containerdescriptors.hh

// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set et ts=4 sw=2 sts=2:
 
// SPDX-FileCopyrightText: Copyright © DUNE Project contributors, see file AUTHORS.md
// SPDX-License-Identifier: LicenseRef-GPL-2.0-only-with-DUNE-exception OR LGPL-3.0-or-later
 
#ifndef DUNE_FUNCTIONS_FUNCTIONSPACEBASES_CONTAINERDESCRIPTORS_HH
#define DUNE_FUNCTIONS_FUNCTIONSPACEBASES_CONTAINERDESCRIPTORS_HH
 
#include <array>
#include <cassert>
#include <functional>
#include <type_traits>
#include <vector>
 
#include <dune/common/filledarray.hh>
#include <dune/common/tuplevector.hh>
#include <dune/common/typeutilities.hh>
 
#include <dune/functions/common/type_traits.hh>
#include <dune/functions/functionspacebases/basistags.hh>
 
namespace Dune::Functions {
namespace ContainerDescriptors {
 
struct Unknown {};
 
} // end namespace ContainerDescriptors
 
namespace Impl {
 
template<class PreBasis>
auto containerDescriptorImpl(const PreBasis& preBasis, Dune::PriorityTag<1>)
  -> decltype(preBasis.containerDescriptor())
{
  return preBasis.containerDescriptor();
}
 
template<class PreBasis>
auto containerDescriptorImpl(const PreBasis& preBasis, Dune::PriorityTag<0>)
{
  return ContainerDescriptors::Unknown{};
}
 
} // end namespace Impl
 
template<class PreBasis>
auto containerDescriptor(const PreBasis& preBasis)
{
  return Impl::containerDescriptorImpl(preBasis, Dune::PriorityTag<2>{});
}
 
 
namespace ContainerDescriptors {
 
struct Value
{
  template<class Index>
  Value operator[] (const Index&) const { return {}; }
 
  static constexpr std::size_t size () { return 0; }
};
 
template<class... Children>
using Tuple = Dune::TupleVector<Children...>;
 
template<class Child0, class... Children,
  std::enable_if_t<(sizeof...(Children) > 0), int> = 0,
  std::enable_if_t<(...|| (not std::is_same_v<Child0, Children>)), int> = 0>
auto makeDescriptor (Child0 child0, Children... children)
{
  using Descriptor = Tuple<Child0,Children...>;
  return Descriptor{std::move(child0),std::move(children)...};
}
 
 
template<class Child, std::size_t n>
using Array = std::array<Child, n>;
 
template<class Child0, class... Children,
  std::enable_if_t<(std::is_same_v<Child0, Children> &&...), int> = 0>
auto makeDescriptor (Child0 child, Children... children)
{
  using Descriptor = Array<Child0,1+sizeof...(Children)>;
  return Descriptor{std::move(child),std::move(children)...};
}
 
 
template<class Child>
using Vector = std::vector<Child>;
 
template<class Child, std::size_t n>
struct UniformArray
{
  template<class C = Child,
    std::enable_if_t<std::is_default_constructible_v<C>, int> = 0>
  UniformArray ()
    : child_{}
  {}
 
  explicit UniformArray (Child child)
    : child_{std::move(child)}
  {}
 
  template<class Index>
  const Child& operator[] (const Index& /*i*/) const { return child_; }
 
  static constexpr std::size_t size () { return n; }
 
private:
  Child child_;
};
 
template<std::size_t n>
using FlatArray = UniformArray<Value,n>;
 
template<class Child, std::size_t n>
auto makeUniformDescriptor (std::integral_constant<std::size_t,n>, Child child)
{
  return UniformArray<Child,n>{std::move(child)};
}
 
 
template<class Child>
struct UniformVector
{
  template<class C = Child,
    std::enable_if_t<std::is_default_constructible_v<C>, int> = 0>
  explicit UniformVector (std::size_t size)
    : size_{size}
    , child_{}
  {}
 
  UniformVector (std::size_t size, Child child)
    : size_{size}
    , child_{std::move(child)}
  {}
 
  template<class Index>
  const Child& operator[] (const Index& /*i*/) const { return child_; }
 
  std::size_t size () const { return size_; }
 
private:
  std::size_t size_;
  Child child_;
};
 
using FlatVector = UniformVector<Value>;
 
template<class Child>
auto makeUniformDescriptor (std::size_t n, Child child)
{
  return UniformVector<Child>{n,std::move(child)};
}
 
namespace Impl {
 
template<class InnerFunc, class LeafFunc>
struct TreeTransform
{
  TreeTransform (const InnerFunc& innerFunc, const LeafFunc& leafFunc)
    : innerFunc_(innerFunc)
    , leafFunc_(leafFunc)
  {}
 
  Unknown operator() (const Unknown& tree) const
  {
    return tree;
  }
 
  auto operator() (const Value& tree) const
  {
    return leafFunc_(tree);
  }
 
  template<class... V>
  auto operator() (const Tuple<V...>& tree) const
  {
    return unpackIntegerSequence([&](auto... ii) {
      return makeDescriptor(innerFunc_(tree[ii])...);
    }, std::make_index_sequence<sizeof...(V)>());
  }
 
  template<class V, std::size_t n>
  auto operator() (const Array<V,n>& tree) const
  {
    return unpackIntegerSequence([&](auto... ii) {
      return makeDescriptor(innerFunc_(tree[ii])...);
    }, std::make_index_sequence<n>());
  }
 
  template<class V>
  auto operator() (const Vector<V>& tree) const
  {
    using W = decltype(innerFunc_(tree[0]));
    Vector<W> result;
    result.reserve(tree.size());
    for (std::size_t i = 0; i < tree.size(); ++i)
      result.emplace_back(innerFunc_(tree[i]));
    return result;
  }
 
  template<class V, std::size_t n>
  auto operator() (const UniformArray<V,n>& tree) const
  {
    return makeUniformDescriptor(Dune::index_constant<n>{}, innerFunc_(tree[0]));
  }
 
  template<class V>
  auto operator() (const UniformVector<V>& tree) const
  {
    return makeUniformDescriptor(tree.size(), innerFunc_(tree[0]));
  }
 
private:
  InnerFunc innerFunc_;
  LeafFunc leafFunc_;
};
 
 
template<class Size, class T>
auto appendToTree (Size s, const T& tree)
{
  auto transform = TreeTransform(
    [s](auto&& node) { return appendToTree(s, node); },
    [s](auto&& node) { return makeUniformDescriptor(s, node); });
  return transform(tree);
}
 
} // end namespace Impl
} // end namespace ContainerDescriptors
} // end namespace Dune::Functions
 
#endif // DUNE_FUNCTIONS_FUNCTIONSPACEBASES_CONTAINERDESCRIPTORS_HH