[intseq]

# 21 Metaprogramming library [[meta]](./#meta)

## 21.2 Compile-time integer sequences [intseq]

### [21.2.1](#general) General [[intseq.general]](intseq.general)

[1](#general-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/meta.tex#L21)

The library provides a class template that can represent an integer sequence[.](#general-1.sentence-1)

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[.](#general-1.sentence-2)

[*Note [1](#general-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]](tuple.apply "22.4.6 Calling a function with a tuple of arguments")[.](#general-1.sentence-3)

— *end note*]

### [21.2.2](#intseq) Class template integer_sequence [[intseq.intseq]](intseq.intseq)

[🔗](#lib:integer_sequence)

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

[1](#intseq-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/meta.tex#L43)

*Mandates*: T is an integer type[.](#intseq-1.sentence-1)

### [21.2.3](#make) Alias template make_integer_sequence [[intseq.make]](intseq.make)

[🔗](#lib:make_integer_sequence)

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

[1](#make-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/meta.tex#L56)

*Mandates*: N ≥ 0[.](#make-1.sentence-1)

[2](#make-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/meta.tex#L60)

The alias templatemake_integer_sequence denotes a specialization ofinteger_sequence with N constant template arguments[.](#make-2.sentence-1)

The type make_integer_sequence<T, N> is an alias for the typeinteger_sequence<T, 0, 1, …, N - 1>[.](#make-2.sentence-2)

[*Note [1](#make-note-1)*:

make_integer_sequence<int, 0> is an alias for the typeinteger_sequence<int>[.](#make-2.sentence-3)

— *end note*]