spatial/r{2,3}: add Norm and Norm2

spatial/r3/vector.go

@@ -4,6 +4,8 @@
 
 package r3
 
+import "math"
+
 // Vec is a 3D vector.
 type Vec struct {
 	X, Y, Z float64
@@ -47,6 +49,18 @@ func (p Vec) Cross(q Vec) Vec {
 	}
 }
 
+// Norm returns the Euclidean norm of p
+//  |p| = sqrt(p_x^2 + p_y^2 + p_z^2).
+func Norm(p Vec) float64 {
+	return math.Hypot(p.X, math.Hypot(p.Y, p.Z))
+}
+
+// Norm returns the Euclidean squared norm of p
+//  |p|^2 = p_x^2 + p_y^2 + p_z^2.
+func Norm2(p Vec) float64 {
+	return p.X*p.X + p.Y*p.Y + p.Z*p.Z
+}
+
 // Box is a 3D bounding box.
 type Box struct {
 	Min, Max Vec