| 1 | // Copyright Louis Dionne 2013-2022 |
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| 2 | // Distributed under the Boost Software License, Version 1.0. |
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| 3 | // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) |
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| 4 | |
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| 5 | #include <boost/hana/assert.hpp> |
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| 6 | #include <boost/hana/chain.hpp> |
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| 7 | #include <boost/hana/equal.hpp> |
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| 8 | #include <boost/hana/for_each.hpp> |
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| 9 | #include <boost/hana/traits.hpp> |
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| 10 | #include <boost/hana/tuple.hpp> |
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| 11 | #include <boost/hana/type.hpp> |
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| 12 | |
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| 13 | #include <type_traits> |
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| 14 | #include <utility> |
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| 15 | namespace hana = boost::hana; |
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| 16 | |
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| 17 | |
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| 18 | // Using the `tuple` Monad, we generate all the possible combinations of |
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| 19 | // cv-qualifiers and reference qualifiers. Then, we use the `optional` |
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| 20 | // Monad to make sure that our generic function can be called with |
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| 21 | // arguments of any of those types. |
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| 22 | |
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| 23 | // cv_qualifiers : type -> tuple(type) |
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| 24 | auto cv_qualifiers = [](auto t) { |
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| 25 | return hana::make_tuple( |
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| 26 | t, |
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| 27 | hana::traits::add_const(t), |
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| 28 | hana::traits::add_volatile(t), |
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| 29 | hana::traits::add_volatile(hana::traits::add_const(t)) |
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| 30 | ); |
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| 31 | }; |
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| 32 | |
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| 33 | // ref_qualifiers : type -> tuple(type) |
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| 34 | auto ref_qualifiers = [](auto t) { |
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| 35 | return hana::make_tuple( |
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| 36 | hana::traits::add_lvalue_reference(t), |
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| 37 | hana::traits::add_rvalue_reference(t) |
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| 38 | ); |
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| 39 | }; |
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| 40 | |
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| 41 | auto possible_args = cv_qualifiers(hana::type_c<int>) | ref_qualifiers; |
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| 42 | |
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| 43 | BOOST_HANA_CONSTANT_CHECK( |
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| 44 | possible_args == hana::make_tuple( |
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| 45 | hana::type_c<int&>, |
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| 46 | hana::type_c<int&&>, |
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| 47 | hana::type_c<int const&>, |
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| 48 | hana::type_c<int const&&>, |
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| 49 | hana::type_c<int volatile&>, |
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| 50 | hana::type_c<int volatile&&>, |
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| 51 | hana::type_c<int const volatile&>, |
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| 52 | hana::type_c<int const volatile&&> |
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| 53 | ) |
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| 54 | ); |
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| 55 | |
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| 56 | struct some_function { |
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| 57 | template <typename T> |
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| 58 | void operator()(T&&) const { } |
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| 59 | }; |
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| 60 | |
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| 61 | int main() { |
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| 62 | hana::for_each(possible_args, [](auto t) { |
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| 63 | using T = typename decltype(t)::type; |
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| 64 | static_assert(decltype(hana::is_valid(some_function{})(std::declval<T>())){}, |
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| 65 | "some_function should be callable with any type of argument" ); |
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| 66 | }); |
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| 67 | } |
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| 68 | |
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