NAME
List::Categorize - Categorize list items into a tree of named sublists
VERSION
This documentation describes List::Categorize version 0.04.
SYNOPSIS
use List::Categorize qw(categorize);
my %odds_and_evens = categorize { $_ % 2 ? 'ODD' : 'EVEN' } (1..9);
# %odds_and_evens now contains
# ( ODD => [ 1, 3, 5, 7, 9 ], EVEN => [ 2, 4, 6, 8 ] )
my %capitalized = categorize {
# Transform the element before placing it in the tree.
$_ = ucfirst $_;
# Use the first letter of the element as the first-level category,
# then the first 2 letters as a second-level category
substr($_, 0, 1), substr($_, 0, 2);
} qw( apple banana antelope bear canteloupe coyote ananas );
# %capitalized now contains
# (
# A => { An => ['Antelope', 'Ananas'], Ap => ['Apple'], },
# B => { Ba => ['Banana'], Be => ['Bear'], },
# C => { Ca => ['Canteloupe'], Co => ['Coyote'] },
# )DESCRIPTION
A simple module that creates a tree by applying a specified rule to each element of a provided list.
EXPORT
Nothing by default.
SUBROUTINES
categorize BLOCK LIST
my %tree = categorize { $_ > 10 ? 'Big' : 'Little' } @list;categorize creates a tree by running BLOCK for each element in LIST. The block should return a list of "categories" for the current element, i.e a list of scalar values corresponding to the sequence of subtrees under which this element will be placed. If the block returns an empty list, or a list containing an undef, the corresponding element is not placed in the resulting tree.
The resulting tree contains a key for each top-level category. Values are either references to subtrees, or references to arrayrefs of elements (depending on the depth of the categorization).
Within the block, $_ refers to the current list element. Elements can be modified before they're placed in the target tree by modifying the $_ variable:
my %tree = categorize { $_ = uc $_; 'List' } qw( one two three );
# %tree now contains ( List => [ 'ONE', 'TWO', 'THREE' ] )NOTE: The categorizer should return a list of strings, or undef. Other values are reserved for future use, and may cause unpredictable results in the current version. When using multi-level categorization, the categorizer should always return the same number of keys.
SEE ALSO
Previous versions of this module only handled one-level categorization, while multi-level categorization was implemented in List::Categorize::Multi. Now both modules have been merged into List::Categorize, therefore List::Categorize::Multi is deprecated.
AUTHOR
Bill Odom, <wnodom at cpan.org> (original author), Laurent Dami, <dami at cpan.org> (added the multi-level categorization)
BUGS
None known.
Please report any bugs or feature requests to bug-list-categorize at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=List-Categorize.
SUPPORT
You can find documentation for this module with the perldoc command.
perldoc List::CategorizeYou can also look for information at:
- RT: CPAN's request tracker
- AnnoCPAN: Annotated CPAN documentation
- CPAN Ratings
- Search MetaCPAN
- Github repository
COPYRIGHT & LICENSE
Copyright (c) 2009 Bill Odom, 2017 Laurent Dami.
This module is free software; you can redistribute it and/or modify it under the same terms as Perl 5.10.0. For more details, see the full text of the licenses at http://www.perlfoundation.org/artistic_license_2_0, and http://www.gnu.org/licenses/gpl-2.0.html.
This program is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose.