pub type VlSvmDcaUpdateFunction = Option<unsafe extern "C" fn(alpha: f64, inner: f64, norm2: f64, label: f64) -> f64>;
pub enum VlSvmDcaUpdateFunction { None, Some(unsafe extern "C" fn(f64, f64, f64, f64) -> f64), }
No value.
Some value of type T.
T