Function discrete_interval 

pub fn discrete_interval<I: Integer>(a: Interval<I>, b: Interval<I>) -> bool

Discrete intersection test of 1D axis-aligned bounding boxes (intervals).

Shared boundary points will return intersection:

let a = Interval::from_points ( 0, 1);
let b = Interval::from_points (-1, 0);
assert!(discrete_interval (a, b));