pub fn triangulate_list_hashed<'a, T, R>(
    points: &'a [Point<T>],
    order: &'a [PointId],
    rng: R
) -> impl Iterator<Item = (PointId, PointId, PointId)> + 'a where
    T: PolygonScalar + ZHashable,
    R: Rng + 'static,