The second piece (uniform call syntax) looks convenient, though I don’t see a realistic way to integrate it into modern C++. The first (structural pattern matching) is, for me, more of a dividing line between low- and high-level languages. I tend to avoid it in my C++, just as I avoid inheritance, virtual functions, and exceptions… or `<functional>` header contents.

Still, it’s always fun to stumble on corners of the STL I’d never paid attention to, even if I won’t end up using them. Thought it was worth sharing :)