functions to determine if point is on line

also includes lineOnLine to determine if a line is on another line.
Added a new type line struct which consists of two points.

point.go

@@ -6,6 +6,28 @@ type Point struct {
 	X, Y float64
 }
 
+type line struct {
+	pt1, pt2 Point
+}
+
 func distance(p1, p2 Point) float64 {
 	return math.Sqrt(math.Pow((p1.X-p2.X), 2) + math.Pow((p1.Y-p2.Y), 2))
 }
+
+func onLine(rp1, rp2, p Point) bool {
+	if distance(rp1, p)+distance(rp2, p) == distance(rp1, rp2) {
+		minx, maxx := math.Min(rp1.X, rp2.X), math.Max(rp1.X, rp2.X)
+		miny, maxy := math.Min(rp1.Y, rp2.Y), math.Max(rp1.Y, rp2.Y)
+		if minx <= p.X && p.X <= maxx && miny <= p.Y && p.Y <= maxy {
+			return true
+		}
+	}
+	return false
+}
+
+func lineOnLine(l1, l2 line) bool {
+	if onLine(l1.pt1, l1.pt2, l2.pt1) && onLine(l1.pt1, l1.pt2, l2.pt2) {
+		return true
+	}
+	return false
+}