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// Copyright (c) 2023 GeometryFactory Sarl (France).
// All rights reserved.
//
// This file is part of CGAL (www.cgal.org)
//
// $URL: https://github.com/CGAL/cgal/blob/v6.1.1/STL_Extension/include/CGAL/variant.h $
// $Id: include/CGAL/variant.h 08b27d3db14 $
// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
//
// Author(s) : Sébastien Loriot
//
#ifndef CGAL_VARIANT_H
#define CGAL_VARIANT_H
#include <variant>
namespace CGAL
{
template <class T, class Variant>
struct Is_in_variant;
template <class T, class V1, class ... Vn>
struct Is_in_variant<T, std::variant<V1,Vn...>>
{
inline static constexpr bool value =
std::is_same_v<T, V1> || Is_in_variant<T, std::variant<Vn...>>::value;
};
template <class T, class V>
struct Is_in_variant<T, std::variant<V>>
{
inline static constexpr bool value = std::is_same_v<T, V>;
};
/// equals true iif `T` is a possible type in `Variant` with `Variant` being a `std::variant`
template <class T, class Variant>
inline constexpr bool Is_in_variant_v = Is_in_variant<T, Variant>::value;
// --
template <class T, class Variant>
struct Add_to_variant;
template <class T, class ... Vn>
struct Add_to_variant<T, std::variant<Vn...>>
{
using type = std::variant<Vn..., T>;
};
/// a `std::variant` with `T` appended to the types of the `std::variant` `Variant`
template< class T, class Variant >
using Add_to_variant_t = typename Add_to_variant<T,Variant>::type;
namespace internal{
template <class Variant, class T1, class ... Tn>
struct Get_variant_impl
{
using type = typename Get_variant_impl<
std::conditional_t<Is_in_variant_v<T1, Variant>,
Variant,
Add_to_variant_t<T1,Variant>>,
Tn...>::type;
};
template <class Variant, class T1>
struct Get_variant_impl<Variant, T1>
{
using type = std::conditional_t<Is_in_variant_v<T1, Variant>,
Variant,
Add_to_variant_t<T1,Variant>>;
};
} // end of internal namespace
template <class T1, class ... Tn>
struct Variant_with_no_duplicate
{
using type = typename internal::Get_variant_impl<std::variant<T1>, Tn ...>::type;
};
/// a `std::variant` with types being all different
template< class ... Tn >
using Variant_with_no_duplicate_t = typename Variant_with_no_duplicate<Tn ... >::type;
} //end of CGAL namespace
#endif
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