<experimental/optional> is not available anymore in newer STL versions, e.g. according to libc++'s TS deprecation policy: https://libcxx.llvm.org/TS_deprecation.html
<experimental/optional> is not available anymore in newer STL versions, e.g. according to libc++'s TS deprecation policy: https://libcxx.llvm.org/TS_deprecation.html