C++ boost variant question

Answer 1

It is indeed possible, Variant::types meets the requirement of a Mpl.Sequence type and therefore can be queried like any sequence.

Therefore, using boost::mpl::contains from here:

// using C++0x syntax to demonstrate what CONDITION should be replaced with
template <typename T>
using Condition = boost::mpl::contains<Variant::types,T>

Nothing simpler, when you know about it ;)

The full MPL Manual is available in HTML format, should you need some more algorithms.