There is now a sandbox directory for variadic templates: https://svn.boost.org/trac/boost/browser/sandbox/variadic_templates The tests in variadic_templates/libs/mpl/test/Jamfile have all passed. Some of those tests have been slightly modified to accommodate the variadic template version of mpl sequences. BTW, it's important to apply the gcc patch mentioned here: https://svn.boost.org/trac/boost/browser/sandbox/variadic_templates/README.c... All sequences have been changed to use a new template: foldr_pack whose last argument is a parameter pack. That change also required a new binary template for each sequence: X_item_fold where X is one of: v l s m One reason for that change was to highlight the similarites of the sequences. Some other fold additions were: foldr_iter.hpp foldl_iter.hpp The foldr and foldl correspond roughly to iter_fold and reverse_iter_fold (or the other way around, I can't remember which). The reason for these additions is that they reflect more closely the way foldr and foldl are done in haskell, as indicated by the comments in the .hpp files. One useful application of the pattern expansion mentioned in section 3.6.1 of: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2242.pdf is their use to easily define SEQ_c in terms of SEQ, where SEQ is any sequence. For example: template < typename Integral , Integral... Values
struct list_c : list < integral_c<Integral,Values>... > { typedef Integral value_type; }; Another addition is package_range_c.hpp which can be used to do something similar to range_c. The main motivation for this was the make_indexes on p. 16 of: http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2006/n2080.pdf It was used in a prototype tuple implementation in: variadic_templates/libs/mpl/sandbox/tuple_non_recur.package_range_c.cpp Package_range_c was also useful in the implementation of unpack_args. A really interesting application of these pattern expansions might be another implementation of the cross_product template: http://www.crystalclearsoftware.com/cgi-bin/boost_wiki/wiki.pl?CPPTM_Answers... The reason I think it would be useful is because the expansion of: integral_c<Integral,Values>... results in: integral_c<Integral,Value1> integral_c<Integral,Value2> ... integral_c<Integral,ValueN> where ValueI is the i-th element in Values... Now this is a cross product of a single element, Integral, with each element in Values...; hence, I would think that it would be a simple matter to just repeat this for any number of elements. IOW, instead of integral_c, there could be: template<typename Left, typename...Rights> struct pair_rights : pair<Left,Rights>... {}; and then that, somehow, could be done for each element in some list of Left's. Would somebody like to try this? Hope somebody else finds this useful. -regards, Larry