std::initializer_list<T>::initializer_list

initializer_list() noexcept;		(since C++11) (until C++14)
constexpr initializer_list() noexcept;		(since C++14)

Constructs an empty initializer list.

Parameters

(none)

Complexity

Constant

Example

Run this code

#include <iostream>
#include <initializer_list>
 
int main() 
{
    std::initializer_list<int> empty_list;
    std::cout << "empty_list.size(): " << empty_list.size() << '\n';
 
    // create initializer lists using list-initialization
    std::initializer_list<int> digits {1, 2, 3, 4, 5};
    std::cout << "digits.size(): " << digits.size() << '\n';
 
    // special rule for auto means 'fractions' has the
    // type std::initializer_list<double>
    auto fractions = {3.14159, 2.71828};
    std::cout << "fractions.size(): " << fractions.size() << '\n';
}

Output:

empty_list.size(): 0
digits.size(): 5
fractions.size(): 2

Notes

Despite a lack of constructors, it is possible to create non-empty initializer lists. Instances of std::initializer_list are implicitly constructed when:

a braced-init-list is used in list-initialization, including function-call list initialization and assignment expressions (not to be confused with constructor initializer lists)
a braced-init-list is bound to auto, including in a ranged for loop

Language
Standard Library Headers
Freestanding and hosted implementations
Named requirements
Language support library
Concepts library (C++20)
Diagnostics library
Utilities library
Strings library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Filesystem library (C++17)
Technical Specifications

Member functions
initializer_list::initializer_list
Capacity
initializer_list::size
Iterators
initializer_list::begin
initializer_list::end
Non-member functions
std::begin
std::end
std::rbegin (C++14)
std::rend (C++14)