package DX::SearchState;
use Types::Standard qw(Maybe);
+use DX::Step::Backtrack;
use DX::Step::InvokeNextPredicate;
use DX::Class;
has alternatives => (is => 'ro', isa => AlternativeList, required => 1);
+has is_solution_state => (is => 'ro', required => 1);
+
+has on_exhaustion_step => (is => 'ro', required => 1);
+
sub next_proposition {
my ($self, $hyp) = @_;
$hyp ||= $self->current_hypothesis;
$class->new(
current_hypothesis => $hyp,
alternatives => [],
- next_step => DX::Step::InvokeNextPredicate->new(
- proposition => $props->members->[0],
- ),
propositions => $props,
+ (@{$props->members}
+ ? (
+ next_step => DX::Step::InvokeNextPredicate->new(
+ proposition => $props->members->[0],
+ ),
+ is_solution_state => 0,
+ )
+ : ( is_solution_state => 1 )
+ ),
+ on_exhaustion_step => undef,
);
}
sub with_one_step {
my ($self) = @_;
- my $hyp = $self->current_hypothesis;
return undef unless my $step = $self->next_step;
- my ($first_alt, @rest_alt) = my @alt = @{$self->alternatives};
- my ($new_hyp, $alt_step) = $step->apply_to($hyp);
- if ($new_hyp) {
- return $self->but(
- current_hypothesis => $new_hyp,
- alternatives => [
- ($alt_step
- ? [ $hyp, $alt_step ]
- : ()),
- @alt
- ],
- next_step => DX::Step::InvokeNextPredicate->new(
- proposition => $self->next_proposition($new_hyp),
- ),
- );
- }
- if ($alt_step) {
- return $self->but(next_step => $alt_step);
- }
- return undef unless $first_alt;
- trace 'search.backtrack.rewind_to' => $first_alt->[1];
- return $self->but(
- current_hypothesis => $first_alt->[0],
- alternatives => \@rest_alt,
- next_step => $first_alt->[1],
- );
-}
-
-sub find_solution {
- my $state = $_[0];
- while ($state and $state->next_proposition) {
- $state = $state->with_one_step;
- }
- trace 'search.solution.hyp' => $state->current_hypothesis if $state;
- return $state;
+ return $step->apply_to($self);
}
sub force_backtrack {
my ($first_alt, @rest_alt) = @{$self->alternatives};
return undef unless $first_alt;
trace 'search.backtrack.forced' => $first_alt->[0];
- return ref($self)->new(
- current_hypothesis => $first_alt->[0],
- next_step => $first_alt->[1],
- alternatives => \@rest_alt,
- propositions => $self->propositions,
- );
-}
-
-sub find_next_solution {
- my ($self) = @_;
- return undef unless my $bt = $self->force_backtrack;
- return $bt->find_solution;
+ return $self->but(
+ next_step => DX::Step::Backtrack->new,
+ )->with_one_step;
}
1;