std::initializer_list<T>::initializer_list
< cpp | utility | 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