+ const function_options &opt = registered_functions()[serial];
+
+ if (opt.use_return_type) {
+ // Return type was explicitly specified
+ return opt.return_type;
+ } else {
+ // Default behavior is to use the return type of the first
+ // argument. Thus, exp() of a matrix behaves like a matrix, etc.
+ if (seq.empty())
+ return return_types::commutative;
+ else
+ return seq.begin()->return_type();
+ }