Make const member functions thread safe unless we’re certain they’ll never be used in a concurrent context.

constexpr objects are const and are initialized with values known during compilation; constexpr functions can produce copmile-time results when called with arguments whose values are know during compilations.

Most functions are exception-neutral, but for some, such as move operations, swap, memory deallocation functions, and destructors, noexcept is particularly valuable.

In maximally generic code, prefer non-member versions of begin, end, rbegin, etc., over their member function counterparts.

C++11 gives us a way to make explicit that a derived class function is supposed to override a base class version: override.