Parameter

Pack

Compile time mapping of index to type and type to index for a template parameter pack.

For C++11 or above

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parameter_pack

template <typename... TTypes>

class parameter_pack

Defines

static constexpr size_t size = sizeof...(TTypes);

template <size_t Index, typename... TTypes>

using parameter_pack_t

= typename etl::parameter_pack<TTypes...>::template type_from_index_t<Index>;

Type from index and type list.

For C++17 or above

template <typename T, typename... TTypes>

inline constexpr size_t parameter_pack_v

= etl::parameter_pack<TTypes...>::template index_of_type<T>::value;

Index from type and type list.

The class contains two nested templates.

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index_of_type

template <typename T>

class index_of_type

For C++17 or above

template <typename T>

static constexpr size_t index_of_type_v = index_of_type<T>::value;

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type_from_index

template <size_t Index>

class type_from_index

template <size_t Index>

using type_from_index_t = typename type_from_index<Index>::type;

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Examples

using Pack = etl::parameter_pack<char, short, int>;

constexpr size_t size = Pack::size; // size == 3

size_t indexChar = Pack::index_of_type_v<char>; // indexChar == 0

size_t indexShort = Pack::index_of_type_v<short>; // indexShort == 1

size_t indexInt = Pack::index_of_type_v<int>; // indexInt == 2

size_t indexLong = Pack::index_of_type_v<long>; // Static assert

// "T is not in parameter pack"

using type0 = typename Pack::type_from_index_t<0>; // type0 = char

using type1 = typename Pack::type_from_index_t<1>; // type1 = short

using type2 = typename Pack::type_from_index_t<2>; // type2 = int

using type3 = typename Pack::type_from_index_t<3>; // Static assert

// "Index out of bounds of parameter pack"

parameter_pack.h