21 Metaprogramming library [meta]

21.2 Compile-time integer sequences [intseq]

21.2.1 General [intseq.general]

21.2.2 Class template integer_sequence [intseq.intseq]

21.2.3 Alias template make_integer_sequence [intseq.make]

21.2.4 Structured binding support [intseq.binding]

21.2.1 General [intseq.general]

The library provides a class template that can represent an integer sequence.

When used as an argument to a function template the template parameter pack defining the sequence can be deduced and used in a pack expansion.

[Note 1:

The index_sequence alias template is provided for the common case of an integer sequence of type size_t; see also [tuple.apply].

— end note]

21.2.2 Class template integer_sequence [intseq.intseq]

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namespace std { template<class T, T... I> struct integer_sequence { using value_type = T; static constexpr size_t size() noexcept { return sizeof...(I); } }; }

Mandates: T is an integer type.

21.2.3 Alias template make_integer_sequence [intseq.make]

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template<class T, T N>
  using make_integer_sequence = integer_sequence<T, see below>;

Mandates: N ≥ 0.

The alias template make_integer_sequence denotes a specialization of integer_sequence with N constant template arguments.

The type make_integer_sequence<T, N> is an alias for the type integer_sequence<T, 0, 1, …, N - 1>.

[Note 1:

make_integer_sequence<int, 0> is an alias for the type integer_sequence<int>.

— end note]

21.2.4 Structured binding support [intseq.binding]

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template<class T, T... Values>
  struct tuple_size<integer_sequence<T, Values...>>
    : integral_constant<size_t, sizeof...(Values)> { };

template<size_t I, class T, T... Values>
  struct tuple_element<I, integer_sequence<T, Values...>> {
    using type = T;
  };
template<size_t I, class T, T... Values>
  struct tuple_element<I, const integer_sequence<T, Values...>> {
    using type = T;
  };

Mandates: I < sizeof...(Values).

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template<size_t I, class T, T... Values>
  constexpr T get(integer_sequence<T, Values...>) noexcept;

Mandates: I < sizeof...(Values).

Returns: Values...[I].