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// Copyright (c) 2001
// Utrecht University (The Netherlands),
// ETH Zurich (Switzerland),
// INRIA Sophia-Antipolis (France),
// Max-Planck-Institute Saarbruecken (Germany),
// and Tel-Aviv University (Israel). All rights reserved.
//
// This file is part of CGAL (www.cgal.org)
//
// $URL: https://github.com/CGAL/cgal/blob/v6.1.1/Kernel_23/include/CGAL/Kernel_traits.h $
// $Id: include/CGAL/Kernel_traits.h 08b27d3db14 $
// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-Commercial
//
//
// Author(s) : Sylvain Pion
#ifndef CGAL_KERNEL_TRAITS_H
#define CGAL_KERNEL_TRAITS_H
#include <CGAL/Kernel_traits_fwd.h>
#include <boost/mpl/has_xxx.hpp>
namespace CGAL {
namespace internal_kernel_traits{
BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(Has_nested_R,R,false)
/// In case no specialization of CGAL::Kernel_traits is provided and the type used
/// is not coming from a CGAL Kernel, we provide a dummy Kernel just to break later
/// and only when it is used. This was introduced to avoid issues with a free function
/// return a nested type of the kernel through Kernel_traits. Even if the function
/// was not the one to consider, its return type should be instanciable.
template <class T>
struct Dummy_kernel
{
struct FT{};
};
template <class T, bool is_cgal_kernel = Has_nested_R<T>::value >
struct Kernel_traits{
typedef typename T::R type;
};
template <class T>
struct Kernel_traits<T, false>{
typedef Dummy_kernel<T> type;
};
} // end of namespace internal_kernel_traits
template <class T>
struct Kernel_traits
{
typedef typename internal_kernel_traits::Kernel_traits<T>::type Kernel;
typedef Kernel type;
};
} // end namespace CGAL
#endif // CGAL_KERNEL_TRAITS_H
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