grammar refactoring: build_visitor fixed & visitors tested

include/parse_tree.hpp

@@ -45,7 +45,7 @@ public:
     std::string GetValue() { // from source
       size_t start = ts_node_start_byte(node_);
       size_t end = ts_node_end_byte(node_);
-      return source_->substr(start, end - start); // TODO check
+      return source_->substr(start, end - start);
     }
 
     bool IsNull() {
@@ -86,28 +86,18 @@ public:
       return Node(ts_node_child_by_field_name(node_, name.c_str(), name.size()), source_);
     }
 
-    // ?? use field id instaed of name ??
-    // ?? node equality check needed ??
+    Node NextSibling() {
+      return Node(ts_node_next_sibling(node_), source_);
+    }
+
+    Node NextNamedSibling() {
+      return Node(ts_node_next_named_sibling(node_), source_);
+    }
   private:
     bool uninitialized_;
     TSNode node_;
     const std::string* source_;
   };
-  class Cursor { // ?? needed ??
-  public:
-    Cursor(const Node& node);
-
-    void ResetTo(const Node& node);
-
-    Node GetCurrentNode();
-    std::string GetCurrentNodeName();
-
-    bool GoToParent();
-    bool GoToNextSibling();
-    bool GoToFirstChild();
-  private:
-    TSTreeCursor cursor_;
-  };
 
   ParseTree(const std::string& source) : source_(source) {
     TSParser* parser = ts_parser_new();