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.IX Title "Sort::Key::Register 3"
.TH Sort::Key::Register 3 2025-07-14 "perl v5.42.0" "User Contributed Perl Documentation"
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.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\*(Aqt 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 USAGE
.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 \*(Aquse\*(Aq 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.