switch SearchState to using Backtrack step

[scpubgit/DX.git] / lib / DX / SearchState.pm

diff --git a/lib/DX/SearchState.pm b/lib/DX/SearchState.pm
index d119d9b..99ac3f2 100644 (file)
--- a/lib/DX/SearchState.pm
+++ b/lib/DX/SearchState.pm
@@ -1,6 +1,7 @@
 package DX::SearchState;
 
 use Types::Standard qw(Maybe);
+use DX::Step::Backtrack;
 use DX::Step::InvokeNextPredicate;
 use DX::Class;
 
@@ -36,32 +37,13 @@ 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_ss, $alt_step) = $step->apply_to($self);
-  my $new_hyp = ($new_ss ? $new_ss->current_hypothesis : undef);
-  if ($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 => $alt_step);
-  }
+  my ($new_ss) = $step->apply_to($self);
+  return $new_ss if $new_ss;
+  my ($first_alt, @rest_alt) = @{$self->alternatives};
   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],
+    next_step => DX::Step::Backtrack->new,
   );
 }