Benchmark checking for duplicate types.

test1.cpp

#include<boost/hana.hpp>

namespace hana = boost::hana;

auto list_with_no_dups =
  hana::unpack(
    hana::range_c<int, 0, 50>,
      [](auto... i) {
        return hana::tuple_c<int, i...>;
      });

auto list_with_dups =
  hana::unpack(
    hana::range_c<int, 0, 50>,
      [](auto... i) {
        return hana::tuple_c<int, (i % 10)...>;
      });

template <typename Foldable>
/*constexpr*/ auto has_duplicates(Foldable const& foldable) {
  return hana::unpack(foldable, 
      [&](auto const& ...x) {
          constexpr std::size_t counts[] = {
              decltype(hana::count(foldable, x))::value...
          }; 
        return hana::bool_c<
            hana::detail::find_if(counts, counts + sizeof...(x), hana::_ > 1u)
                !=
            counts + sizeof...(x)
        >;
  }); 
}

int main() {
  BOOST_HANA_CONSTANT_CHECK(!has_duplicates(list_with_no_dups));
  BOOST_HANA_CONSTANT_CHECK(has_duplicates(list_with_dups));
}