Function robust::orient2d

pub fn orient2d<T: Into<f64>>(pa: Coord<T>, pb: Coord<T>, pc: Coord<T>) -> f64

Returns a positive value if the coordinates pa, pb, and pc occur in counterclockwise order (pc lies to the left of the directed line defined by coordinates pa and pb).
Returns a negative value if they occur in clockwise order (pc lies to the right of the directed line pa, pb).
Returns 0 if they are collinear.