37 lines
1.9 KiB
C++
37 lines
1.9 KiB
C++
// Copyright (c) 2017 Inria (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: https://github.com/CGAL/cgal/blob/v5.1/STL_Extension/include/CGAL/Has_member.h $
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// $Id: Has_member.h 52164b1 2019-10-19T15:34:59+02:00 Sébastien Loriot
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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) : Clement Jamin
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#ifndef CGAL_HAS_MEMBER_H
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#define CGAL_HAS_MEMBER_H
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// Macro used to check if a type T has a member named `X`
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// It generates a class has_X<T> where has_X<T>::value is a boolean
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// See example in Concurrent_compact_container.h
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#define CGAL_GENERATE_MEMBER_DETECTOR(X) \
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template<typename T> class has_##X { \
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struct Fallback { int X; }; \
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struct Derived : T, Fallback { }; \
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\
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template<typename U, U> struct Check; \
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\
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typedef char ArrayOfOne[1]; \
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typedef char ArrayOfTwo[2]; \
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\
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template<typename U> static ArrayOfOne & func( \
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Check<int Fallback::*, &U::X> *); \
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template<typename U> static ArrayOfTwo & func(...); \
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public: \
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typedef has_##X type; \
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enum { value = sizeof(func<Derived>(0)) == 2 }; \
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} // semicolon is after the macro call
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#endif // CGAL_HAS_MEMBER_H
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