extract backtrack decisions out into steps

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

diff --git a/lib/DX/SearchState.pm b/lib/DX/SearchState.pm
index 005aa3c..18979e7 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;
 
@@ -34,30 +35,8 @@ sub new_for {
 
 sub with_one_step {
   my ($self) = @_;
-  my $hyp = $self->current_hypothesis;
   return undef unless my $step = $self->next_step;
-  my ($new_ss, $alt_step) = $step->apply_to($self);
-  if ($new_ss) {
-    return $new_ss->but(
-      alternatives => [
-        ($alt_step
-          ? [ $hyp, $alt_step ]
-          : ()),
-        @{$new_ss->alternatives}
-      ],
-    );
-  }
-  if ($alt_step) {
-    return $self->but(next_step => $alt_step);
-  }
-  my ($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],
-  );
+  return $step->apply_to($self);
 }
 
 sub force_backtrack {