NAME
    List::Util::groupby - Group items of a list into several (possibly
    multilevel) buckets

VERSION
    This document describes version 0.003 of List::Util::groupby (from Perl
    distribution List-Util-groupby), released on 2023-09-30.

SYNOPSIS
     use List::Util::groupby qw(groupby hgroupby);

     my @buckets = groupby { $_ % 2 } 1..10; # => [ [2,4,6,8,10], [1,3,5,7,9] ]
     my @buckets = groupby { [$_ % 2, $_ % 3] } 1..10; # => [ [ [6], [4,10], [2,8]], [ [3,9], [1,7], [5] ] ]

     my @recs = (
       {name=>"andi",date=>"2023-09-29",result=>9.8},
       {name=>"andi",date=>"2023-09-30",result=>10.3},
       {name=>"budi",date=>"2023-09-29",result=>11.1},
       {name=>"budi",date=>"2023-09-30",result=>10.5},
     my %buckets = hgroupby { $_->{name} } @recs;
     # => (
     #   andi => [ {name=>"andi",date=>"2023-09-29",result=>9.8} , {name=>"andi",date=>"2023-09-30",result=>10.3} ],
     #   budi => [ {name=>"budi",date=>"2023-09-29",result=>11.1}, {name=>"budi",date=>"2023-09-30",result=>10.5} ],
     # )

     my %buckets = hgroupby { [$_%2, $_%3] } 1..10;
     #{
     #  "0" => { "0" => [6], "1" => [4, 10], "2" => [2, 8] },
     #  "1" => { "0" => [3, 9], "1" => [1, 7], "2" => [5] },
     #}

DESCRIPTION
    This module provides "groupby".

FUNCTIONS
    Not exported by default but exportable.

  groupby
    Usage:

     @buckets = groupby CODE ARRAY

    Group a list into several buckets.

    In CODE, $_ (as well as $_[0]) is set to array element. $_[1] is set to
    the index of the element, so you can still group elements by their
    position. Code is expected to return an integer index to indicate which
    bucket the item should be grouped into. Code can also return an arrayref
    of integer indices for multilevel buckets.

    Return a (possibly multilevel) array of arrayrefs.

  hgroupby
    Usage:

     %buckets = hgroupby CODE ARRAY

    Just like "groupby", except code is expected to return keys (of arrayref
    of keys) and the function will return a (possibly multilevel) hash of
    arrayrefs.

HOMEPAGE
    Please visit the project's homepage at
    <https://metacpan.org/release/List-Util-groupby>.

SOURCE
    Source repository is at
    <https://github.com/perlancar/perl-List-Util-groupby>.

SEE ALSO
    Array::Group, Array::GroupBy, List::GroupBy

AUTHOR
    perlancar <perlancar@cpan.org>

CONTRIBUTING
    To contribute, you can send patches by email/via RT, or send pull
    requests on GitHub.

    Most of the time, you don't need to build the distribution yourself. You
    can simply modify the code, then test via:

     % prove -l

    If you want to build the distribution (e.g. to try to install it locally
    on your system), you can install Dist::Zilla,
    Dist::Zilla::PluginBundle::Author::PERLANCAR,
    Pod::Weaver::PluginBundle::Author::PERLANCAR, and sometimes one or two
    other Dist::Zilla- and/or Pod::Weaver plugins. Any additional steps
    required beyond that are considered a bug and can be reported to me.

COPYRIGHT AND LICENSE
    This software is copyright (c) 2023 by perlancar <perlancar@cpan.org>.

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.

BUGS
    Please report any bugs or feature requests on the bugtracker website
    <https://rt.cpan.org/Public/Dist/Display.html?Name=List-Util-groupby>

    When submitting a bug or request, please include a test-file or a patch
    to an existing test-file that illustrates the bug or desired feature.