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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
{
/**
* @brief A function object type whose operator() returns its argument unchanged
* @note Equivalent to: `return std::forward(t);`
* @warning When passing `r-values`, the result must be, at most, used for direct
* consumption in an outer function call
*/
#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
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