diff --git a/expression_fwd.hpp b/expression_fwd.hpp
index a7213f6..ca727e1 100644
--- a/expression_fwd.hpp
+++ b/expression_fwd.hpp
@@ -59,6 +59,9 @@ namespace boost::proto17 {
         bitwise_xor_assign, // ^=
         subscript, // []
 
+        // ternary
+        // TODO: if_else, // (analogous to) ?:
+
         // n-ary
         call // ()
     };
diff --git a/user_macros.hpp b/user_macros.hpp
index f2c7bb7..028191f 100644
--- a/user_macros.hpp
+++ b/user_macros.hpp
@@ -275,4 +275,6 @@
         };                                                              \
     }                                                                   \
 
+// TODO: Unary UDT op macro.
+
 #endif