tpl_ca_multi_field_rule.H

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
 
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  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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*/
 
#ifndef TPL_CA_MULTI_FIELD_RULE_H
#define TPL_CA_MULTI_FIELD_RULE_H
 
#include <concepts>
#include <cstddef>
#include <tuple>
#include <type_traits>
#include <utility>
 
#include <ca-traits.H>
#include <tpl_ca_concepts.H>
 
namespace Aleph {
namespace CA {
 
namespace ca_mf_rule_detail {
 
template <typename T>
struct as_neighbor_view
{
  using type = Neighbor_View<T>;
};
 
template <typename Tuple>
struct neighbor_view_tuple;
 
template <typename... Fields>
struct neighbor_view_tuple<std::tuple<Fields...>>
{
  using type = std::tuple<Neighbor_View<Fields>...>;
};
 
}  // namespace ca_mf_rule_detail
 
template <typename FieldsTuple>
using Field_Neighbor_Views_Tuple =
  typename ca_mf_rule_detail::neighbor_view_tuple<FieldsTuple>::type;
 
template <typename R, typename FieldsTuple>
concept BasicMultiFieldRule
  = requires(const R &r, const FieldsTuple &cur, const Field_Neighbor_Views_Tuple<FieldsTuple> &nb) {
      { r(cur, nb) } -> std::convertible_to<FieldsTuple>;
    };
 
template <typename R, typename FieldsTuple, std::size_t Rank>
concept ContextualMultiFieldRule = requires(const R &r,
                                            const FieldsTuple &cur,
                                            const Field_Neighbor_Views_Tuple<FieldsTuple> &nb,
                                            const Cell_Context<Rank> &ctx) {
  { r(cur, nb, ctx) } -> std::convertible_to<FieldsTuple>;
};
 
template <typename R, typename FieldsTuple, std::size_t Rank>
concept MultiFieldRuleLike
  = BasicMultiFieldRule<R, FieldsTuple> or ContextualMultiFieldRule<R, FieldsTuple, Rank>;
 
template <typename Rule, typename FieldsTuple, std::size_t Rank>
[[nodiscard]] inline FieldsTuple apply_multi_field_rule(const Rule &r,
                                                        const FieldsTuple &cur,
                                                        const Field_Neighbor_Views_Tuple<FieldsTuple> &nb,
                                                        const Cell_Context<Rank> &ctx)
{
  if constexpr (requires { r(cur, nb, ctx); })
    return r(cur, nb, ctx);
  else
    return r(cur, nb);
}
 
// =======================================================================
// Field_Slice_Rule
// =======================================================================
 
template <std::size_t I, typename Inner>
class Field_Slice_Rule
{
  Inner inner_;
 
public:
  constexpr explicit Field_Slice_Rule(Inner inner) : inner_(std::move(inner)) {}
 
  template <typename FieldsTuple>
  [[nodiscard]] FieldsTuple operator()(const FieldsTuple &cur,
                                       const Field_Neighbor_Views_Tuple<FieldsTuple> &nb) const
  {
    static_assert(I < std::tuple_size_v<FieldsTuple>, "Field_Slice_Rule: I out of range");
    FieldsTuple out = cur;
    std::get<I>(out) = inner_(std::get<I>(cur), std::get<I>(nb));
    return out;
  }
 
  template <typename FieldsTuple, std::size_t Rank>
  [[nodiscard]] FieldsTuple operator()(const FieldsTuple &cur,
                                       const Field_Neighbor_Views_Tuple<FieldsTuple> &nb,
                                       const Cell_Context<Rank> &ctx) const
  {
    static_assert(I < std::tuple_size_v<FieldsTuple>, "Field_Slice_Rule: I out of range");
    FieldsTuple out = cur;
    if constexpr (requires { inner_(std::get<I>(cur), std::get<I>(nb), ctx); })
      std::get<I>(out) = inner_(std::get<I>(cur), std::get<I>(nb), ctx);
    else
      std::get<I>(out) = inner_(std::get<I>(cur), std::get<I>(nb));
    return out;
  }
};
 
}  // namespace CA
}  // namespace Aleph
 
#endif  // TPL_CA_MULTI_FIELD_RULE_H