Function residue 

pub fn residue(
    f: impl Fn(Complex) -> Complex,
    pole: Complex,
    order: usize,
) -> Complex

Compute the residue of f at a (simple or higher-order) pole.

For a pole of order order at pole, the residue is estimated numerically by computing the Laurent coefficient via a small circle contour of radius ε. For a simple pole this equals lim_{z→pole} (z − pole) · f(z).

Arguments

• f - meromorphic function
• pole - location of the pole
• order - order of the pole (≥ 1)

Returns

Numerical approximation of the residue.