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lib/Acme/Math/PerfectChristmasTree.pm  view on Meta::CPAN

package Acme::Math::PerfectChristmasTree;

use warnings;
use strict;
use Exporter;
use Carp;
use Math::Trig qw/pi/;

use vars qw/$VERSION @ISA @EXPORT_OK/;
BEGIN {
    $VERSION = '0.02';
    @ISA     = qw/Exporter/;
    @EXPORT_OK = qw/calc_perfect_christmas_tree/;
}

sub calc_perfect_christmas_tree {
    my $tree_height = shift;

    if ($tree_height <= 0) {
        croak 'Tree height must be a number greater than zero.';
    }

    my $pi = pi();
    return (
        'number_of_baubles' => _round(sqrt(17) / 20 * $tree_height),
        'tinsel_length' => 13 * $pi / 8 * $tree_height,
        'lights_length' => $pi * $tree_height,
        'star_or_fairy_height' => $tree_height / 10,
    );
}

sub _round {
    my $value = shift;

    return int($value + 0.5);
}

1;
__END__

=encoding utf8

=head1 NAME

Acme::Math::PerfectChristmasTree - Calculate the perfect Christmas tree


=head1 VERSION

This document describes Acme::Math::PerfectChristmasTree version 0.02


=head1 SYNOPSIS

    use Acme::Math::PerfectChristmasTree qw/calc_perfect_christmas_tree/;

    my $tree_height  = 140; #<= centimeter
    my %perfect_tree = calc_perfect_christmas_tree($tree_height);

    # Content of %perfect_tree
    #
    # 'star_or_fairy_height' => 14,
    # 'tinsel_length'        => 714.712328691678,
    # 'number_of_baubles'    => 29,
    # 'lights_length'        => 439.822971502571


=head1 DESCRIPTION

This module calculates perfect Christmas tree. Sorry, "perfect Christmas tree" is not a data tree.
So it has nothing to do with data structure.

This module is using an equation which was devised by mathematics club of The University Of Sheffield.
For more details, refer to the following web site.

L<http://www.shef.ac.uk/news/nr/debenhams-christmas-tree-formula-1.227810>


=head1 METHODS

=over

=item calc_perfect_christmas_tree

Calculates perfect Christmas tree.

This function needs an argument which specify height of tree (please input as centimeter).

This function returns a hash. Keys of hash are...

    'star_or_fairy_height'
    'tinsel_length'
    'number_of_baubles'
    'lights_length'

(Values of hash related to length or height are expressed as centimeter).

=back


=head1 CONFIGURATION AND ENVIRONMENT