Something like this works when my destination is a vector:

boost::range::push_back (destV, some_range);

but there doesn't seem to be anything to use when the destination is a set. The obvious

boost::range::insert (destS, some_range);

complains that I don't have enough arguments for insert.

Looking at the implementation in range/algorithm_ext/insert.hpp, it seems like an overloaded function without the "before" argument ought to work on any container that has a .insert(InputIt first, InputIt last ); member function, specifically including std::set and boost::container::flat_set.

Is there some technical reason why this isn't supported? If not, I'd like to see what it takes to get it added.

I agree with you that this would be good to have. In fact, there is an open bug for this [1], with a patch. The patch does not include tests and documentation, however. If you're interested in helping, you could do so by writing the tests and documentation and posting an updated patch. I would be happy to review and commit that. Regards, Nate [1] https://svn.boost.org/trac/boost/ticket/6726