\-2018, brian d foy <bdfoy@cpan.org>. All rights reserved.
.PP
You may redistribute this under the terms of the Artistic License 2.0.