hybridmultiindex.hh

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// -*- 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: LicenseRef-GPL-2.0-only-with-DUNE-exception OR LGPL-3.0-or-later

#ifndef DUNE_COMMON_HYBRIDMULTIINDEX_HH
#define DUNE_COMMON_HYBRIDMULTIINDEX_HH

#include <cstddef>
#include <cassert>
#include <iostream>
#include <type_traits>

#include <dune/common/typetraits.hh>
#include <dune/common/indices.hh>
#include <dune/common/hybridutilities.hh>

namespace Dune {

  // The Impl namespace collects some free standing functions helper functions
  namespace Impl {

    template<class T>
    constexpr bool isHybridSizeT()
    {
      if constexpr (std::is_same_v<T, std::size_t>)
        return true;
      else
      {
        if constexpr (requires { T::value; })
          return std::is_same_v<T, std::integral_constant<std::size_t, T::value>>;
        else
          return false;
      }
    }

    template<class T>
    constexpr auto castToHybridSizeT(T t)
    {
      if constexpr (Dune::IsIntegralConstant<T>::value)
      {
        using VT = typename T::value_type;
        static_assert(
          std::is_convertible_v<VT,std::size_t> &&
          std::is_integral_v<VT> &&
          T::value >= 0,
          "HybridMultiIndex indices must be convertible to std::size_t or std::integral_constant<std::size_t,v>");
        return std::integral_constant<std::size_t, T::value>{};
      }
      if constexpr (std::is_integral_v<T>)
      {
        static_assert(
          std::is_convertible_v<T,std::size_t> &&
          std::is_integral_v<T>,
          "HybridMultiIndex indices must be convertible to std::size_t or std::integral_constant<std::size_t,v>");
        assert(t >= 0 &&
          "HybridMultiIndex indices must be convertible to std::size_t or std::integral_constant<std::size_t,v>");
        return std::size_t(t);
      }
      if constexpr (not (Dune::IsIntegralConstant<T>::value or std::is_integral_v<T>))
      {
        return std::size_t(0);
      }
    }

  }

  template<typename... T>
  class HybridMultiIndex
  {

    // make sure that all indices use std::size_t as the underlying number type
    static_assert((... && Impl::isHybridSizeT<T>()),
      "HybridMultiIndex index storage must be std::size_t or std::integral_constant<std::size_t,v>");

  public:

    using index_sequence = std::index_sequence_for<T...>;

    constexpr HybridMultiIndex() = default;

    constexpr HybridMultiIndex(const HybridMultiIndex& tp) = default;

    constexpr HybridMultiIndex(HybridMultiIndex&& tp) = default;

    constexpr HybridMultiIndex& operator=(const HybridMultiIndex& tp) = default;

    constexpr HybridMultiIndex& operator=(HybridMultiIndex&& tp) = default;

    explicit constexpr HybridMultiIndex(std::tuple<T...> t)
      : _data(t)
    {}

    template<typename... I>
    requires ((sizeof...(T) > 0 && sizeof...(I) == sizeof...(T))
              and ((std::is_integral_v<I> or Dune::IsIntegralConstant<I>::value) && ...))
    explicit constexpr HybridMultiIndex(I... i)
      : _data(Impl::castToHybridSizeT(i)...) // we assume that all arguments are convertible to the types 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>
    requires (sizeof...(T) > i)
    [[nodiscard]] constexpr auto get() const
    {
      return std::get<i>(_data);
    }

    template<std::size_t i>
    requires (sizeof...(T) > i)
    [[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)[i];
      });
      return entry;
    }

    template<std::size_t i>
    requires (sizeof...(T) > i)
    [[deprecated("Method will be removed after Dune 2.11. Use operator[] instead.")]]
    [[nodiscard]] constexpr auto element(Dune::index_constant<i> pos = {}) const
    {
      return std::get<i>(_data);
    }

    [[deprecated("Method will be removed after Dune 2.11. Use operator[] instead.")]]
    [[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)[i];
      });
      return entry;
    }

    template<std::size_t n = sizeof...(T)>
    requires (n > 0 && n == sizeof...(T))
    [[nodiscard]] constexpr auto front() const
    {
      return std::get<0>(_data);
    }

    template<std::size_t n = sizeof...(T)>
    requires (n > 0 && n == sizeof...(T))
    [[nodiscard]] constexpr auto back() const
    {
      return std::get<n-1>(_data);
    }

  private:

    template<class... Head, class... Other>
    friend constexpr auto join(const HybridMultiIndex<Head...>&, const Other&...);

    std::tuple<T...> _data;

  };

  template<typename... I>
  requires (((std::is_integral_v<I> or Dune::IsIntegralConstant<I>::value) && ...))
  HybridMultiIndex(I... i) -> HybridMultiIndex<decltype(Impl::castToHybridSizeT(i))...>;

  template<typename... I>
  HybridMultiIndex(std::tuple<I...>) -> HybridMultiIndex<I...>;


  template<typename... T>
  [[nodiscard]] constexpr auto back(const HybridMultiIndex<T...>& tp)
    -> decltype(tp.back())
  {
    return tp.back();
  }


  template<typename... T>
  [[nodiscard]] constexpr auto front(const HybridMultiIndex<T...>& tp)
    -> decltype(tp.front())
  {
    return tp.front();
  }


  template<typename... T>
  [[nodiscard]] constexpr HybridMultiIndex<T...,std::size_t> push_back(const HybridMultiIndex<T...>& tp, std::size_t i)
  {
    return unpackIntegerSequence([&](auto... j){
      return HybridMultiIndex(tp[j] ..., i);
    }, tp.enumerate());
  }


  template<std::size_t i, typename... T>
  [[nodiscard]] constexpr HybridMultiIndex<T...,index_constant<i>> push_back(const HybridMultiIndex<T...>& tp, index_constant<i> iConstant = {})
  {
    return unpackIntegerSequence([&](auto... j){
      return HybridMultiIndex(tp[j] ..., iConstant);
    }, tp.enumerate());
  }


  template<typename... T>
  [[nodiscard]] constexpr HybridMultiIndex<std::size_t,T...> push_front(const HybridMultiIndex<T...>& tp, std::size_t i)
  {
    return unpackIntegerSequence([&](auto... j){
      return HybridMultiIndex(i, tp[j] ...);
    }, tp.enumerate());
  }


  template<std::size_t i, typename... T>
  [[nodiscard]] constexpr HybridMultiIndex<index_constant<i>,T...> push_front(const HybridMultiIndex<T...>& tp, index_constant<i> iConstant = {})
  {
    return unpackIntegerSequence([&](auto... j){
      return HybridMultiIndex(iConstant, tp[j] ...);
    }, tp.enumerate());
  }


  template<typename I, typename... T>
  requires (sizeof...(T) > 0)
  [[nodiscard]] constexpr auto accumulate_back(const HybridMultiIndex<T...>& tp, I i) {
    using ::Dune::Hybrid::plus;
    return push_back(pop_back(tp), plus(back(tp), i));
  }



  template<typename I, typename... T>
  requires (sizeof...(T) > 0)
  [[nodiscard]] constexpr auto accumulate_front(const HybridMultiIndex<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 HybridMultiIndex<Head...>& head, const Other&... tail) {
    return Dune::HybridMultiIndex{std::tuple_cat(head._data, tail._data...)};
  }

  template<class... T>
  [[nodiscard]] constexpr auto reverse(const HybridMultiIndex<T...>& tp) {
    constexpr std::size_t size = sizeof...(T);
    return unpackIntegerSequence([&](auto... i){
      return HybridMultiIndex(tp[index_constant<size-i-1>{}] ...);
    }, std::make_index_sequence<size>{});
  }


  template <class... T>
  requires (sizeof...(T) > 0)
  [[nodiscard]] constexpr auto pop_front(const HybridMultiIndex<T...>& tp)
  {
    return unpackIntegerSequence([&](auto... i){
      return HybridMultiIndex{std::make_tuple(tp[Dune::index_constant<i+1>{}]...)};
    }, std::make_index_sequence<(sizeof...(T) - 1)>{});
  }


  template <class... T>
  requires (sizeof...(T) > 0)
  [[nodiscard]] constexpr auto pop_back(const HybridMultiIndex<T...>& tp)
  {
    return unpackIntegerSequence([&](auto... i){
      return HybridMultiIndex{std::make_tuple(tp[i]...)};
    }, std::make_index_sequence<(sizeof...(T) - 1)>{});
  }


  template <class... S, class... T>
  [[nodiscard]] constexpr bool operator==(
    const HybridMultiIndex<S...>& lhs,
    const HybridMultiIndex<T...>& rhs)
  {
    if constexpr (sizeof...(S) == sizeof...(T)) {
      if constexpr ((Dune::IsInteroperable<S,T>::value &&...)) {
        return unpackIntegerSequence([&](auto... i){
          return ((lhs[i] == rhs[i]) &&...);
        }, lhs.enumerate());
      } else {
        return false;
      }
    } else {
      return false;
    }
  }


  template <class S, S... lhs, class T, T... rhs>
  [[nodiscard]] constexpr auto operator==(
    const HybridMultiIndex<std::integral_constant<S,lhs>...>&,
    const HybridMultiIndex<std::integral_constant<T,rhs>...>&)
  {
    // If we directly put the expression into std::bool_constant,
    // gcc-10 deduced the return type of this method as `HybridMultiIndex<>.
    constexpr auto result = (HybridMultiIndex(lhs...) == HybridMultiIndex(rhs...));
    return std::bool_constant<result>{};
  }


  template <class... S, class... T>
  [[nodiscard]] constexpr auto operator!=(
    const HybridMultiIndex<S...>& lhs,
    const HybridMultiIndex<T...>& rhs)
  {
    return !(lhs == rhs);
  }

  template <class S, S... lhs, class T, T... rhs>
  [[nodiscard]] constexpr auto operator!=(
    const HybridMultiIndex<std::integral_constant<S,lhs>...>&,
    const HybridMultiIndex<std::integral_constant<T,rhs>...>&)
  {
    // If we directly put the expression into std::bool_constant,
    // gcc-10 deduced the return type of this method as `HybridMultiIndex<>.
    constexpr auto result = (HybridMultiIndex(lhs...) != HybridMultiIndex(rhs...));
    return std::bool_constant<result>{};
  }

  template<typename... T>
  std::ostream& operator<<(std::ostream& os, const HybridMultiIndex<T...>& tp)
  {
    os << "HybridMultiIndex< ";
    Dune::Hybrid::forEach(tp, [&] (auto tp_i) {
      os << tp_i << " ";
    });
    os << ">";
    return os;
  }

} //namespace Dune



// Implement the tuple-protocol for HybridMultiIndex
namespace std {

  template<typename... T>
  struct tuple_size<Dune::HybridMultiIndex<T...>> : public std::integral_constant<std::size_t,sizeof...(T)> {};

  template <size_t i, typename... T>
  struct tuple_element<i, Dune::HybridMultiIndex<T...> >
  {
    using type = std::tuple_element_t<i, std::tuple<T...> >;
  };

}


#endif // DUNE_COMMON_HYBRIDMULTIINDEX_HH