std::initializer_list::initializer_list - cppreference.com (original) (raw)

| initializer_list() noexcept; | | (since C++11) (constexpr since C++14) | | ----------------------------- | | ------------------------------------- |

Constructs an empty initializer list.

[edit] Parameters

(none)

[edit] Complexity

Constant

[edit] 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

[edit] Example

#include #include   int main() { std::initializer_list empty_list; std::cout << "empty_list.size(): " << empty_list.size() << '\n';   // create initializer lists using list-initialization std::initializer_list 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 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