What is the boost equivalent to std::optional nullopt?

Question

I've imported some code pieces from a third party project into my C++11 project. The third party project uses optional-lite [1], though I'm using Boost heavily in the project and want to keep dependency on other libraries low.

There is boost::optional, but unlike the c++17 counterpart it does not have nullopt.

What's the Boost equivalent to nullopt?

(Note: Boost version is 1.69)

[1] https://github.com/martinmoene/optional-lite

Answer 1

The equivalent is boost::none. See optional(none_t).