code: func Vectorize(f func(float64) float64) func(xs []float64) []float64 {
  	return func(xs []float64) []float64 {
  		return Map(f, xs)
  	}
  }
docs: // Vectorize returns a function g(xs) that applies f to each x in xs.
  //
  // f may be evaluated in parallel and in any order.