initializer_list() noexcept; | (since C++11) (until C++14) | |
constexpr initializer_list() noexcept; | (since C++14) |
Constructs an empty initializer list.
(none).
Constant.
Despite a lack of constructors, it is possible to create non-empty initializer lists. Instances of std::initializer_list
are implicitly constructed when:
auto
, including in a ranged for loop #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
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