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68 lines
2.1 KiB
C++
68 lines
2.1 KiB
C++
// Copyright Louis Dionne 2013-2022
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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#include <boost/hana/assert.hpp>
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#include <boost/hana/chain.hpp>
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#include <boost/hana/equal.hpp>
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#include <boost/hana/for_each.hpp>
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#include <boost/hana/traits.hpp>
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#include <boost/hana/tuple.hpp>
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#include <boost/hana/type.hpp>
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#include <type_traits>
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#include <utility>
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namespace hana = boost::hana;
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// Using the `tuple` Monad, we generate all the possible combinations of
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// cv-qualifiers and reference qualifiers. Then, we use the `optional`
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// Monad to make sure that our generic function can be called with
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// arguments of any of those types.
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// cv_qualifiers : type -> tuple(type)
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auto cv_qualifiers = [](auto t) {
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return hana::make_tuple(
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t,
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hana::traits::add_const(t),
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hana::traits::add_volatile(t),
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hana::traits::add_volatile(hana::traits::add_const(t))
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);
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};
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// ref_qualifiers : type -> tuple(type)
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auto ref_qualifiers = [](auto t) {
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return hana::make_tuple(
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hana::traits::add_lvalue_reference(t),
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hana::traits::add_rvalue_reference(t)
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);
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};
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auto possible_args = cv_qualifiers(hana::type_c<int>) | ref_qualifiers;
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BOOST_HANA_CONSTANT_CHECK(
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possible_args == hana::make_tuple(
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hana::type_c<int&>,
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hana::type_c<int&&>,
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hana::type_c<int const&>,
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hana::type_c<int const&&>,
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hana::type_c<int volatile&>,
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hana::type_c<int volatile&&>,
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hana::type_c<int const volatile&>,
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hana::type_c<int const volatile&&>
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)
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);
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struct some_function {
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template <typename T>
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void operator()(T&&) const { }
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};
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int main() {
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hana::for_each(possible_args, [](auto t) {
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using T = typename decltype(t)::type;
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static_assert(decltype(hana::is_valid(some_function{})(std::declval<T>())){},
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"some_function should be callable with any type of argument");
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});
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}
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