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1 | package DX::SearchState; |
2 | |
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3 | use Types::Standard qw(Maybe); |
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4 | use DX::Step::InvokeNextPredicate; |
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5 | use DX::Class; |
6 | |
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7 | has current_hypothesis => (is => 'ro', isa => Hypothesis, required => 1); |
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8 | |
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9 | has next_step => (is => 'ro', isa => Maybe[Step]); |
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10 | |
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11 | has alternatives => (is => 'ro', isa => AlternativeList, required => 1); |
12 | |
13 | sub new_for { |
14 | my ($class, $hyp) = @_; |
15 | $class->new( |
16 | current_hypothesis => $hyp, |
17 | alternatives => [], |
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18 | next_step => DX::Step::InvokeNextPredicate->new, |
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19 | ); |
20 | } |
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21 | |
22 | sub with_one_step { |
23 | my ($self) = @_; |
24 | my $hyp = $self->current_hypothesis; |
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25 | return undef unless my $step = $self->next_step; |
26 | my ($first_alt, @rest_alt) = my @alt = @{$self->alternatives}; |
27 | my ($new_hyp, $alt_step) = $step->apply_to($hyp); |
28 | if ($new_hyp) { |
29 | return $self->but( |
30 | current_hypothesis => $new_hyp, |
31 | alternatives => [ |
32 | ($alt_step |
33 | ? [ $hyp, $alt_step ] |
34 | : ()), |
35 | @alt |
36 | ], |
37 | next_step => DX::Step::InvokeNextPredicate->new, |
38 | ); |
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39 | } |
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40 | if ($alt_step) { |
41 | return $self->but(next_step => $alt_step); |
42 | } |
43 | return undef unless $first_alt; |
44 | trace 'search.backtrack.rewind_to' => $first_alt->[1]; |
45 | return $self->but( |
46 | current_hypothesis => $first_alt->[0], |
47 | alternatives => \@rest_alt, |
48 | next_step => $first_alt->[1], |
49 | ); |
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50 | } |
51 | |
52 | sub find_solution { |
53 | my $state = $_[0]; |
54 | while ($state and @{$state->current_hypothesis->outstanding_propositions}) { |
55 | $state = $state->with_one_step; |
56 | } |
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57 | trace 'search.solution.hyp' => $state->current_hypothesis if $state; |
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58 | return $state; |
59 | } |
60 | |
61 | sub force_backtrack { |
62 | my ($self) = @_; |
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63 | my ($first_alt, @rest_alt) = @{$self->alternatives}; |
64 | return undef unless $first_alt; |
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65 | trace 'search.backtrack.forced' => $first_alt->[0]; |
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66 | return ref($self)->new( |
67 | current_hypothesis => $first_alt->[0], |
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68 | next_step => $first_alt->[1], |
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69 | alternatives => \@rest_alt |
70 | ); |
71 | } |
72 | |
73 | sub find_next_solution { |
74 | my ($self) = @_; |
75 | return undef unless my $bt = $self->force_backtrack; |
76 | return $bt->find_solution; |
77 | } |
78 | |
79 | 1; |