Modern C++ actually makes for a pretty nice prototyping language if you use auto and std::shared_ptr everywhere, turn on RTTI, and make every method virtual. Th

Modern C++ actually makes for a pretty nice prototyping language if you use auto and std::shared_ptr everywhere, turn on RTTI, and make every method virtual. That gives you mostly-hidden compile-time type induction, explicit type-based dispatch, reference-counted garbage collection, and extensible classes. Then, once you've got things working, you can refine the ownership semantics and internal interfaces.