std::initializer_list<T>:: initializer_list

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

#include <initializer_list>
#include <iostream>
 
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');
}

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