optional.h

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// ---------------------------------------------------------------------
//
// Copyright (C) 2019 by the deal.II authors
//
// This file is part of the deal.II library.
//
// The deal.II library is free software; you can use it, redistribute
// it, and/or modify it under the terms of the GNU Lesser General
// Public License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
// The full text of the license can be found in the file LICENSE.md at
// the top level directory of deal.II.
//
// ---------------------------------------------------------------------
#ifndef dealii_cxx17_optional_h
#define dealii_cxx17_optional_h
 
#include <deal.II/base/config.h>
 
#ifdef __cpp_lib_optional
#  include <optional>
#else
#  include <boost/optional.hpp>
#endif
 
DEAL_II_NAMESPACE_OPEN
namespace std_cxx17
{
#ifdef __cpp_lib_optional
  using std::optional;
#else
  using boost::optional;
#endif
} // namespace std_cxx17
DEAL_II_NAMESPACE_CLOSE
 
#endif // dealii_cxx17_optional_h