Eric Niebler <eniebler <at> boost.org> writes:
On 3/20/2015 11:44 AM, Louis Dionne wrote:
As a simple curiosity, here's how this could be implemented with Hana: <snip>
And using Meta:
[...]
Eric, abstracting the sort into an `indexed_sort` (meta)function is a great idea. Here's an updated version: ------------------------------------------------------------------------------ #include <boost/hana/integral_constant.hpp> #include <boost/hana/pair.hpp> #include <boost/hana/range.hpp> #include <boost/hana/tuple.hpp> #include <boost/hana/type.hpp> using namespace boost::hana; using namespace boost::hana::literals; auto indexed_sort = [](auto list, auto predicate) { auto indexed_list = zip(list, to<Tuple>(range(0_c, size(list)))); auto sorted = sort_by(predicate, indexed_list); return make_pair(transform(sorted, head), transform(sorted, last)); }; int main() { auto types = tuple_t<char[4], char[2], char[1], char[5], char[3]>; auto sorted = indexed_sort(types, [](auto t, auto u) { return sizeof_(t[0_c]) < sizeof_(u[0_c]); }); using Tup = decltype(unpack(first(sorted), template_<_tuple>))::type; auto indices = second(sorted); Tup tup; char(&a)[3] = tup[indices[0_c]]; char(&b)[2] = tup[indices[1_c]]; char(&c)[5] = tup[indices[2_c]]; } ------------------------------------------------------------------------------
FWIW, these indices don't seem all that useful to me. What exactly was the desired behavior?
No idea :-) Louis