functional.hh

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// -*- tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set ts=8 sw=2 et sts=2:
// SPDX-FileCopyrightInfo: Copyright © DUNE Project contributors, see file LICENSE.md in module root
// SPDX-License-Identifier: LicenseRef-GPL-2.0-only-with-DUNE-exception
#ifndef DUNE_COMMON_STD_FUNCTIONAL_HH
#define DUNE_COMMON_STD_FUNCTIONAL_HH

#include <functional>

#include <dune-common-config.hh> // DUNE_HAVE_CXX_STD_IDENTITY

namespace Dune
{

  namespace Std
  {

#if DUNE_HAVE_CXX_STD_IDENTITY
    using std::identity;
#else //DUNE_HAVE_CXX_STD_IDENTITY
    struct identity {
      template<class T>
      constexpr T&& operator()(T&& t ) const noexcept {return std::forward<T>(t);}
    };
#endif
  } // namespace Std

} // namespace Dune

#endif // #ifndef DUNE_COMMON_STD_FUNCTIONAL_HH