Function rational_derivatives 

pub fn rational_derivatives<P: Blend>(
    knots: &KnotVector,
    control: &[Weighted<P>],
    u: f64,
    n: usize,
    tol: Tolerances,
) -> OgeomResult<Vec<P>>

Evaluate a rational B-spline and its derivatives up to order n.

The quotient rule applied to the homogeneous form. Differentiating the projected curve directly is not an option: the projection is a quotient, so its derivatives mix all lower orders.

Errors

As evaluate_rational.