1.3.2 Braced Initializer

• In C++03, aggregate types (arrays and structs with no constructor) could be initialized with braced initializer lists.
  struct Point { int x; int y; }; 
  Point p = {1, 2};
• In C++11, this syntax was generalized, and any object type can now be created with a braced initializer list, known as a braced-init-list in the C++ grammar.
  vector<string> v = {"foo", "bar"}; 
   
  auto p = new vector<string>{"foo", "bar"}; 
   
  //map defined by a list of pairs. Nested braced-init-lists work. 
  map<int, string> m = {{1, "one"}, {2, "2"}}; 
   
  //braced-init-list can be implicitly converted to a return type. 
  vector<int> test_function() { return {1, 2, 3}; } 
   
  // Iterate over a braced-init-list. 
  for (int i : {-1, -2, -3}) {} 
   
  // Call a function using a braced-init-list. 
  void TestFunction2(std::initializer_list<int> init_list) {} 
  TestFunction2({1, 2, 3});
• When use with auto, you need to be careful
  auto d = {1.23}; 
  // d is a std::initializer_list<double> 
  auto d = double{1.23}; 
  // Good -- d is a double, not a std::initializer_list.