70 lines
2.1 KiB
C
70 lines
2.1 KiB
C
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// Copyright (c) 2001
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// Utrecht University (The Netherlands),
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// ETH Zurich (Switzerland),
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// INRIA Sophia-Antipolis (France),
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// Max-Planck-Institute Saarbruecken (Germany),
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// and Tel-Aviv University (Israel). All rights reserved.
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//
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// This file is part of CGAL (www.cgal.org); you can redistribute it and/or
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// modify it under the terms of the GNU Lesser General Public License as
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// published by the Free Software Foundation; either version 3 of the License,
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// or (at your option) any later version.
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//
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// Licensees holding a valid commercial license may use this file in
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// accordance with the commercial license agreement provided with the software.
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//
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// This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
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// WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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//
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// $URL$
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// $Id$
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// SPDX-License-Identifier: LGPL-3.0+
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//
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//
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// Author(s) : Sylvain Pion
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#ifndef CGAL_KERNEL_TRAITS_H
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#define CGAL_KERNEL_TRAITS_H
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#include <CGAL/Kernel_traits_fwd.h>
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#include <boost/mpl/has_xxx.hpp>
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#include <boost/mpl/if.hpp>
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namespace CGAL {
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namespace internal_kernel_traits{
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BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(Has_nested_R,R,false)
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/// In case no specialization of CGAL::Kernel_traits is provided and the type used
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/// is not coming from a CGAL Kernel, we provide a dummy Kernel just to break later
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/// and only when it is used. This was introduced to avoid issues with a free function
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/// return a nested type of the kernel through Kernel_traits. Even if the function
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/// was not the one to consider, its return type should be instanciable.
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template <class T>
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struct Dummy_kernel
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{
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struct FT{};
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};
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template <class T, bool is_cgal_kernel = Has_nested_R<T>::value >
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struct Kernel_traits{
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typedef typename T::R type;
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};
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template <class T>
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struct Kernel_traits<T, false>{
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typedef Dummy_kernel<T> type;
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};
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} // end of namespace internal_kernel_traits
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template <class T>
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struct Kernel_traits
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{
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typedef typename internal_kernel_traits::Kernel_traits<T>::type Kernel;
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typedef Kernel type;
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};
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} // end namespace CGAL
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#endif // CGAL_KERNEL_TRAITS_H
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