Moved child pointers to OperatorNode class

* access was restricted by declaring them private and offering member methods such as "hasChildren"
* only OperatorNode instances have children, there is no reason for wasting space by keeping empty pointers around in all other instances
* this enabled the removal of all nullptr comparisons from tree construction
* changed "Tree::addNode" factory method template to return a pointer to the type of the constructed node instance instead of a plain node pointer

1 files changed, 2 insertions, 2 deletions

diff --git a/src/tree.h b/src/tree.h
index e2eb7a6..1b673a2 100644
--- a/src/tree.h
+++ b/src/tree.h
@@ -18,8 +18,8 @@ class Tree {
 		std::string print() const;
 
 	private:
-		template <class NodeType, typename... Args>
-		Node* addNode(Args&&... args);
+		template <class Type, typename... Args>
+		typename std::add_pointer<Type>::type addNode(Args&&... args);
 
 		Node* buildTree(const std::string&);