Why Does `std::optional` Lack Reference Type Specializations?

Question: Exploring the Absence of Reference Type Specializations in std::optional

In standard C , std::optional provides a container to hold a value or indicate its absence. However, unlike its counterpart in Boost, std::optional lacks specializations for reference types, leaving users with a question: why? This article delves into the reasons behind this design decision and explores alternative options available in the standard library to handle references to optional values.

Answer: Addressing Concerns and Future Prospects

During the initial proposal (n3406) for optional values, concerns were raised by committee members regarding optional references. Subsequently, in n3527, the authors proposed separating optional references into an auxiliary proposal to enhance the chances of adoption for optional values.

While optional references were not included in C 14 due to other factors, they were not rejected by the committee. This leaves open the possibility of incorporating optional references into a future C standard should a proposal be submitted.

Alternatives for Referencing Optional Values

Despite the absence of std::optional specialization for reference types, the standard library does provide an alternative for referencing optional values:

• std::reference_wrapper<:optional>>: This allows you to create a reference to an optional value, ensuring that changes made to the optional value will be reflected in the reference. However, it is important to note that the optional value remains immutable if the reference is a constant reference (i.e., initialized with std::cref).

In conclusion, the lack of reference type specializations in std::optional stemmed from concerns during the proposal process. However, the committee remains open to considering optional references in the future. Additionally, the standard library provides std::reference_wrapper<:optional>> as an alternative for referencing optional values in the interim.

The above is the detailed content of Why Does `std::optional` Lack Reference Type Specializations?. For more information, please follow other related articles on the PHP Chinese website!