引用类型的 std::optional 特化

问题描述

为什么std::optional(目前libc++中的std::experimental::optional)没有引用类型的特化(与 boost::optional 相比)?

Why std::optional (std::experimental::optional in libc++ at the moment) does not have specialization for reference types (compared with boost::optional)?

我认为这将是非常有用的选择.

I think it would be very useful option.

在STL中是否有一些对象引用可能已经存在的对象语义?

Is there some object with reference to maybe already existing object semantics in STL?

推荐答案

When n3406(提案的第 2 修订版)进行了讨论，一些委员会成员对可选的参考资料感到不舒服.在 n3527 (修订版 #3)，作者决定将可选引用作为辅助建议，以增加获得批准的可选值并将其放入 C++14 的机会.虽然由于其他各种原因，可选没有完全进入 C++14，但委员会并没有拒绝可选引用，并且如果有人提出它，将来可以自由添加可选引用.

When n3406 (revision #2 of the proposal) was discussed, some committee members were uncomfortable with optional references. In n3527 (revision #3), the authors decided to make optional references an auxiliary proposal, to increase the chances of getting optional values approved and put into what became C++14. While optional didn't quite make it into C++14 for various other reasons, the committee did not reject optional references and is free to add optional references in the future should someone propose it.

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