Function segments_intersect 

pub fn segments_intersect(
    a1x: i64,
    a1y: i64,
    a2x: i64,
    a2y: i64,
    b1x: i64,
    b1y: i64,
    b2x: i64,
    b2y: i64,
) -> bool

True if segments A1→A2 and B1→B2 intersect (proper crossing OR endpoint on segment).