initializer_list(); | (since C++11) (until C++14) | |
constexpr initializer_list(); | (since C++14) |
Constructs an empty initializer list.
Parameters
(none).
Exceptions
noexcept specification: noexceptComplexity
Constant.
Example
#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
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