75 lines
2.4 KiB
C++
75 lines
2.4 KiB
C++
// Copyright Louis Dionne 2013-2017
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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/bool.hpp>
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#include <boost/hana/fwd/hash.hpp>
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#include <boost/hana/map.hpp>
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#include <boost/hana/pair.hpp>
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#include <boost/hana/type.hpp>
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#include <type_traits>
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namespace hana = boost::hana;
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struct NoDefault {
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NoDefault() = delete;
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NoDefault(NoDefault const&) = default;
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constexpr explicit NoDefault(int) { }
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};
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auto operator==(NoDefault const&, NoDefault const&) { return hana::true_c; }
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auto operator!=(NoDefault const&, NoDefault const&) { return hana::false_c; }
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// Note: It is also useful to check with a non-empty class, because that
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// triggers different instantiations due to EBO.
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struct NoDefault_nonempty {
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NoDefault_nonempty() = delete;
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NoDefault_nonempty(NoDefault_nonempty const&) = default;
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constexpr explicit NoDefault_nonempty(int k) : i(k) { }
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int i;
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};
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auto operator==(NoDefault_nonempty const&, NoDefault_nonempty const&) { return hana::true_c; }
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auto operator!=(NoDefault_nonempty const&, NoDefault_nonempty const&) { return hana::false_c; }
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struct Default {
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Default() = default;
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Default(Default const&) = default;
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constexpr explicit Default(int) { }
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};
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auto operator==(Default const&, Default const&) { return hana::true_c; }
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auto operator!=(Default const&, Default const&) { return hana::false_c; }
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namespace boost { namespace hana {
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template <>
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struct hash_impl<NoDefault> {
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static constexpr auto apply(NoDefault const&)
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{ return hana::type_c<NoDefault>; };
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};
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template <>
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struct hash_impl<NoDefault_nonempty> {
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static constexpr auto apply(NoDefault_nonempty const&)
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{ return hana::type_c<NoDefault_nonempty>; };
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};
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template <>
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struct hash_impl<Default> {
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static constexpr auto apply(Default const&)
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{ return hana::type_c<Default>; };
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};
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}}
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int main() {
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auto map1 = hana::make_map(hana::make_pair(Default(1), Default(1)));
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static_assert(std::is_default_constructible<decltype(map1)>::value, "");
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auto map2 = hana::make_map(hana::make_pair(NoDefault(1), NoDefault(1)));
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static_assert(!std::is_default_constructible<decltype(map2)>::value, "");
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auto map3 = hana::make_map(hana::make_pair(NoDefault_nonempty(1), NoDefault_nonempty(1)));
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static_assert(!std::is_default_constructible<decltype(map3)>::value, "");
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}
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