template usage

templatearray.cc

// return size of an array as a compile-time constant. (The
// array parameter has no name, because we care only about
// the number of elements it contains.)
template<typename T, std::size_t N>                 // see info
constexpr std::size_t arraySize(T (&)[N]) noexcept  // below on
{                                                   // constexpr
    return N;                                         // and
}

template<typename Container, typename Index>       // final
decltype(auto)                                     // C++14
authAndAccess(Container&& c, Index i)              // version
{
  authenticateUser();
  return std::forward<Container>(c)[i];
}

std::deque<int> d;
authAndAccess(d, 5) = 10;