1 files changed, 1 insertions, 0 deletions
diff --git a/src/tree.h b/src/tree.h
index 5beec87..f20f765 100644
--- a/src/tree.h
+++ b/src/tree.h
@@ -18,6 +18,7 @@ class Tree {
 
 	private:
 		Node* addOperand(Node**, double);
+		Node* addOperand(Node**, std::string);
 		Node* addOperator(Node**, char);
 		Node* buildTree(std::string);