ceph/src/boost/libs/hana/example/ext/std/integer_sequence/foldable.cpp

   1 // Copyright Louis Dionne 2013-2016
   2 // Distributed under the Boost Software License, Version 1.0.
   3 // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
   4
   5 #include <boost/hana/assert.hpp>
   6 #include <boost/hana/ext/std/integer_sequence.hpp>
   7 #include <boost/hana/unpack.hpp>
   8
   9 #include <tuple>
  10 #include <utility>
  11 namespace hana = boost::hana;
  12
  13
  14 auto add = [](auto a, auto b, auto c) { return a + b + c; };
  15
  16 int main() {
  17     std::tuple<int, long, double> tuple{1, 2l, 3.3};
  18
  19     auto sum = hana::unpack(std::integer_sequence<int, 0, 1, 2>{}, [&](auto ...i) {
  20         // the `i`s are `std::integral_constant<int, ...>`s
  21         return add(std::get<decltype(i)::value>(tuple)...);
  22     });
  23
  24     BOOST_HANA_RUNTIME_CHECK(sum == 6.3);
  25 }