pub type optimgr = Option<unsafe extern "C" fn(arg1: c_int, arg2: *mut f64, arg3: *mut f64, arg4: *mut c_void)>;
enum optimgr { None, Some(unsafe extern "C" fn(_: i32, _: *mut f64, _: *mut f64, _: *mut c_void)), }
No value.
Some value of type T.
T