ceph/src/boost/libs/hana/example/optional/sfinae.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/equal.hpp>
   8 #include <boost/hana/optional.hpp>
   9 namespace hana = boost::hana;
  10
  11
  12 int main() {
  13     BOOST_HANA_CONSTEXPR_LAMBDA auto incr = [](auto x) -> decltype(x + 1) {
  14         return x + 1;
  15     };
  16
  17     BOOST_HANA_CONSTEXPR_CHECK(hana::sfinae(incr)(1) == hana::just(2));
  18
  19     struct invalid { };
  20     BOOST_HANA_CONSTANT_CHECK(hana::sfinae(incr)(invalid{}) == hana::nothing);
  21 }