Sébastien Loriot
3346aed52b
in a free function that has such a return type, if there are several overloads the return type of each should be instanciable. This fix will make incorrect usages break later while enabling the use in free function.
68 lines
2.0 KiB
C++
68 lines
2.0 KiB
C++
// 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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//
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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 <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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