+sub elements_to_tree
+{
+ my($self, $elements)=@_;
+ return undef unless(@$elements);
+ my ($left, $right, $op)=(undef, undef, undef);
+ my $thing=pop @$elements;
+ if(ref($thing) eq "ID3FS::PathElement::Boolean")
+ {
+ my $op=$thing;
+ $right=$self->elements_to_tree($elements);
+ if($op->{name} ne "NOT")
+ {
+ $left=$self->elements_to_tree($elements);
+ }
+ return ID3FS::Path::Node->new($left, $op, $right);
+ }
+ else
+ {
+ return ID3FS::Path::Node->new($thing);
+ }
+}
+
+# Dijkstra's shunting-yard algorithm
+sub sort_elements
+{
+ my ($self, @input)=@_;
+ my @opstack=();
+ my @output=();
+# print "INPUT: ", join(', ', map { $_->{name}; } @input), "\n";
+ while(my $thing = shift @input)
+ {
+ if(ref($thing) eq "ID3FS::PathElement::Tag")
+ {
+# print "Pushing $thing->{name} to output\n";
+ push(@output, $thing);
+# print "OPSTACK: ", join(', ', map { $_->{name}; } @opstack), "\n";
+# print "OUTPUT: ", join(', ', map { $_->{name}; } @output), "\n";
+ }
+ elsif(ref($thing) eq "ID3FS::PathElement::Boolean")
+ {
+# print "BOOL: $thing->{name}\n";
+ # bool
+# print "thing: $thing->{name}: $priorities{$thing->{name}} ";
+ if(@opstack)
+ {
+# print("topop: ", $opstack[$#opstack]->{name},
+# ": ", $priorities{$opstack[$#opstack]->{name}}, "\n");
+ }
+ while(@opstack &&
+ ($priorities{$thing->{name}} <= $priorities{$opstack[$#opstack]->{name}}))
+ {
+# print "Pushing ", $opstack[$#opstack]->{name}, " from opstack to output\n";
+ push(@output, pop(@opstack));
+# print "OPSTACK: ", join(', ', map { $_->{name}; } @opstack), "\n";
+# print "OUTPUT: ", join(', ', map { $_->{name}; } @output), "\n";
+ }
+# print "Pushing $thing->{name} to opstack\n";
+ push(@opstack, $thing);
+# print "OPSTACK: ", join(', ', map { $_->{name}; } @opstack), "\n";
+# print "OUTPUT: ", join(', ', map { $_->{name}; } @output), "\n";
+ }
+ }
+ while(@opstack)
+ {
+ push(@output, pop(@opstack));
+ }
+# print "STACK: ", join(', ', map { $_->{name}; } @output), "\n";
+ return @output;
+}
+
+sub used_tags
+{
+ my($self)=@_;
+ print "TAGTREE UNDEF\n" unless(defined($self->{tagtree}));
+ return undef unless(defined($self->{tagtree}));
+ return($self->{tagtree}->used_tags());
+}
+
+sub tag_has_values
+{
+ my($self)=@_;
+ my $tail=$self->{elements}->[$#{$self->{elements}}];
+ if($tail && ref($tail) eq "ID3FS::PathElement::Tag")
+ {
+ return($self->{db}->tag_has_values($tail->{id}));
+ }
+}
+
+sub trailing_tag_id
+{
+ my($self)=@_;
+ my $tail=$self->{elements}->[$#{$self->{elements}}];
+ if($tail && ref($tail) eq "ID3FS::PathElement::Tag")
+ {
+ return($tail->{id});
+ }
+ return undef;
+}
+