Std::initializer_list::initializer_list (3) Linux Manual Page

std::initializer_list<T>::initializer_list – std::initializer_list<T>::initializer_list

Synopsis

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

std::initializer_list::initializer_list (3) Linux Manual Page