[GFK_of_xmaspast]

> I am pretty lenient, and would go for anything that resembles a compiler-enforced tagged union

http://www.boost.org/doc/libs/1_60_0/doc/html/variant.html ??? (and I think it's supposed to be coming in c++17)

[eru]

That's interesting, thanks! It seems this one discriminates the different possibilities by type, and not by some extra tag (like the constructor in Haskell's ADTs). I wonder how that works, if you want to write something like the `either' function (or even just write down its type in C++):

    either :: (a -> c) -> (b -> c) -> Either a b -> c