package main type Segment struct P1 P2 Point func seg Segment Intersec

package main

type Segment struct {
    P1, P2 Point
}

func (seg Segment) Intersects(seg2 Segment) bool {
    vec1 := seg.P2.Dif(seg.P1)
    vec2 := seg2.P2.Dif(seg2.P1)

    cross := vec1.Cross(vec2)

    if cross == 0 {
        return false
    }

    t1 := seg2.P1.Dif(seg.P1).Cross(vec2) / cross
    t2 := seg2.P1.Dif(seg.P1).Cross(vec1) / cross

    return 0 <= t1 && t1 <= 1 && 0 <= t2 && t2 <= 1
}