rem: ARTS_INTERFACE* clone(void) const { std::cerr << "Not implemented!" << std::endl; return 0; }
add: ARTS_INTERFACE* ARTS_INTERFACE::clone(void) const { ARTS_INTERFACE* target = new ARTS_INTERFACE(); for(int n = 0; n < number_of_params(); n++) { target->set_parameter(n + 1, get_parameter(n + 1)); } return(target); }
context:   ARTS_INTERFACE* clone(void) const { std::cerr << "Not implemented!" << std::endl; return 0; }