clean up tree root detection

tree.hpp

@@ -24,6 +24,8 @@ struct Tree {
 
 		bool is_leaf() const { return children.size() == 0; }
 
+        bool is_root() const { return parent == nullptr; }
+
 		Node* parent_node() { return parent; }
 
 		Node* create_leaf(const T& item) {

tree_test.cpp

@@ -21,7 +21,7 @@ void test_tree() {
         for(auto i = 0; i < tab_count; ++i)
                 std::printf("\t");
 
-        if(data.empty()) {
+        if(node->is_root()) {
             std::printf("(root)\n");
         } else {
             std::printf("%s\n", data.c_str());

vxorg.cpp

@@ -22,7 +22,7 @@ int main() {
             }
         }
 
-		if(data.name.empty()) {
+		if(node->is_root()) {
 			std::printf("(root)\n");
 		} else {
 			if(data.is_sample) {