cuda::experimental::stf::exception_policies::when# template<class _Pred, class _P>auto cuda::experimental::stf::exception_policies::when( _Pred &&__pred, _P &&__p )# Restricts a policy with a runtime predicate. Returns when_t{pred} & p: as a | arm, false means the next alternative gets the exception; inside a larger &, false declines the whole sequence.