| 1 | // Copyright Louis Dionne 2013-2022 |
|---|---|
| 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/not.hpp> |
| 7 | #include <boost/hana/type.hpp> |
| 8 | |
| 9 | #include <string> |
| 10 | #include <vector> |
| 11 | namespace hana = boost::hana; |
| 12 | |
| 13 | |
| 14 | int main() { |
| 15 | // Checking for a member |
| 16 | struct Person { std::string name; }; |
| 17 | auto has_name = hana::is_valid([](auto&& p) -> decltype((void)p.name) { }); |
| 18 | |
| 19 | Person joe{.name: "Joe"}; |
| 20 | static_assert(has_name(joe), ""); |
| 21 | static_assert(!has_name(1), ""); |
| 22 | |
| 23 | |
| 24 | // Checking for a nested type |
| 25 | auto has_value_type = hana::is_valid([](auto t) -> hana::type< |
| 26 | typename decltype(t)::type::value_type |
| 27 | > { }); |
| 28 | |
| 29 | static_assert(has_value_type(hana::type_c<std::vector<int>>), ""); |
| 30 | static_assert(!has_value_type(hana::type_c<Person>), ""); |
| 31 | } |
| 32 |