1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
|
package TComparable;
use strict;
use warnings;
our $VERSION = '0.31';
## we are a trait
use Class::Trait 'base';
use Class::Trait qw(TEquality);
## overload operator
our %OVERLOADS = ( '<=>' => "compare" );
## requires methods
our @REQUIRES = qw(compare);
### methods
# The equals method is there to provide
# specific handler for the '==' operator (and
# to be sure about how '!=' will react, we
# override the autogeneration with the _notEquals
# method).
# This is here so that one can deal with '==' and '!='
# and not the '<', '<=', '<=>', '=>', '>' operators.
# NOTE:
# Our default implementation of equals actually defers
# to the compare method, and the _notEquals method
# actually defers to the value of equals (and returns
# the inverse), so that an object which wants all
# the operators ('<=>' and co.) will be able to use
# the '==' and '!=' operators without an issue.
# If however compare is not defined, a
# MethodNotImplemented exception will be thrown.
# This retains backwards compatability while still
# allowing for specialization.
sub equalTo {
my ( $left, $right ) = @_;
return ( $left->compare($right) == 0 ) ? 1 : 0;
}
1;
__END__
=head1 NAME
TComparable - Trait for adding comparison abilities to your object
=head1 DESCRIPTION
This trait gives your object a wide range of comparison abilities through its
overloading of the E<lt>=E<gt> operator.
=head1 SUB-TRAITS
=over 4
=item B<TEquality>
=back
=head1 REQUIRES
=over 4
=item B<compare ($left, $right)>
This method should return -1 if C<$left> is less than C<$right>, 0 if C<$left>
is equal to C<$right>, and 1 if C<$left> is greater than C<$right>.
=back
=head1 OVERLOADS
=over 4
=item B<E<lt>=E<gt>>
=back
=head1 PROVIDES
=over 4
=item B<equalTo ($left, $right)>
This fufills the requirement of the sub-trait TEquality.
=back
=head1 AUTHOR
Stevan Little E<lt>stevan@iinteractive.comE<gt>
=head1 COPYRIGHT AND LICENSE
Copyright 2004, 2005 by Infinity Interactive, Inc.
L<http://www.iinteractive.com>
This library is free software; you can redistribute it and/or modify it under
the same terms as Perl itself.
=cut
|
