17 Language support library [support]

17.10 Initializer lists [support.initlist]

17.10.1 General [support.initlist.general]

The header <initializer_­list> defines a class template and several support functions related to list-initialization (see [dcl.init.list]).
All functions specified in [support.initlist] are signal-safe ([support.signal]).

17.10.2 Header <initializer_­list> synopsis [initializer.list.syn]

// all freestanding namespace std { template<class E> class initializer_list { public: using value_type = E; using reference = const E&; using const_reference = const E&; using size_type = size_t; using iterator = const E*; using const_iterator = const E*; constexpr initializer_list() noexcept; constexpr size_t size() const noexcept; // number of elements constexpr const E* begin() const noexcept; // first element constexpr const E* end() const noexcept; // one past the last element }; // [support.initlist.range], initializer list range access template<class E> constexpr const E* begin(initializer_list<E> il) noexcept; template<class E> constexpr const E* end(initializer_list<E> il) noexcept; }
An object of type initializer_­list<E> provides access to an array of objects of type const E.
[Note 1:
A pair of pointers or a pointer plus a length would be obvious representations for initializer_­list.
initializer_­list is used to implement initializer lists as specified in [dcl.init.list].
Copying an initializer list does not copy the underlying elements.
— end note]
If an explicit specialization or partial specialization of initializer_­list is declared, the program is ill-formed.

17.10.3 Initializer list constructors [support.initlist.cons]

constexpr initializer_list() noexcept;
Postconditions: size() == 0.

17.10.4 Initializer list access [support.initlist.access]

constexpr const E* begin() const noexcept;
Returns: A pointer to the beginning of the array.
If size() == 0 the values of begin() and end() are unspecified but they shall be identical.
constexpr const E* end() const noexcept;
Returns: begin() + size().
constexpr size_t size() const noexcept;
Returns: The number of elements in the array.
Complexity: Constant time.

17.10.5 Initializer list range access [support.initlist.range]

template<class E> constexpr const E* begin(initializer_list<E> il) noexcept;
Returns: il.begin().
template<class E> constexpr const E* end(initializer_list<E> il) noexcept;
Returns: il.end().