treepath.hh

// -*- tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set et ts=8 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_TREEPATH_HH
#define DUNE_TYPETREE_TREEPATH_HH
 
#include <cstddef>
#include <cassert>
#include <iostream>
#include <type_traits>
 
#include <dune/common/documentation.hh>
#include <dune/common/version.hh>
#include <dune/common/typetraits.hh>
#include <dune/common/indices.hh>
#include <dune/common/hybridutilities.hh>
#include <dune/common/typelist.hh>
 
namespace Dune {
  namespace TypeTree {
 
    // The Impl namespace collects some free standing functions helper functions
    namespace Impl {
      template<typename T>
      struct check_size_t_impl
      {
        static constexpr auto check() {
          return std::is_same_v<T, std::size_t>;
        }
      };
 
      template<class T, T v>
      struct check_size_t_impl<std::integral_constant<T,v>>
      {
        static constexpr auto check() {
          return std::is_same_v<T, std::size_t>;
        }
      };
 
      template<typename T>
      constexpr auto check_size_t() {
        return check_size_t_impl<T>::check();
      }
 
      template<typename T>
      constexpr auto cast_size_t(const T & v) {
        // check that T is an integral type that can be cast to std::size_t
        static_assert(
          std::is_convertible_v<T,std::size_t> &&
          std::is_integral_v<T>,
          "HybridTreePath indices must be convertible to std::size_t or std::integral_constant<std::size_t,v>");
        // positivity can only be checked at run-time
        assert(v >= 0 &&
          "HybridTreePath indices must be convertible to std::size_t or std::integral_constant<std::size_t,v>");
        return std::size_t(v);
      }
 
      template<class T, T v>
      constexpr auto cast_size_t(std::integral_constant<T,v>) {
        // check that T is an intergal type that can be cast to std::size_t
        // and that v is positive
        static_assert(
          std::is_convertible_v<T,std::size_t> &&
          std::is_integral_v<T> &&
          v >= 0,
          "HybridTreePath indices must be convertible to std::size_t or std::integral_constant<std::size_t,v>");
        return std::integral_constant<std::size_t,v>();
      }
 
      // these are helper functions that help triggering a deprecation warning
      template<typename T>
      [[deprecated("HybridTreePath index storage should be std::size_t or std::integral_constant<std::size_t,v>!\n"
            "Using anything else is deprecated and will not possible after the 2.10 release.\n"
            "It is adviced not to specify the template parameters expicitly,\n"
            "but to use the helper functions `hybridTreePath` or `treePath`."
            "These take care of converting indices to the appropriate storage.")]]
      constexpr bool check_storage_type(MetaType<T>) {
        return false;
      }
 
      // specialization of valid index type
      template<std::size_t v>
      constexpr bool check_storage_type(MetaType<std::integral_constant<std::size_t,v>>) {
        return true;
      }
 
      // specialization of valid index type
      constexpr bool check_storage_type(MetaType<std::size_t>) {
        return true;
      }
    }
 
    template<typename... T>
    class HybridTreePath;
 
 
    namespace TreePathType {
      enum Type { fullyStatic, dynamic };
    }
 
    template<typename>
    struct TreePathSize;
 
    template<typename,std::size_t>
    struct TreePathPushBack;
 
    template<typename,std::size_t>
    struct TreePathPushFront;
 
    template<typename>
    struct TreePathBack;
 
    template<typename>
    struct TreePathFront;
 
    template<typename, std::size_t...>
    struct TreePathPopBack;
 
    template<typename>
    struct TreePathPopFront;
 
    template<typename, typename>
    struct TreePathConcat;
 
    template<std::size_t... i>
    void print_tree_path(std::ostream& os)
    {}
 
    template<std::size_t k, std::size_t... i>
    void print_tree_path(std::ostream& os)
    {
      os << k << " ";
      print_tree_path<i...>(os);
    }
 
 
    template<typename... T>
    class HybridTreePath
    {
 
      // enable check for dune-typetree 2.10 and above
#if DUNE_VERSION_GTE(TYPETREE,2,10)
      // make sure that all indices use std::size_t as the underlying number type
      static_assert((... && Impl::check_size_t<T>()),
        "HybridTreePath index storage must be std::size_t or std::integral_constant<std::size_t,v>");
#endif
 
    public:
 
      using index_sequence = std::index_sequence_for<T...>;
 
      constexpr HybridTreePath()
      {
        [[maybe_unused]] constexpr bool check =
          (... && Impl::check_storage_type(MetaType<T>()) );
      }
 
      constexpr HybridTreePath(const HybridTreePath& tp) = default;
      constexpr HybridTreePath(HybridTreePath&& tp) = default;
 
      constexpr HybridTreePath& operator=(const HybridTreePath& tp) = default;
      constexpr HybridTreePath& operator=(HybridTreePath&& tp) = default;
 
      explicit constexpr HybridTreePath(std::tuple<T...> t)
        : _data(t)
      {
        [[maybe_unused]] constexpr bool check =
          (... && Impl::check_storage_type(MetaType<T>()) );
      }
 
      template<typename... U,
        typename std::enable_if_t<(sizeof...(T) > 0 && sizeof...(U) == sizeof...(T)),bool> = true>
      explicit constexpr HybridTreePath(U... t)
        : _data(t...) // we assume that all arguments are convertible to the types T...
      {
        [[maybe_unused]] constexpr bool check =
          (... && Impl::check_storage_type(MetaType<T>()) );
      }
 
      [[nodiscard]] constexpr static index_sequence enumerate()
      {
        return {};
      }
 
      [[nodiscard]] constexpr static std::size_t size()
      {
        return sizeof...(T);
      }
 
      [[nodiscard]] constexpr static std::size_t max_size()
      {
        return size();
      }
 
      template<std::size_t i,
        std::enable_if_t<(sizeof...(T) > i),bool> = true>
      [[nodiscard]] constexpr auto operator[](Dune::index_constant<i>) const
      {
        return std::get<i>(_data);
      }
 
      [[nodiscard]] constexpr std::size_t operator[](std::size_t pos) const
      {
        std::size_t entry = 0;
        Dune::Hybrid::forEach(enumerate(), [&] (auto i) {
            if (i==pos)
              entry = this->element(i);
        });
        return entry;
      }
 
      template<std::size_t i,
        std::enable_if_t<(sizeof...(T) > i),bool> = true>
      [[nodiscard]] constexpr auto element(Dune::index_constant<i> pos = {}) const
      {
        return std::get<i>(_data);
      }
 
      [[nodiscard]] constexpr std::size_t element(std::size_t pos) const
      {
        std::size_t entry = 0;
        Dune::Hybrid::forEach(enumerate(), [&] (auto i) {
            if (i==pos)
              entry = this->element(i);
        });
        return entry;
      }
 
      template<std::size_t n = sizeof...(T),
        std::enable_if_t<(n > 0 && n == sizeof...(T)),bool> = true>
      [[nodiscard]] constexpr auto front() const
      {
        return std::get<0>(_data);
      }
 
      template<std::size_t n = sizeof...(T),
        std::enable_if_t<(n > 0 && n == sizeof...(T)),bool> = true>
      [[nodiscard]] constexpr auto back() const
      {
        return std::get<n-1>(_data);
      }
 
#ifndef DOXYGEN
 
      // I can't be bothered to make all the external accessors friends of HybridTreePath,
      // so we'll only hide the data tuple from the user in Doxygen.
 
      using Data = std::tuple<T...>;
      Data _data;
 
#endif // DOXYGEN
 
    };
 
 
    template<typename... T>
    [[nodiscard]] constexpr auto makeTreePath(const T... t)
    {
      // check that all entries are based on std::size_t
      static_assert((... && Impl::check_size_t<T>()),
        "HybridTreePath indices must be of type std::size_t or std::integral_constant<std::size_t,v>");
      return HybridTreePath<T...>(t...);
    }
 
 
    template<typename... T>
    [[nodiscard]] constexpr auto hybridTreePath(const T&... t)
    {
      return makeTreePath(Impl::cast_size_t(t)...);
    }
 
 
    template<typename... T>
    [[nodiscard]] constexpr auto treePath(const T&... t)
    {
      return makeTreePath(Impl::cast_size_t(t)...);
    }
 
 
    template<typename... T>
    [[nodiscard]] constexpr std::size_t treePathSize(const HybridTreePath<T...>&)
    {
      return sizeof...(T);
    }
 
 
    template<std::size_t i, typename... T>
    [[nodiscard]] constexpr auto treePathEntry(const HybridTreePath<T...>& tp, index_constant<i> = {})
      -> typename std::decay<decltype(std::get<i>(tp._data))>::type
    {
      return std::get<i>(tp._data);
    }
 
 
    template<std::size_t i,typename... T>
    [[nodiscard]] constexpr std::size_t treePathIndex(const HybridTreePath<T...>& tp, index_constant<i> = {})
    {
      return std::get<i>(tp._data);
    }
 
 
    template<typename... T>
    [[nodiscard]] constexpr auto back(const HybridTreePath<T...>& tp)
      -> decltype(tp.back())
    {
      return tp.back();
    }
 
 
    template<typename... T>
    [[nodiscard]] constexpr auto front(const HybridTreePath<T...>& tp)
      -> decltype(tp.front())
    {
      return tp.front();
    }
 
 
    template<typename... T>
    [[nodiscard]] constexpr HybridTreePath<T...,std::size_t> push_back(const HybridTreePath<T...>& tp, std::size_t i)
    {
      return HybridTreePath<T...,std::size_t>(std::tuple_cat(tp._data,std::make_tuple(i)));
    }
 
 
    template<std::size_t i, typename... T>
    [[nodiscard]] constexpr HybridTreePath<T...,index_constant<i>> push_back(const HybridTreePath<T...>& tp, index_constant<i> i_ = {})
    {
      return HybridTreePath<T...,index_constant<i> >(std::tuple_cat(tp._data,std::make_tuple(i_)));
    }
 
 
    template<typename... T>
    [[nodiscard]] constexpr HybridTreePath<std::size_t,T...> push_front(const HybridTreePath<T...>& tp, std::size_t element)
    {
      return HybridTreePath<std::size_t,T...>(std::tuple_cat(std::make_tuple(element),tp._data));
    }
 
 
    template<std::size_t i, typename... T>
    [[nodiscard]] constexpr HybridTreePath<index_constant<i>,T...> push_front(const HybridTreePath<T...>& tp, index_constant<i> _i = {})
    {
      return HybridTreePath<index_constant<i>,T...>(std::tuple_cat(std::make_tuple(_i),tp._data));
    }
 
 
    template<typename I, typename... T, std::enable_if_t<(sizeof...(T) > 0),bool> = true>
    [[nodiscard]] constexpr auto accumulate_back(const HybridTreePath<T...>& tp, I i) {
      using ::Dune::Hybrid::plus;
      return push_back(pop_back(tp), plus(back(tp), i));
    }
 
 
 
    template<typename I, typename... T, std::enable_if_t<(sizeof...(T) > 0),bool> = true>
    [[nodiscard]] constexpr auto accumulate_front(const HybridTreePath<T...>& tp, I i) {
      using ::Dune::Hybrid::plus;
      return push_front(pop_front(tp), plus(front(tp), i));
    }
 
    template<class... Head, class... Other>
    [[nodiscard]] constexpr auto join(const HybridTreePath<Head...>& head, const Other&... tail) {
      return TypeTree::HybridTreePath{std::tuple_cat(head._data, tail._data...)};
    }
 
    template<class... T>
    [[nodiscard]] constexpr auto reverse(const HybridTreePath<T...>& tp) {
      constexpr std::size_t size = sizeof...(T);
      return unpackIntegerSequence([&](auto... i){
        return treePath(tp[index_constant<size-i-1>{}] ...);
      }, std::make_index_sequence<size>{});
    }
 
 
    template <class... T, std::enable_if_t<(sizeof...(T) > 0),bool> = true>
    [[nodiscard]] constexpr auto pop_front(const HybridTreePath<T...>& tp)
    {
      return unpackIntegerSequence([&](auto... i){
        return HybridTreePath{std::make_tuple(std::get<i+1>(tp._data)...)};
      }, std::make_index_sequence<(sizeof...(T) - 1)>{});
    }
 
 
    template <class... T, std::enable_if_t<(sizeof...(T) > 0),bool> = true>
    [[nodiscard]] constexpr auto pop_back(const HybridTreePath<T...>& tp)
    {
      return unpackIntegerSequence([&](auto... i){
        return HybridTreePath{std::make_tuple(std::get<i>(tp._data)...)};
      }, std::make_index_sequence<(sizeof...(T) - 1)>{});
    }
 
 
    template <class... S, class... T>
    [[nodiscard]] constexpr bool operator==(
      const HybridTreePath<S...>& lhs,
      const HybridTreePath<T...>& rhs)
    {
      if constexpr (sizeof...(S) == sizeof...(T)) {
        if constexpr ((Dune::IsInteroperable<S,T>::value &&...)) {
          return unpackIntegerSequence([&](auto... i){
            return ((std::get<i>(lhs._data) == std::get<i>(rhs._data)) &&...);
          }, std::make_index_sequence<(sizeof...(S))>{});
        } else {
          return false;
        }
      } else {
        return false;
      }
    }
 
 
    template <class S, S... lhs, class T, T... rhs>
    [[nodiscard]] constexpr auto operator==(
      const HybridTreePath<std::integral_constant<S,lhs>...>&,
      const HybridTreePath<std::integral_constant<T,rhs>...>&)
    {
      return std::bool_constant<hybridTreePath(lhs...) == hybridTreePath(rhs...)>{};
    }
 
 
    template <class... S, class... T>
    [[nodiscard]] constexpr auto operator!=(
      const HybridTreePath<S...>& lhs,
      const HybridTreePath<T...>& rhs)
    {
      return !(lhs == rhs);
    }
 
    template <class S, S... lhs, class T, T... rhs>
    [[nodiscard]] constexpr auto operator!=(
      const HybridTreePath<std::integral_constant<S,lhs>...>&,
      const HybridTreePath<std::integral_constant<T,rhs>...>&)
    {
      return std::bool_constant<hybridTreePath(lhs...) != hybridTreePath(rhs...)>{};
    }
 
 
    inline namespace Literals {
 
 
    template <char... digits>
    constexpr auto operator""_tp()
    {
      using namespace Dune::Indices::Literals;
      return hybridTreePath(operator""_ic<digits...>());
    }
 
    } // end namespace Literals
 
 
    template<std::size_t... i>
    struct TreePathSize<HybridTreePath<index_constant<i>...> >
      : public index_constant<sizeof...(i)>
    {};
 
 
    template<std::size_t k, std::size_t... i>
    struct TreePathPushBack<HybridTreePath<index_constant<i>...>,k>
    {
      typedef HybridTreePath<index_constant<i>...,index_constant<k>> type;
    };
 
    template<std::size_t k, std::size_t... i>
    struct TreePathPushFront<HybridTreePath<index_constant<i>...>,k>
    {
      typedef HybridTreePath<index_constant<k>,index_constant<i>...> type;
    };
 
    template<std::size_t k>
    struct TreePathBack<HybridTreePath<index_constant<k>>>
      : public index_constant<k>
    {};
 
    template<std::size_t j, std::size_t k, std::size_t... l>
    struct TreePathBack<HybridTreePath<index_constant<j>,index_constant<k>,index_constant<l>...>>
      : public TreePathBack<HybridTreePath<index_constant<k>,index_constant<l>...>>
    {};
 
    template<std::size_t k, std::size_t... i>
    struct TreePathFront<HybridTreePath<index_constant<k>,index_constant<i>...>>
      : public index_constant<k>
    {};
 
    template<std::size_t k, std::size_t... i>
    struct TreePathPopBack<HybridTreePath<index_constant<k>>,i...>
    {
      typedef HybridTreePath<index_constant<i>...> type;
    };
 
    template<std::size_t j,
             std::size_t k,
             std::size_t... l,
             std::size_t... i>
    struct TreePathPopBack<HybridTreePath<index_constant<j>,index_constant<k>,index_constant<l>...>,i...>
      : public TreePathPopBack<HybridTreePath<index_constant<k>,index_constant<l>...>,i...,j>
    {};
 
    template<std::size_t k, std::size_t... i>
    struct TreePathPopFront<HybridTreePath<index_constant<k>,index_constant<i>...> >
    {
      typedef HybridTreePath<index_constant<i>...> type;
    };
 
    template<std::size_t... i, std::size_t... k>
    struct TreePathConcat<HybridTreePath<index_constant<i>...>,HybridTreePath<index_constant<k>...> >
    {
      typedef HybridTreePath<index_constant<i>...,index_constant<k>...> type;
    };
 
#ifndef DOXYGEN
 
    namespace impl {
 
      // end of recursion
      template<std::size_t i, typename... T>
      typename std::enable_if<
        (i == sizeof...(T))
        >::type
      print_hybrid_tree_path(std::ostream& os, const HybridTreePath<T...>& tp, index_constant<i> _i)
      {}
 
      // print current entry and recurse
      template<std::size_t i, typename... T>
      typename std::enable_if<
        (i < sizeof...(T))
        >::type
      print_hybrid_tree_path(std::ostream& os, const HybridTreePath<T...>& tp, index_constant<i> _i)
      {
        os << treePathIndex(tp,_i) << " ";
        print_hybrid_tree_path(os,tp,index_constant<i+1>{});
      }
 
    } // namespace impl
 
#endif // DOXYGEN
 
    template<typename... T>
    std::ostream& operator<<(std::ostream& os, const HybridTreePath<T...>& tp)
    {
      os << "HybridTreePath< ";
      impl::print_hybrid_tree_path(os, tp, index_constant<0>{});
      os << ">";
      return os;
    }
 
    template<std::size_t... i>
    using StaticTreePath = HybridTreePath<Dune::index_constant<i>...>;
 
 
  } // namespace TypeTree
} //namespace Dune
 
#endif // DUNE_TYPETREE_TREEPATH_HH