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