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// Copyright Louis Dionne 2013-2017
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
#include <boost/hana/assert.hpp>
#include <boost/hana/chain.hpp>
#include <boost/hana/equal.hpp>
#include <boost/hana/for_each.hpp>
#include <boost/hana/traits.hpp>
#include <boost/hana/tuple.hpp>
#include <boost/hana/type.hpp>
#include <type_traits>
#include <utility>
namespace hana = boost::hana;
// Using the `tuple` Monad, we generate all the possible combinations of
// cv-qualifiers and reference qualifiers. Then, we use the `optional`
// Monad to make sure that our generic function can be called with
// arguments of any of those types.
// cv_qualifiers : type -> tuple(type)
auto cv_qualifiers = [](auto t) {
return hana::make_tuple(
t,
hana::traits::add_const(t),
hana::traits::add_volatile(t),
hana::traits::add_volatile(hana::traits::add_const(t))
);
};
// ref_qualifiers : type -> tuple(type)
auto ref_qualifiers = [](auto t) {
return hana::make_tuple(
hana::traits::add_lvalue_reference(t),
hana::traits::add_rvalue_reference(t)
);
};
auto possible_args = cv_qualifiers(hana::type_c<int>) | ref_qualifiers;
BOOST_HANA_CONSTANT_CHECK(
possible_args == hana::make_tuple(
hana::type_c<int&>,
hana::type_c<int&&>,
hana::type_c<int const&>,
hana::type_c<int const&&>,
hana::type_c<int volatile&>,
hana::type_c<int volatile&&>,
hana::type_c<int const volatile&>,
hana::type_c<int const volatile&&>
)
);
struct some_function {
template <typename T>
void operator()(T&&) const { }
};
int main() {
hana::for_each(possible_args, [](auto t) {
using T = typename decltype(t)::type;
static_assert(decltype(hana::is_valid(some_function{})(std::declval<T>())){},
"some_function should be callable with any type of argument");
});
}
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