17 Language support library [language.support]

17.10 Initializer lists [support.initlist]

17.10.3 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.