I'm working on a compiler for one of the courses I need for my degree and I need to modify a major part of it (the expression evaluator) to handle optional references (I could just overload the entire thing but I don't want to duplicate code and create more work for myself). I came across std::reference_wrapper (and its helper functions, std::ref and std::cref). My question is: is it legal and okay to create an std::optional<std::reference_wrapper<T>> as a function parameter (since an std::optional<T&> is illegal)? If I, say, have an std::optional<std::reference_wrapper<std::stringstream>> and I want to write data to it and have that data remain when I return to the caller, would it be fine to use that (std::optional<std::reference_wrapper<std::stringstream>>) when declaring the function, or is this bad practice? Is there some better way I can use (while trying to avoid pointers)?