compositenode.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:
// SPDX-FileCopyrightInfo: Copyright © DUNE Project contributors, see file LICENSE.md in module root
// SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-GPL-2.0-only-with-PDELab-exception
 
#ifndef DUNE_TYPETREE_COMPOSITENODE_HH
#define DUNE_TYPETREE_COMPOSITENODE_HH
 
#include <tuple>
#include <memory>
#include <type_traits>
 
#include <dune/typetree/nodetags.hh>
#include <dune/typetree/childextraction.hh>
#include <dune/typetree/typetraits.hh>
 
namespace Dune {
  namespace TypeTree {
 
    template<typename... Children>
    class CompositeNode
    {
 
    public:
 
      typedef CompositeNodeTag NodeTag;
 
      typedef std::tuple<std::shared_ptr<Children>... > NodeStorage;
 
      typedef std::tuple<Children...> ChildTypes;
 
      static const bool isLeaf = false;
 
      static const bool isPower = false;
 
      static const bool isComposite = true;
 
      static constexpr auto degree ()
      {
        return std::integral_constant<std::size_t,sizeof...(Children)>{};
      }
 
      template<std::size_t k>
      struct Child {
 
        static_assert((k < degree()), "child index out of range");
 
        typedef typename std::tuple_element<k,ChildTypes>::type Type;
 
        typedef typename std::tuple_element<k,ChildTypes>::type type;
      };
 
 
 
      template<std::size_t k>
      typename Child<k>::Type& child (index_constant<k> = {})
      {
        return *std::get<k>(_children);
      }
 
 
      template<std::size_t k>
      const typename Child<k>::Type& child (index_constant<k> = {}) const
      {
        return *std::get<k>(_children);
      }
 
 
      template<std::size_t k>
      std::shared_ptr<typename Child<k>::Type> childStorage (index_constant<k> = {})
      {
        return std::get<k>(_children);
      }
 
 
      template<std::size_t k>
      std::shared_ptr<const typename Child<k>::Type> childStorage (index_constant<k> = {}) const
      {
        return std::get<k>(_children);
      }
 
      template<std::size_t k>
      void setChild (typename Child<k>::Type& child, index_constant<k> = {})
      {
        std::get<k>(_children) = stackobject_to_shared_ptr(child);
      }
 
      template<std::size_t k>
      void setChild (typename Child<k>::Type&& child, index_constant<k> = {})
      {
        std::get<k>(_children) = convert_arg(std::move(child));
      }
 
      template<std::size_t k>
      void setChild (std::shared_ptr<typename Child<k>::Type> child, index_constant<k> = {})
      {
        std::get<k>(_children) = std::move(child);
      }
 
      const NodeStorage& nodeStorage () const
      {
        return _children;
      }
 
 
 
      // The following two methods require a little bit of SFINAE trickery to work correctly:
      // We have to make sure that they don't shadow the methods for direct child access because
      // those get called by the generic child() machinery. If that machinery picks up the methods
      // defined below, we have an infinite recursion.
      // So the methods make sure that either
      //
      // * there are more than one argument. In that case, we got multiple indices and can forward
      //   to the general machine.
      //
      // * the first argument is not a valid flat index, i.e. either a std::size_t or an index_constant.
      //   The argument thus has to be some kind of TreePath instance that we can also pass to the
      //   generic machine.
      //
      // The above SFINAE logic works, but there is still a problem with the return type deduction.
      // We have to do a lazy lookup of the return type after SFINAE has succeeded, otherwise the return
      // type deduction will trigger the infinite recursion.
 
 
#ifdef DOXYGEN
      template<typename... Indices>
      ImplementationDefined& child (Indices... indices)
#else
      template<typename I0, typename... I,
        std::enable_if_t<(sizeof...(I) > 0) || IsTreePath<I0>::value, int > = 0>
      decltype(auto) child (I0 i0, I... i)
#endif
      {
        static_assert(sizeof...(I) > 0 || impl::_non_empty_tree_path(I0{}),
          "You cannot use the member function child() with an empty TreePath, use the freestanding version child(node,treePath) instead."
          );
        return Dune::TypeTree::child(*this,i0,i...);
      }
 
 
#ifdef DOXYGEN
      template<typename... Indices>
      const ImplementationDefined& child (Indices... indices)
#else
      template<typename I0, typename... I,
        std::enable_if_t<(sizeof...(I) > 0) || IsTreePath<I0>::value, int > = 0>
      decltype(auto) child (I0 i0, I... i) const
#endif
      {
        static_assert(sizeof...(I) > 0 || impl::_non_empty_tree_path(I0{}),
          "You cannot use the member function child() with an empty TreePath, use the freestanding version child(node,treePath) instead."
          );
        return Dune::TypeTree::child(*this,i0,i...);
      }
 
 
    protected:
 
 
 
      CompositeNode ()
      {}
 
      template<typename... Args, typename = typename std::enable_if<(sizeof...(Args) == degree())>::type>
      CompositeNode (Args&&... args)
        : _children(convert_arg(std::forward<Args>(args))...)
      {}
 
      CompositeNode (std::shared_ptr<Children>... children)
        : _children(std::move(children)...)
      {}
 
      CompositeNode (const NodeStorage& children)
        : _children(children)
      {}
 
 
    private:
      NodeStorage _children;
    };
 
 
  } // namespace TypeTree
} //namespace Dune
 
#endif // DUNE_TYPETREE_COMPOSITENODE_HH