Betterness rules on conversions are only applied for arguments that are explicitly given – omitted optional arguments are ignored for betterness purposes.
转换的最优原则只用于明确给定的实参——出于最优的目的,忽略掉的可选参数在重载解析时将不做考虑。
Therefore, the goodness or the betterness of strategies as projections of some future outcomes will never be known for sure until they have been tried.