std::initializer_list constructors

Default constructor

since C++14

Simplified

initializer_list();

• this constructor is constexpr and noexcept

Detailed

constexpr initializer_list() noexcept;

until C++14

Simplified

initializer_list();

• this constructor is noexcept

Detailed

initializer_list() noexcept;

Constructs an empty initializer list.

note

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

Complexity

Constant - O(1).

Example

#include <initializer_list>
#include <iostream>
#include <vector>

int main() {
  std::initializer_list<int> ilist; // default constructed

  // implicitly construced initializer list
  for(int i : { 1, 2, 3 }) std::cout << i << ' ';

  // list initialization, implicitly constructed initializer list
  std::vector<int> v = { 4, 5, 6, 7, 8 };
  for(int i : v) std::cout << i << ' ';
}

Result

1 2 3 4 5 6 7 8