46 lines
1.3 KiB
C++
46 lines
1.3 KiB
C++
/*!
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@file
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Defines `boost::hana::make`.
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@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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*/
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#ifndef BOOST_HANA_CORE_MAKE_HPP
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#define BOOST_HANA_CORE_MAKE_HPP
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#include <boost/hana/fwd/core/make.hpp>
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#include <boost/hana/config.hpp>
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#include <boost/hana/core/default.hpp>
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#include <boost/hana/core/when.hpp>
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namespace boost { namespace hana {
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//! @cond
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template <typename Datatype, typename>
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struct make_impl : make_impl<Datatype, when<true>> { };
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//! @endcond
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template <typename Datatype, bool condition>
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struct make_impl<Datatype, when<condition>> : default_ {
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template <typename ...X>
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static constexpr auto make_helper(int, X&& ...x)
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-> decltype(Datatype(static_cast<X&&>(x)...))
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{ return Datatype(static_cast<X&&>(x)...); }
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template <typename ...X>
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static constexpr auto make_helper(long, X&& ...) {
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static_assert((sizeof...(X), false),
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"there exists no constructor for the given data type");
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}
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template <typename ...X>
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static constexpr decltype(auto) apply(X&& ...x)
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{ return make_helper(int{}, static_cast<X&&>(x)...); }
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};
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}} // end namespace boost::hana
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#endif // !BOOST_HANA_CORE_MAKE_HPP
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