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/ext/std/tuple.hpp> 9 #include <boost/hana/front.hpp> 10 #include <boost/hana/integral_constant.hpp> 11 12 #include <tuple> 13 #include <utility> 14 namespace hana = boost::hana; 15 16 17 template <typename T> cref(T & t)18T const& cref(T& t) { return t; } 19 20 // a non-movable, non-copyable type 21 struct RefOnly { 22 RefOnly() = default; 23 RefOnly(RefOnly const&) = delete; 24 RefOnly(RefOnly&&) = delete; 25 }; 26 27 template <int i> 28 struct RefOnly_i : hana::int_<i> { 29 RefOnly_i() = default; 30 RefOnly_i(RefOnly_i const&) = delete; 31 RefOnly_i(RefOnly_i&&) = delete; 32 }; 33 main()34int main() { 35 std::tuple<RefOnly> t; 36 37 // Make sure that we return the proper reference types from `at`. 38 { 39 RefOnly&& r1 = hana::at_c<0>(std::move(t)); 40 RefOnly& r2 = hana::at_c<0>(t); 41 RefOnly const& r3 = hana::at_c<0>(cref(t)); 42 43 (void)r1; (void)r2; (void)r3; 44 } 45 46 // Make sure we return the proper reference types from `front`. 47 { 48 RefOnly&& r1 = hana::front(std::move(t)); 49 RefOnly& r2 = hana::front(t); 50 RefOnly const& r3 = hana::front(cref(t)); 51 52 (void)r1; (void)r2; (void)r3; 53 } 54 55 // Make sure we return the proper reference types from `back`. 56 { 57 RefOnly&& r1 = hana::back(std::move(t)); 58 RefOnly& r2 = hana::back(t); 59 RefOnly const& r3 = hana::back(cref(t)); 60 61 (void)r1; (void)r2; (void)r3; 62 } 63 64 // Make sure we return the proper reference types from `at_key`. 65 { 66 std::tuple<RefOnly_i<3>> t{}; 67 RefOnly_i<3>& r1 = hana::at_key(t, RefOnly_i<3>{}); 68 RefOnly_i<3> const& r2 = hana::at_key(cref(t), RefOnly_i<3>{}); 69 RefOnly_i<3>&& r3 = hana::at_key(std::move(t), RefOnly_i<3>{}); 70 71 (void)r1; (void)r2; (void)r3; 72 } 73 } 74