table of contents
std::initializer_list::initializer_list(3) | C++ Standard Libary | std::initializer_list::initializer_list(3) |
NAME¶
std::initializer_list::initializer_list - std::initializer_list::initializer_list
Synopsis¶
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
2022.07.31 | http://cppreference.com |