From Code to Community: Sponsoring The Perl and Raku Conference 2025 Learn more

MUDLER / Algorithm-SAT-Backtracking-0.13 / lib / Algorithm / SAT / Backtracking / Ordered.pm 

            

              
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
111
112
113
114
115
116
117
118
119
120

              
package Algorithm::SAT::Backtracking::Ordered;
use base 'Algorithm::SAT::Backtracking';
use strict;
use warnings;
use Hash::Ordered;
##Ordered implementation, of course has its costs
our $VERSION = "0.13";
sub _choice {
    my ( undef, $variables, $model ) = @_;
    my $choice;
    foreach my $variable ( @{$variables} ) {
        $choice = $variable and last if ( !$model->exists($variable) );
    }
    return $choice;
}
sub solve {
    my ( $self, $variables, $clauses, $model ) = @_;
    $model = Hash::Ordered->new if !defined $model;
    return $self->SUPER::solve( $variables, $clauses, $model );
}
# ### update
# Copies the model, then sets `choice` = `value` in the model, and returns it, keeping the order of keys.
sub update {
    my ( $self, $copy, $choice, $value ) = @_;
    $copy = $copy->clone;
    $copy->set( $choice => $value );
    return $copy;
}
# ### resolve
# Resolve some variable to its actual value, or undefined.
sub resolve {
    my ( undef, $var, $model ) = @_;
    if ( substr( $var, 0, 1 ) eq "-" ) {
        my $value = $model->get( substr( $var, 1 ) );
        return !defined $value ? undef : $value == 0 ? 1 : 0;
    }
    else {
        return $model->get($var);
    }
}
1;
=encoding utf-8
=head1 NAME
Algorithm::SAT::Backtracking::Ordered - A simple Backtracking SAT ordered implementation
=head1 SYNOPSIS
    # You can use it with Algorithm::SAT::Expression
    use Algorithm::SAT::Expression;
    my $expr = Algorithm::SAT::Expression->new->with("Algorithm::SAT::Backtracking::Ordered");
    $expr->or( '-foo@2.1', 'bar@2.2' );
    $expr->or( '-foo@2.3', 'bar@2.2' );
    $expr->or( '-baz@2.3', 'bar@2.3' );
    $expr->or( '-baz@1.2', 'bar@2.2' );
    my $model = $exp->solve();
    # Or you can use it directly:
    use Algorithm::SAT::Backtracking::Ordered;
    my $solver = Algorithm::SAT::Backtracking::Ordered->new;
    my $variables = [ 'blue', 'green', 'yellow', 'pink', 'purple' ];
    my $clauses = [
        [ 'blue',  'green',  '-yellow' ],
        [ '-blue', '-green', 'yellow' ],
        [ 'pink', 'purple', 'green', 'blue', '-yellow' ]
    ];
    my $model = $solver->solve( $variables, $clauses );
=head1 DESCRIPTION
Algorithm::SAT::Backtracking::Ordered is a pure Perl implementation of a simple SAT Backtracking solver, in this variant of L<Algorithm::SAT::Backtracking> we keep the order of the model updates and return a L<Hash::Ordered> as result.
Look at L<Algorithm::SAT::Backtracking> for a theory description.
Look also at the test file for an example of usage.
L<Algorithm::SAT::Expression> use this module to solve Boolean expressions.
=head1 METHODS
Inherits all the methods from L<Algorithm::SAT::Backtracking::DPLL> and override/implements the following:
=head2 SOLVE
    $expr->solve();
in this case returns a L<Hash::Ordered>.
=head1 LICENSE
Copyright (C) mudler.
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.
=head1 AUTHOR
mudler E<lt>mudler@dark-lab.netE<gt>
=head1 SEE ALSO
L<Algorithm::SAT::Expression>, L<Algorithm::SAT::Backtracking::DPLL>, L<Algorithm::SAT::Backtracking>, L<Algorithm::SAT::Backtracking::Ordered::DPLL>
=cut