Function update

inst/include/Rcpp/S4.h:71–73

* @throw not_s4 if x is not an S4 class */

         * @throw not_s4 if x is not an S4 class
         */
        void update(SEXP x){
            if( ! ::Rf_isS4(x) ) throw not_s4() ;
        }
    } ;

    typedef S4_Impl<PreserveStorage> S4 ;