v.which() will return the 0-based index of the type of the object currently held. When you are retrieving the object your code must use a static type (in order to satisfy the get<T> function template) to refer to an (effectively) dynamically typed object. You need to either test for the type (using which() or type()) … Read more
clang is correct here. Here’s a reduced example: struct B { protected: B() { } }; struct D : B { }; auto d = D{}; In C++14, D is not an aggregate because it has a base class, so D{} is “normal” (non-aggregate) initialization which invokes D‘s default constructor, which in turn invokes B‘s … Read more
Have you looked at the comparison in the variant library already? (Not sure what states from external sources are, so it’s kind of hard to say what’s more appropriate for you.)
If you read the boost::any documentation they provide the source for the idea: http://www.two-sdg.demon.co.uk/curbralan/papers/ValuedConversions.pdf It’s basic information hiding, an essential C++ skill to have. Learn it! Since the highest voted answer here is totally incorrect, and I have my doubts that people will actually go look at the source to verify that fact, here’s a … Read more