code: func StrToFloat(sc *variable.StatementContext, str string) (float64, error) {
  	str = strings.TrimSpace(str)
  	validStr, err := getValidFloatPrefix(sc, str)
  	f, err1 := strconv.ParseFloat(validStr, 64)
  	if err1 != nil {
  		return f, errors.Trace(err1)
  	}
  	return f, errors.Trace(err)
  }
docs: // StrToFloat converts a string to a float64 at the best-effort.