pub type szipsc_vft = Option<unsafe extern "C" fn(zeta_r: *mut c_void, zeta_i: *mut c_void, chi: *mut c_void)>;
enum szipsc_vft { None, Some(unsafe extern "C" fn(_: *mut c_void, _: *mut c_void, _: *mut c_void)), }
No value.
Some value of type T.
T