The header <initializer_list> defines a class template and several support functions related to list-initialization (see [dcl.init.list]).
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: 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.
constexpr initializer_list() noexcept;
Effects: constructs an empty initializer_list object.
Postconditions: size() == 0
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.
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().