diff --git a/lib/pddlparse/include/pddlparse/AST.h b/lib/pddlparse/include/pddlparse/AST.h
index 210f982..eceed10 100644
--- a/lib/pddlparse/include/pddlparse/AST.h
+++ b/lib/pddlparse/include/pddlparse/AST.h
@@ -271,6 +271,7 @@ struct And: public NAry<And<Argument>, Argument>
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
+// TODO: make binary expression
 template<class Argument>
 struct At
 {