reseatable_reference

        template
        <
          typename Type
        >
        class ReseatableReference
        {
          public:
          ReseatableReference ( const Type& reference ) : reference( reference ) {};
          void set( const Type& reference ) { ~ReseatableReference(); new (this) ReseatableReference( reference ); }
          Type& operator()() { return reference; };
          operator Type&() { return reference; };
          const Type& reference;
        };