pub type R_altcomplex_Elt_method_t = Option<unsafe extern "C" fn(arg1: SEXP, arg2: R_xlen_t) -> Rcomplex>;
pub enum R_altcomplex_Elt_method_t { None, Some(unsafe extern "C" fn(*mut SEXPREC, isize) -> Rcomplex), }
No value.
Some value of type T.
T