STL get<IDX|TYPE>(OBJ) and set<IDX|TYPE>(OBJ,VAL) in C++

Several STL global functions grant access by index or, since C++14, by type, for (array, span, pair, tuple, variant within their (static) sizes.):

• tuples:

  auto t = std::make_tuple(1, "Foo", 3.14);
  std::cout << "( " << get<0>(t); // access by index
  std::cout << "( " << get<int>(t); // access by type

• variants:

  std::variant<int, float> v{12}, w;
  std::cout << std::get<int>(v) < '\n';

• pairs:

  std::pair <int,char> foo (10,'x');
  std::get<0>(foo) = 50;