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// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set et ts=4 sw=2 sts=2:
#ifndef DUNE_FUNCTIONS_FUNCTIONSPACEBASES_FLATMULTIINDEX_HH
#define DUNE_FUNCTIONS_FUNCTIONSPACEBASES_FLATMULTIINDEX_HH
#include <array>
#include <dune/common/hash.hh>
namespace Dune {
namespace Functions {
/**
* \brief A multi-index class with only one level
*
* \ingroup FunctionSpaceBasesUtilities
*
* This class provides a multi-index interface in the sense
* that it has operator[] access to individual interfaces.
* However, since it only supports flat indices of exactly
* one level, it also has a cast of the multi-index to
* this index.
* This is obtianed by deriving from std::array<size_type,1>
* and adding this cast.
* Hence multi-indices of type FlatMultiIndex can be used like
* classic indices.
*/
template<class size_type>
class FlatMultiIndex :
public std::array<size_type,1>
{
public:
constexpr FlatMultiIndex() = default;
/**
* \brief Construct from initializer_list
*
* This is needed because std::array does not have
* a constructor from initializer list. Instead
* the list initialization of an std::array is
* an aggregate initialization and hence not
* visible in the derived class.
*/
FlatMultiIndex(std::initializer_list<size_type> const &l) :
std::array<size_type,1>{{*l.begin()}}
{}
/**
* \brief Const cast of multi-index to first entry
*
* \returns The first (and only) index of this multi-index
*/
operator const size_type& () const
{
return this->operator[](0);
}
/**
* \brief Non-const cast of multi-index to first entry
*
* \returns The first (and only) index of this multi-index
*/
operator size_type& ()
{
return this->operator[](0);
}
/**
* \brief Compute hash value for FlatMultiIndex
*
* \ingroup FunctionSpaceBasesUtilities
*/
inline friend std::size_t hash_value(const FlatMultiIndex& arg) noexcept
{
return std::hash<size_type>()(arg);
}
};
} // end namespace Functions
} // end namespace Dune
DUNE_DEFINE_HASH(DUNE_HASH_TEMPLATE_ARGS(typename size_type),DUNE_HASH_TYPE(Dune::Functions::FlatMultiIndex<size_type>))
#endif // DUNE_FUNCTIONS_FUNCTIONSPACEBASES_FLATMULTIINDEX_HH
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