referencehelper.hh

// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set et ts=4 sw=2 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_REFERENCE_HELPER_HH
#define DUNE_COMMON_REFERENCE_HELPER_HH
 
#include <type_traits>
#include <functional>
 
 
 
namespace Dune {
 
namespace Impl {
 
  template<class T>
  class IsReferenceWrapper : public std::false_type {};
 
  template<class T>
  class IsReferenceWrapper<std::reference_wrapper<T>> : public std::true_type {};
 
  template<class T>
  class IsReferenceWrapper<const std::reference_wrapper<T>> : public std::true_type {};
 
} // namespace Dune::Impl
 
 
template<class T>
constexpr bool IsReferenceWrapper_v = Impl::IsReferenceWrapper<T>::value;
 
 
template<class T>
constexpr T& resolveRef(T& gf) noexcept
{
  return gf;
}
 
 
// There's no overload for non std::reference_wrapper r-values,
// because this may lead to undefined behavior whenever the
// return value is stored.
// Notice that deleting the overload is not necessary, but
// helps to document that it is missing on purpose. It also
// leads to nicer error messages.
template<class T>
const auto& resolveRef(T&& gf) = delete;
 
 
template<class T>
constexpr T& resolveRef(std::reference_wrapper<T> gf) noexcept
{
  return gf.get();
}
 
 
 
template<class T>
using ResolveRef_t = std::remove_reference_t<decltype(Dune::resolveRef(std::declval<T&>()))>;
 
 
} // namespace Dune
 
 
 
#endif // DUNE_COMMON_REFERENCE_HELPER_HH