NAME¶

std::initializer_list::initializer_list - std::initializer_list::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

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

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';

// create constexpr initializer list (since C++14)
static constexpr auto ab = {'a', 'b'};
static_assert(ab.size() == 2 and *ab.begin() == 'a');
}

Output:¶

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