function.cpp

template<class ReturnType, class...Xs>
class Function<ReturnType(Xs...)> {
  std::shared_ptr<Concept<ReturnType,Xs...>> pimpl;
  
public:
  Function() {}

  template<class F>
  Function(F const& f)
    : pimpl(new SFModel<F, ReturnType, Xs...> ) // heap allocation
  {}
 
  ~Function() = default;
};