I got compilation error with Xcode built in compiler, i.e. clang. Using C++17 dialect. <img width="1278" alt="screenshot 2018-03-15 15 07 24" src="https://user-images.githubusercontent.com/110199/37471994-e3e5d5aa-2862-11e8-94ad-a7482e831ebf.png">
I got compilation error with Xcode built in compiler, i.e. clang. Using C++17 dialect.
