Function spread 

pub fn spread(
    front: &[Vec<f64>],
    extremes: &[Vec<f64>],
) -> Result<f64, IndicatorError>

Generalized Deb spread using nearest-neighbor Euclidean distances and explicit extreme points. Zero is perfectly even; larger is less uniform.

Errors

Returns an IndicatorError for invalid/inconsistent sets or fewer than two front points.