Segment Intersection

segment_intersection.kt

// https://bryceboe.com/2006/10/23/line-segment-intersection-algorithm/

fun main(args: Array<String>) {

    val x1 = Point(0.0, 0.0)
    val y1 = Point(4.0, 4.0)

    val x2 = Point(0.0, 4.0)
    val y2 = Point(4.0, 0.0)

    println(intersect(x1,y1,x2,y2))

}

data class Point(val x: Double, val y: Double)

data class Segment(val start: Point, val end: Point)

fun ccw(a: Point, b: Point, c: Point) =
        (c.y - a.y) * (b.x - a.x) > (b.y - a.y) * (c.x - a.x)

fun intersect(x1: Point, y1: Point, x2: Point, y2: Point) =
        ccw(x1,x2,y2) !=  ccw(y1,x2,y2) && ccw(x1,y1,x2) != ccw(x1,y1,y2)

fun intersect(segment1: Segment, segment2: Segment) = 
        intersect(segment1.start, segment1.end, segment2.start, segment2.end)