code: func (ns *Namespace) Log(a interface{}) (float64, error) {
  	af, err := cast.ToFloat64E(a)
  
  	if err != nil {
  		return 0, errors.New("Log operator can't be used with non integer or float value")
  	}
  
  	return math.Log(af), nil
  }
docs: // Log returns the natural logarithm of a number.