first test for observer code

[scpubgit/DKit.git] / lib / DX / State.pm

diff --git a/lib/DX/State.pm b/lib/DX/State.pm
index 0ee431c..7ec2e1b 100644 (file)
--- a/lib/DX/State.pm
+++ b/lib/DX/State.pm
@@ -1,5 +1,7 @@
 package DX::State;
 
+use Return::MultiLevel qw(with_return);
+use DX::Op::FromCode;
 use Moo;
 
 has next_op => (is => 'ro', required => 1);
@@ -17,11 +19,21 @@ sub scope_var {
   $self->by_id->{$self->scope->{$name}};
 }
 
+sub bind_var_then {
+  my ($self, $var, $value, $then) = @_;
+  warn "Binding ".$var->id." to $value";
+  my $bound = $var->with_value($value);
+  $self->but(
+    by_id => { %{$self->by_id}, $var->id => $bound },
+    next_op => $then
+  );
+}
+
 sub bind_stream_then {
   my ($self, $var, $stream, $then) = @_;
   warn "Binding ".$var->id." to $stream";
   my $bound = $var->with_stream($stream);
-  $self->new(%$self,
+  $self->but(
     by_id => { %{$self->by_id}, $var->id => $bound },
     next_op => $then
   )->mark_choice($bound);
@@ -29,9 +41,7 @@ sub bind_stream_then {
 
 sub mark_choice {
   my ($self, $var) = @_;
-  $self->new(%$self,
-    last_choice => [ $self, $var ]
-  );
+  $self->but(last_choice => [ $self, $var ]);
 }
 
 sub backtrack {
@@ -41,20 +51,53 @@ sub backtrack {
     $var->bound_value; $var->clear_bound_value;
     return $state->mark_choice($var) unless $var->bound_stream->is_exhausted;
   }
-  die "Out of options";
+  $self->return_from_run(undef);
 }
 
 sub then {
   my ($self, $then) = @_;
-  $self->new(%$self, next_op => $then);
+  $self->but(next_op => $then);
+}
+
+sub return_from_run {
+  my (undef, $return) = @_;
+  (our $Nonlocal_Return)->($return);
 }
 
 sub run {
   my ($state) = @_;
-  while (my $op = $state->next_op) {
-    $state = $op->run($state);
+  with_return {
+    my ($return) = @_;
+    local our $Nonlocal_Return = $return;
+    while (my $op = $state->next_op) {
+      $state = $op->run($state);
+    }
+    return $state;
   }
-  return $state;
+}
+
+sub push_backtrack {
+  $_[0]->then(DX::Op::FromCode->new(code => sub { $_[1]->backtrack }));
+}
+
+sub but {
+  my ($self, @but) = @_;
+  $self->new(%$self, @but);
+}
+
+sub pop_return_stack {
+  my ($self) = @_;
+  my @stack = @{$self->return_stack};
+  my $top = pop @stack;
+  $self->but(return_stack => \@stack, next_op => $top);
+}
+
+sub push_return_then {
+  my ($self, $return, $then) = @_;
+  $self->but(
+    return_stack => [ @{$self->return_stack}, $return ],
+    next_op => $then
+  );
 }
 
 1;