func (v Vec) Len() float64 {
	return float64(math.Hypot(float64(v.X), float64(v.Y)))
}
func (v Vec) Len() float64 {
	return float64(math.Hypot(float64(v.X), float64(v.Y)))
}
func ( v Vec ) Len ( ) float64 { return float64 ( math . Hypot ( float64 ( v . X ) , float64 ( v . Y ) ) ) }
// Len returns the vector's length.
Len returns the vector s length .