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.\"
.IX Title "Sort::Key::Register 3pm"
.TH Sort::Key::Register 3pm "2020-11-09" "perl v5.32.0" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
Sort::Key::Register \- tell Sort::Key how to sort new data types.
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 3
\&  use Sort::Key::Register Person =>
\&      sub { $_\->surname, $_\->name },
\&      qw(string string);
\&
\&  use Sort::Key::Register \*(AqColor::Component\*(Aq => \*(Aqinteger\*(Aq;
\&
\&  use Sort::Key::Register Color =>
\&      sub { $_\->R, $_\->G, $_\->B },
\&      (\*(AqColor::Component\*(Aq) x 3;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Sort::Key::Register allows one to register new data types with
Sort::Key so that they can be sorted as natively supported ones.
.PP
It works as a pragma module and doesn't export any function, all its
functionality is provided via \f(CW\*(C`use\*(C'\fR:
.PP
.Vb 1
\&  use Sort::Key::Register ...
.Ve
.PP
To avoid collisions between modules registering types with the same
name, you should qualify them with the package name.
.PP
.Vb 1
\&  use Sort::Key::Register \*(AqMyPkg::foo\*(Aq => sub { $_ }, \*(Aq\-int\*(Aq;
\&
\&  # or using _\|_PACKAGE_\|_:
\&  use Sort::Key::Register _\|_PACKAGE_\|_, sub { $_ }, \*(Aq\-int\*(Aq;
.Ve
.SS "\s-1USAGE\s0"
.IX Subsection "USAGE"
.ie n .IP "use Sort::Key::Register $name => \e&multikeygen, @keytypes;" 4
.el .IP "use Sort::Key::Register \f(CW$name\fR => \e&multikeygen, \f(CW@keytypes\fR;" 4
.IX Item "use Sort::Key::Register $name => &multikeygen, @keytypes;"
registers type \f(CW$name\fR.
.Sp
\&\f(CW&multikeygen\fR is the multi-key extraction function for the type and
\&\f(CW@keytypes\fR are the types of the extracted keys.
.ie n .IP "use Sort::Key::Register $name => $keytype;" 4
.el .IP "use Sort::Key::Register \f(CW$name\fR => \f(CW$keytype\fR;" 4
.IX Item "use Sort::Key::Register $name => $keytype;"
this 'use' is useful for simple types that are sorted as another type
already registered, maybe changing the direction of the sort
(ascending or descending).
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Sort::Key, Sort::Key::Maker.
.SH "AUTHOR"
.IX Header "AUTHOR"
Salvador Fandiño, <sfandino@yahoo.com>
.SH "COPYRIGHT AND LICENSE"
.IX Header "COPYRIGHT AND LICENSE"
Copyright (C) 2005, 2014 by Salvador Fandiño
.PP
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself, either Perl version 5.8.4 or,
at your option, any later version of Perl 5 you may have available.