filters.hh

// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set et ts=4 sw=2 sts=2:
 
#ifndef DUNE_TYPETREE_FILTERS_HH
#define DUNE_TYPETREE_FILTERS_HH
 
#include <tuple>
 
#include <dune/common/typetraits.hh>
 
namespace Dune {
  namespace TypeTree {
 
    template<std::size_t new_k, std::size_t old_k>
    struct FilterEntry
    {
 
#ifndef DOXYGEN
 
      // The precise contents of this class is an implementation detail.
 
      static const std::size_t filtered_index = new_k;
      static const std::size_t original_index = old_k;
 
#endif // DOXYGEN
 
    };
 
    template<typename... FilterEntries>
    struct FilterResult
    {
 
      static const std::size_t size = sizeof...(FilterEntries);
 
      typedef std::tuple<FilterEntries...> IndexMap;
 
      template<typename Node>
      struct apply
      {
        typedef std::tuple<typename Node::template Child<FilterEntries::original_index>...> Children;
        typedef std::tuple<typename Node::template Child<FilterEntries::original_index>::Type...> ChildTypes;
        typedef std::tuple<typename Node::template Child<FilterEntries::original_index>::Storage...> NodeStorage;
      };
 
    };
 
    struct SimpleFilterTag {};
 
    struct AdvancedFilterTag {};
 
 
    struct AdvancedFilter
    {
 
      typedef AdvancedFilterTag FilterTag;
 
#ifdef DOXYGEN
 
      template<typename Node, typename... Children>
      struct apply
      {
 
        typedef implementation-defined type;
      };
 
#endif // DOXYGEN
 
    };
 
 
    struct SimpleFilter
    {
 
      typedef SimpleFilterTag FilterTag;
 
 
      template<typename Node>
      struct validate
      {
        static const bool value = true;
      };
 
 
      template<typename Child, std::size_t new_index, std::size_t old_index>
      struct apply
      {
        static const bool value = true;
      };
 
    };
 
    namespace {
 
      // ********************************************************************************
      // IndexFilter helpers
      // ********************************************************************************
 
      template<typename Node, std::size_t new_index, std::size_t... indices>
      struct index_filter_helper
      {
        template<typename... FilterEntries>
        struct apply
        {
          typedef FilterResult<FilterEntries...> type;
        };
      };
 
      template<typename Node, std::size_t new_index, std::size_t old_index, std::size_t... indices>
      struct index_filter_helper<Node,new_index,old_index,indices...>
      {
        template<typename... FilterEntries>
        struct apply
          : public index_filter_helper<Node,new_index+1,indices...>::template apply<FilterEntries...,
                                                                                    FilterEntry<new_index,
                                                                                                old_index>
                                                                                    >
        {};
      };
 
    } // anonymous namespace
 
 
    template<std::size_t... indices>
    struct IndexFilter
      : public AdvancedFilter
    {
 
#ifndef DOXYGEN
 
      template<typename Node, typename... Children>
      struct apply
      {
        typedef typename index_filter_helper<Node,0,indices...>::template apply<>::type type;
      };
 
#endif // DOXYGEN
 
    };
 
 
    // ********************************************************************************
    // filter: Wrapper class for turning a simple filter into an advanced filter
    //         usable by FilteredCompositeNode
    // ********************************************************************************
 
    namespace {
 
      template<typename Filter, std::size_t new_k, std::size_t old_k, typename... tail>
      struct filter_helper
      {
        template<typename... FilterDescriptors>
        struct apply
        {
          typedef FilterResult<FilterDescriptors...> type;
        };
      };
 
      template<typename Filter, std::size_t new_k, std::size_t old_k, typename child, typename... tail>
      struct filter_helper<Filter,new_k,old_k,child,tail...>
      {
 
        template<typename... FilterDescriptors>
        struct apply
          : public std::conditional<Filter::template apply<child,new_k,old_k>::value,
                                    typename filter_helper<Filter,new_k+1,old_k+1,tail...>::template apply<FilterDescriptors...,FilterEntry<new_k,old_k> >,
                                    typename filter_helper<Filter,new_k,old_k+1,tail...>::template apply<FilterDescriptors...>
                                   >::type
        {};
 
      };
 
    } // anonymous namespace
 
    template<typename Filter>
    struct filter
    {
 
      template<typename Node, typename... Children>
      struct apply
      {
 
        static_assert((Filter::template validate<Node>::value),"Invalid simple filter");
 
        typedef typename filter_helper<Filter,0,0,Children...>::template apply<>::type type;
 
      };
 
    };
 
 
  } // namespace TypeTree
} //namespace Dune
 
#endif // DUNE_TYPETREE_FILTERS_HH