referenceelements.hh

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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_GEOMETRY_REFERENCEELEMENTS_HH
#define DUNE_GEOMETRY_REFERENCEELEMENTS_HH
 
#include <cassert>
 
#include <algorithm>
#include <limits>
#include <tuple>
#include <utility>
#include <vector>
#include <array>
 
#include <dune/common/typetraits.hh>
#include <dune/common/std/type_traits.hh>
#include <dune/common/visibility.hh>
 
#include <dune/geometry/dimension.hh>
#include <dune/geometry/type.hh>
#include <dune/geometry/referenceelement.hh>
#include <dune/geometry/referenceelementimplementation.hh>
 
namespace Dune
{
 
  namespace Geo
  {
 
#ifndef DOXYGEN
 
 
    template<typename ctype, int dim>
    class DeprecatedReferenceElement
      : public ReferenceElement<ReferenceElementImplementation<ctype,dim>>
    {
 
    protected:
 
      DeprecatedReferenceElement() = default;
 
    public:
 
      DeprecatedReferenceElement(const DeprecatedReferenceElement&) = delete;
      DeprecatedReferenceElement& operator=(const DeprecatedReferenceElement&) = delete;
 
      DeprecatedReferenceElement(const ReferenceElementImplementation<ctype,dim>& impl)
        : ReferenceElement<ReferenceElementImplementation<ctype,dim>>(impl)
      {}
 
    };
 
 
    template<typename ctype, int dim>
    class ConstructibleDeprecatedReferenceElement
      : public DeprecatedReferenceElement<ctype,dim>
    {
    public:
      ConstructibleDeprecatedReferenceElement() = default;
    };
 
 
    namespace Impl
    {
 
      // ReferenceElementContainer
      // -------------------------
 
      template< class ctype, int dim >
      class ReferenceElementContainer
      {
        static const unsigned int numTopologies = dim >= 0 ? (1u << dim) : 0;
 
        using Implementation   = ReferenceElementImplementation< ctype, dim >;
        using ConstructibleDeprecatedReferenceElement = Dune::Geo::ConstructibleDeprecatedReferenceElement<ctype,dim>;
 
      public:
 
        using DeprecatedReferenceElement = Dune::Geo::DeprecatedReferenceElement<ctype,dim>;
 
        using ReferenceElement = Dune::Geo::ReferenceElement< Implementation >;
        using value_type       = ReferenceElement;
        using const_iterator   = const value_type*;
 
        ReferenceElementContainer ()
        {
          for( unsigned int topologyId = 0; topologyId < numTopologies; ++topologyId )
            {
              implementations_[ topologyId ].initialize( topologyId );
              reference_elements_[ topologyId ].setImplementation( implementations_[ topologyId ] );
            }
        }
 
        const ReferenceElement& operator() ( const GeometryType &type ) const
        {
          assert( type.dim() == dim );
          return reference_elements_[ type.id() ];
        }
 
        const ReferenceElement& simplex () const
        {
          return reference_elements_[ Dune::GeometryTypes::simplex(dim).id() ];
        }
 
        const ReferenceElement& cube () const
        {
          return reference_elements_[ Dune::GeometryTypes::cube(dim).id() ];
        }
 
        const ReferenceElement& pyramid () const
        {
          return reference_elements_[ Dune::GeometryTypes::pyramid.id() ];
        }
 
        const ReferenceElement& prism () const
        {
          return reference_elements_[ Dune::GeometryTypes::prism.id() ];
        }
 
        const_iterator begin () const
        {
          return reference_elements_.data();
        }
 
        const_iterator end () const
        {
          return reference_elements_.data() + numTopologies;
        }
 
        // here, we make sure to actually return a const reference to something
        // that is guaranteed not to become invalid, as otherwise, we might run
        // straight into debugging hell when a user binds the return value to a
        // const ref and the temporary goes out of scope.
        const DeprecatedReferenceElement& deprecated(const ReferenceElement& v) const
        {
          return reference_elements_[v.impl().type(0,0).id()];
        }
 
      private:
 
        std::array<Implementation,numTopologies> implementations_;
        std::array<ConstructibleDeprecatedReferenceElement,numTopologies> reference_elements_;
 
      };
 
 
    } // namespace Impl
 
 
#endif // DOXYGEN
 
 
    // ReferenceElements
    // ------------------------
 
    template< class ctype_, int dim >
    struct ReferenceElements
    {
 
      using ctype = ctype_;
 
      using CoordinateField = ctype;
 
      static constexpr int dimension = dim;
 
    private:
 
      using Container = Impl::ReferenceElementContainer< ctype, dim >;
 
    public:
 
      using ReferenceElement = typename Container::ReferenceElement;
 
      using Iterator         = typename Container::const_iterator;
 
      using iterator         = Iterator;
 
      static const ReferenceElement&
      general ( const GeometryType& type )
      {
        return container() ( type );
      }
 
      static const ReferenceElement& simplex ()
      {
        return container().simplex();
      }
 
      static const ReferenceElement& cube ()
      {
        return container().cube();
      }
 
      static Iterator begin ()
      {
        return container().begin();
      }
 
      static Iterator end ()
      {
        return container().end();
      }
 
#ifndef DOXYGEN
      static const typename Container::DeprecatedReferenceElement&
      deprecated(const ReferenceElement& v)
      {
        return container().deprecated(v);
      }
#endif // DOXYGEN
 
    private:
 
      DUNE_EXPORT static const Container& container ()
      {
        static Container container;
        return container;
      }
    };
 
  } // namespace Geo
 
  using Geo::ReferenceElements;
 
 
#ifdef DOXYGEN
 
 
  template<typename... T>
  unspecified-value-type referenceElement(T&&... t);
 
#endif
 
 
 
  template<typename T, int dim>
  auto referenceElement(const Dune::GeometryType& gt, Dune::Dim<dim> = {})
  {
    return ReferenceElements<T,dim>::general(gt);
  }
 
 
 
  template<typename T, int dim, std::enable_if_t<IsNumber<std::decay_t<T>>::value, int> = 0>
  auto referenceElement(const T&, const Dune::GeometryType& gt, Dune::Dim<dim>)
  {
    return ReferenceElements<T,dim>::general(gt);
  }
 
 
#ifndef DOXYGEN
 
  // helpers for the ReferenceElement<> meta function
 
  namespace Impl {
 
    // Evaluates to the correct reference element iff <T...> matches the pattern <number_type,Dim<int>>
    // otherwise, it's ill-formed. Should be used with detected_or and friends.
 
    template<typename... T>
    struct DefaultReferenceElementExtractor;
 
    template<typename T, typename std::enable_if<IsNumber<T>::value,int>::type dim>
    struct DefaultReferenceElementExtractor<T,Dim<dim>>
    {
      using type = typename Dune::Geo::ReferenceElements<T,dim>::ReferenceElement;
    };
 
    template<typename... T>
    using DefaultReferenceElement = typename DefaultReferenceElementExtractor<T...>::type;
 
  }
 
  // looks up the type of a reference element by trying to instantiate the correct overload
  // of referenceElement() for the given arguments. This will fail if there is no valid
  // overload and should be used with detected_or or some other utility that places the
  // instantation in SFINAE context.
  //
  // this is placed directly in namespace Dune to avoid any weird surprises
 
  template<typename... T>
  using LookupReferenceElement = decltype(referenceElement(std::declval<T>()...));
 
#endif // DOXYGEN
 
  namespace Transitional {
 
#ifndef DOXYGEN
 
    // this abomination checks whether the template signature matches the special case
    // ReferenceElement<number_type,Dune::Dim<int>> and otherwise defers the type lookup
    // to a decltype on a call to referenceElement(std::declval<T>())
 
    template<typename... T>
    using ReferenceElement = Std::detected_or_t<
      Std::detected_t<LookupReferenceElement,T...>,
      Impl::DefaultReferenceElement,
      T...
      >;
 
#else // DOXYGEN
 
 
    template<typename... T>
    using ReferenceElement = unspecified-type;
 
#endif //DOXYGEN
 
  }
 
#ifndef DOXYGEN
 
  namespace Impl {
 
    // helpers for triggering a deprecation warning for occurences of the old
    // ReferenceElement syntax (Dune::ReferenceElement<T,int>)
 
    // this looks a little weird, encoding the type in the return type of a nested function,
    // but it was the only reliable way to trigger the warning iff the compiler encounters
    // an invalid use. Other solutions either miss some (or all) uses or trigger false alarms.
 
    template<typename T>
    struct ValidReferenceElementTypeSignature
    {
      Transitional::ReferenceElement<T> check();
    };
 
    template<typename T>
    struct DeprecatedReferenceElementTypeSignature
    {
      [[deprecated("Dune::ReferenceElement<T,int> is deprecated, please use Dune::ReferenceElement<Geometry> (if you have a geometry), Dune::ReferenceElements<T,int>::ReferenceElement or Dune::Transitional::ReferenceElement<T,Dune::Dim<int>> instead. After Dune 2.6, you will be able to use Dune::ReferenceElement<T,Dune::Dim<int>>.")]] T check();
    };
 
  } // namespace Impl
 
  // This just makes sure the user doesn't use invalid syntax (by checking against the -1 default for
  // the dimension, and then either hands back the old-style type along with a deprecation warning or
  // forwards to the transitional version
  template<typename T, int dim = -1>
  using ReferenceElement = decltype(
    std::declval<
      typename std::conditional<
        dim == -1,
        Impl::ValidReferenceElementTypeSignature<T>,
        Impl::DeprecatedReferenceElementTypeSignature<Geo::DeprecatedReferenceElement<T,dim>>
        >::type
      >().check());
 
#else // DOXYGEN
 
 
  template<typename T, int dim>
  using ReferenceElement = unspecified-type;
 
#endif // DOXYGEN
 
 
 
} // namespace Dune
 
#endif // #ifndef DUNE_GEOMETRY_REFERENCEELEMENTS_HH