Hi, I'm using boost::variant<> while parsing an input file to create a AST. The example at: http://www.boost.org/doc/libs/1_39_0/doc/html/variant/tutorial.html#variant.... does something very similar. However, it seems that the example usage of boost::recursive_wrapper<> is inefficient, not because of the wrapper itself, but because the creation of a tree of variants becomes more and more costly as that tree grows. The attached example is similar to the tutorial. Creating a nested tree 10,000 deep (with no branching) causes more than 100,000,000 copy-constructions. I.e. since there's no move-awareness, for each single leaf that gets added to the tree we end up creating a new node, adding the leaf to it, then recursively copying over the entire sub-tree up to that point. Creating a move-constructor for the variant type didn't do any good (it was never invoked). But several discussions online (including notes from the original review) imply that boost::variant<> is move-aware. Is this the case? If so, does anyone know how I can get move semantics working using boost::recursive_wrapper<>? I also tried changing the variant type(s) to std::unique_ptr<> rather than boost::recursive_wrapper<>, but that didn't work either (build errors due to non-copyability, specifically in "variant/variant.hpp":404). This is Boost 1.39, and I'm building with GCC 4.4 in C++0x mode. Thanks for the help! -- Matthew L. Creech