ceph/src/boost/libs/hana/example/core/convert/to.cpp

   1 // Copyright Louis Dionne 2013-2017
   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/config.hpp>
   7 #include <boost/hana/core/to.hpp>
   8 #include <boost/hana/equal.hpp>
   9 #include <boost/hana/tuple.hpp>
  10 namespace hana = boost::hana;
  11
  12
  13 template <typename X, typename Y, typename Z>
  14 struct Triple {
  15     X first;
  16     Y second;
  17     Z third;
  18 };
  19
  20 BOOST_HANA_CONSTEXPR_LAMBDA auto triple = [](auto x, auto y, auto z) {
  21     return Triple<decltype(x), decltype(y), decltype(z)>{x, y, z};
  22 };
  23
  24 namespace boost { namespace hana {
  25     template <typename X, typename Y, typename Z>
  26     struct to_impl<tuple_tag, Triple<X, Y, Z>> {
  27         static constexpr auto apply(Triple<X, Y, Z> xs) {
  28             return make_tuple(xs.first, xs.second, xs.third);
  29         }
  30     };
  31 }}
  32
  33 int main() {
  34     BOOST_HANA_CONSTEXPR_CHECK(
  35         hana::to<hana::tuple_tag>(triple(1, '2', 3.3)) == hana::make_tuple(1, '2', 3.3)
  36     );
  37 }