mirror of https://github.com/CGAL/cgal
88 lines
2.2 KiB
C++
88 lines
2.2 KiB
C++
// Copyright (c) 2023 GeometryFactory Sarl (France).
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// All rights reserved.
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//
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// This file is part of CGAL (www.cgal.org)
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//
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// $URL$
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// $Id$
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// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
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//
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// Author(s) : Sébastien Loriot
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//
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#ifndef CGAL_VARIANT_H
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#define CGAL_VARIANT_H
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#include <variant>
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namespace CGAL
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{
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template <class T, class Variant>
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struct Is_in_variant;
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template <class T, class V1, class ... Vn>
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struct Is_in_variant<T, std::variant<V1,Vn...>>
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{
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inline static constexpr bool value =
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std::is_same_v<T, V1> || Is_in_variant<T, std::variant<Vn...>>::value;
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};
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template <class T, class V>
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struct Is_in_variant<T, std::variant<V>>
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{
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inline static constexpr bool value = std::is_same_v<T, V>;
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};
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/// equals true iif `T` is a possible type in `Variant` with `Variant` being a `std::variant`
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template <class T, class Variant>
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inline constexpr bool Is_in_variant_v = Is_in_variant<T, Variant>::value;
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// --
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template <class T, class Variant>
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struct Add_to_variant;
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template <class T, class ... Vn>
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struct Add_to_variant<T, std::variant<Vn...>>
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{
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using type = std::variant<Vn..., T>;
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};
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/// a `std::variant` with `T` appended to the types of the `std::variant` `Variant`
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template< class T, class Variant >
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using Add_to_variant_t = typename Add_to_variant<T,Variant>::type;
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namespace internal{
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template <class Variant, class T1, class ... Tn>
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struct Get_variant_impl
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{
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using type = typename Get_variant_impl<
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std::conditional_t<Is_in_variant_v<T1, Variant>,
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Variant,
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Add_to_variant_t<T1,Variant>>,
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Tn...>::type;
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};
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template <class Variant, class T1>
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struct Get_variant_impl<Variant, T1>
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{
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using type = std::conditional_t<Is_in_variant_v<T1, Variant>,
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Variant,
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Add_to_variant_t<T1,Variant>>;
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};
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} // end of internal namespace
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template <class T1, class ... Tn>
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struct Variant_with_no_duplicate
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{
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using type = typename internal::Get_variant_impl<std::variant<T1>, Tn ...>::type;
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};
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/// a `std::variant` with types being all different
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template< class ... Tn >
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using Variant_with_no_duplicate_t = typename Variant_with_no_duplicate<Tn ... >::type;
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} //end of CGAL namespace
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#endif
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