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/at.hpp> 6 #include <boost/hana/at_key.hpp> 7 #include <boost/hana/back.hpp> 8 #include <boost/hana/front.hpp> 9 #include <boost/hana/integral_constant.hpp> 10 #include <boost/hana/tuple.hpp> 11 12 #include <utility> 13 namespace hana = boost::hana; 14 15 16 template <typename T> cref(T & t)17T const& cref(T& t) { return t; } 18 19 // a non-movable, non-copyable type 20 struct RefOnly { 21 RefOnly() = default; 22 RefOnly(RefOnly const&) = delete; 23 RefOnly(RefOnly&&) = delete; 24 }; 25 26 template <int i> 27 struct RefOnly_i : hana::int_<i> { 28 RefOnly_i() = default; 29 RefOnly_i(RefOnly_i const&) = delete; 30 RefOnly_i(RefOnly_i&&) = delete; 31 }; 32 main()33int main() { 34 hana::tuple<RefOnly> t; 35 36 // Make sure that we return the proper reference types from `at`. 37 { 38 RefOnly&& r1 = hana::at_c<0>(std::move(t)); 39 RefOnly& r2 = hana::at_c<0>(t); 40 RefOnly const& r3 = hana::at_c<0>(cref(t)); 41 42 (void)r1; (void)r2; (void)r3; 43 } 44 45 // Make sure we return the proper reference types from `front`. 46 { 47 RefOnly&& r1 = hana::front(std::move(t)); 48 RefOnly& r2 = hana::front(t); 49 RefOnly const& r3 = hana::front(cref(t)); 50 51 (void)r1; (void)r2; (void)r3; 52 } 53 54 // Make sure we return the proper reference types from `back`. 55 { 56 RefOnly&& r1 = hana::back(std::move(t)); 57 RefOnly& r2 = hana::back(t); 58 RefOnly const& r3 = hana::back(cref(t)); 59 60 (void)r1; (void)r2; (void)r3; 61 } 62 63 // Make sure we return the proper reference types from `at_key`. 64 { 65 hana::tuple<RefOnly_i<3>> t{}; 66 RefOnly_i<3>& r1 = hana::at_key(t, RefOnly_i<3>{}); 67 RefOnly_i<3> const& r2 = hana::at_key(cref(t), RefOnly_i<3>{}); 68 RefOnly_i<3>&& r3 = hana::at_key(std::move(t), RefOnly_i<3>{}); 69 70 (void)r1; (void)r2; (void)r3; 71 } 72 } 73