I want to use std::experimental::optional, but MSVS 2013 tells me it can't find the header.
- Why isn't it there?
- Can I roll my own based on code elsewhere? The C++14 proposal maybe?
std::experimental::optional originates from the Boost.Optional library, and this implementation works well in Visual C++ 12.0 (though it differs a little). Reference single-header implementation, based on the N3793 proposal paper, can be found here.
The latest list of supported C++11/14/1z core and library features that are shipped with Visual Studio can be found from the Visual C++ Team blog, from this post in particular. A set of header files of the Standard Library implementation (and some extensions) from Microsoft can be viewed here.
I've found that this implementation compiles with MSVC2013. Note that only compiles, everything else isn't guaranteed.
https://github.com/mapbox/variant/blob/master/include/mapbox/optional.hpp
I was using this one for msvc2015 and it worked:
https://raw.githubusercontent.com/akrzemi1/Optional/master/optional.hpp
来源：https://stackoverflow.com/questions/31474434/no-optional-in-ms-visual-studio-2013-what-to-do