type_list.h

/******************************************************************************
The MIT License(MIT)
 
Embedded Template Library.
https://github.com/ETLCPP/etl
https://www.etlcpp.com
 
Copyright(c) 2025 John Wellbelove
 
Permission is hereby granted, free of charge, to any person obtaining a copy
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The above copyright notice and this permission notice shall be included in all
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******************************************************************************/
 
#ifndef ETL_TYPE_LIST_INCLUDED
#define ETL_TYPE_LIST_INCLUDED
 
#include "platform.h"
 
#include "algorithm.h"
#include "index_of_type.h"
#include "integral_limits.h"
#include "static_assert.h"
#include "type_traits.h"
#include "utility.h"
#include "largest.h"
 
#if ETL_USING_CPP11
namespace etl
{
  //***************************************************************************
  //***************************************************************************
  static ETL_CONSTANT size_t type_list_npos = etl::integral_limits<size_t>::max;
 
  //***************************************************************************
  //***************************************************************************
  template <typename... TTypes>
  struct type_list;
 
  //***************************************************************************
  //***************************************************************************
  template <>
  struct type_list<>
  {
    static constexpr size_t size = 0U;
 
    using index_sequence_type = etl::make_index_sequence<0>; 
 
  private:
 
    type_list() ETL_DELETE;
    type_list(const type_list&) ETL_DELETE;
    type_list& operator =(const type_list&) ETL_DELETE;
  };
 
  namespace private_type_list
  {
    // helper to solve the issue that recursed-rest can't be put directly in type_list::tail definition
    template <typename... TTypes>
    struct recursion_helper
    {
      using type = type_list<TTypes...>;
    };
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename THead, typename... TTail>
  struct type_list<THead, TTail...> : type_list<TTail...>
  {
    using head = THead;
    using tail = typename private_type_list::recursion_helper<TTail...>::type;
 
    static constexpr size_t size = sizeof...(TTail) + 1U;
 
    using index_sequence_type = etl::make_index_sequence<sizeof...(TTail) + 1U>; 
 
  private:
 
    type_list() ETL_DELETE;
    type_list(const type_list&) ETL_DELETE;
    type_list& operator =(const type_list&) ETL_DELETE;
  };
 
  //***************************************************************************
  //***************************************************************************
  template <typename THead>
  struct type_list<THead> : type_list<>
  {
    using head = THead;
    using tail = typename private_type_list::recursion_helper<>::type;
 
    static constexpr size_t size = 1U;
 
    using index_sequence_type = etl::make_index_sequence<1>; 
 
  private:
 
    type_list() ETL_DELETE;
    type_list(const type_list&) ETL_DELETE;
    type_list& operator =(const type_list&) ETL_DELETE;
  };
 
  //***************************************************************************
  //***************************************************************************
  template <typename TTypes>
  struct type_list_size;
 
  template <typename... TTypes>
  struct type_list_size<etl::type_list<TTypes...>> : public etl::integral_constant<size_t, sizeof...(TTypes)>
  {
  };
 
#if ETL_USING_CPP17
  template <typename... TTypes>
  inline constexpr size_t type_list_size_v = type_list_size<etl::type_list<TTypes...>>::value;
#endif
 
  //***************************************************************************
  //***************************************************************************
  template <typename TTypeList, size_t Index>
  struct type_list_type_at_index
  {
    ETL_STATIC_ASSERT(Index < type_list_size<TTypeList>::value,              "etl::type_list_type_at_index out of range");
    ETL_STATIC_ASSERT((etl::is_base_of<etl::type_list<>, TTypeList>::value), "TTypeList must be an etl::type_list");
 
    using type = typename type_list_type_at_index<typename TTypeList::tail, Index - 1>::type;
  };
 
  template <typename TTypeList>
  struct type_list_type_at_index<TTypeList, 0>
  {
    using type = typename TTypeList::head;
  };
 
  template <typename TTypeList, size_t Index>
  using type_list_type_at_index_t = typename type_list_type_at_index<TTypeList, Index>::type;
 
  //***************************************************************************
  //***************************************************************************
  template <typename TTypeList, typename T>
  struct type_list_index_of_type
    : public etl::integral_constant<size_t, etl::is_same<typename TTypeList::head, T>::value ? 0 :
                                            (type_list_index_of_type<typename TTypeList::tail, T>::value == etl::type_list_npos ? etl::type_list_npos : 
                                                                                                                                  type_list_index_of_type<typename TTypeList::tail, T>::value + 1)>
  {
    ETL_STATIC_ASSERT((etl::is_base_of<etl::type_list<>, TTypeList>::value), "TTypeList must be an etl::type_list");
  };
 
  template <typename T>
  struct type_list_index_of_type<type_list<>, T>
    : public etl::integral_constant<size_t, etl::type_list_npos>
  {
  };
 
#if ETL_USING_CPP17
  template <typename TTypeList, typename T>
  inline constexpr size_t type_list_index_of_v = etl::type_list_index_of_type<TTypeList, T>::value;
#endif
 
  //***************************************************************************
  //***************************************************************************
  template <typename T, typename TTypes>
  struct type_list_contains;
 
  template <typename T, typename... TTypes>
  struct type_list_contains<etl::type_list<TTypes...>, T>
    : public etl::integral_constant<bool, etl::is_one_of<T, TTypes...>::value>
  {
  };
 
  template <typename T>
  struct type_list_contains<type_list<>, T>
    : public etl::integral_constant<bool, false>
  {
  };
 
#if ETL_USING_CPP17
  template <typename TTypeList, typename T>
  inline constexpr bool type_list_contains_v = etl::type_list_contains<TTypeList, T>::value;
#endif
 
  //***************************************************************************
  //***************************************************************************
  template <typename T>
  struct type_list_max_size;
 
  template <typename... TTypes>
  struct type_list_max_size<etl::type_list<TTypes...>>
    : public etl::integral_constant<size_t, etl::largest<TTypes...>::size>
  {
  };
 
  template <>
  struct type_list_max_size<type_list<>>
    : public etl::integral_constant<size_t, 0>
  {
  };
 
#if ETL_USING_CPP17
  template <typename TTypeList>
  inline constexpr size_t type_list_max_size_v = etl::type_list_max_size<TTypeList>::value;
#endif
 
  //***************************************************************************
  //***************************************************************************
  template <typename T>
  struct type_list_max_alignment;
 
  template <typename... TTypes>
  struct type_list_max_alignment<etl::type_list<TTypes...>>
    : public etl::integral_constant<size_t, etl::largest<TTypes...>::alignment>
  {
  };
 
  template <>
  struct type_list_max_alignment<type_list<>>
    : public etl::integral_constant<size_t, 1>
  {
  };
 
#if ETL_USING_CPP17
  template <typename TTypeList>
  inline constexpr size_t type_list_max_alignment_v = etl::type_list_max_alignment<TTypeList>::value;
#endif
 
  //***************************************************************************
  //***************************************************************************
  template <typename TTypeList, size_t... Indices>
  struct type_list_select
  {
    ETL_STATIC_ASSERT((etl::is_base_of<etl::type_list<>, TTypeList>::value), "TTypeList must be an etl::type_list");
 
    using type = type_list<type_list_type_at_index_t<TTypeList, Indices>...>;
  };
 
  template <typename TTypeList, size_t... Indices>
  using type_list_select_t = typename type_list_select<TTypeList, Indices...>::type;
 
  //***************************************************************************
  //***************************************************************************
  template <typename... TTypes>
  struct type_list_cat;
 
  template <typename... TTypes1, typename... TTypes2, typename... TTail>
  struct type_list_cat<etl::type_list<TTypes1...>, etl::type_list<TTypes2...>, TTail...>
  {
    using type = typename type_list_cat<etl::type_list<TTypes1..., TTypes2...>, TTail...>::type;
  };
 
  template <typename T>
  struct type_list_cat<T>
  {
    using type = T;
  };
 
  template <typename... TypeLists>
  using type_list_cat_t = typename type_list_cat<TypeLists...>::type;
 
  //***************************************************************************
  //***************************************************************************
  // Primary template
  template <typename TFromList, typename TToList>
  struct type_lists_are_convertible;
 
  // Specialization: both lists empty, convertible
  template <>
  struct type_lists_are_convertible<etl::type_list<>, etl::type_list<>> 
    : public etl::true_type
  {
  };
 
  // Recursive case: check head types, then recurse
  template <typename TFromHead, typename... TFromTail, typename TToHead, typename... TToTail>
  struct type_lists_are_convertible<etl::type_list<TFromHead, TFromTail...>, etl::type_list<TToHead, TToTail...>> 
    : public etl::bool_constant<etl::is_convertible<TFromHead, TToHead>::value && 
                                etl::type_lists_are_convertible<etl::type_list<TFromTail...>, etl::type_list<TToTail...>>::value>
  {
    static_assert(sizeof...(TFromTail) == sizeof...(TToTail), "Type lists are not the same length");
  };
 
#if ETL_USING_CPP17
  template <typename TFromList, typename TToList>
  inline constexpr bool type_lists_are_convertible_v = etl::type_lists_are_convertible<TFromList, TToList>::value;
#endif
}
#endif
 
#endif