Range-based for loops can be used in various ways:

• By committing to a specific type for the elements of the sequence:

        auto rates = getRates();
        for (int rate : rates) 
          std::cout << rate << std::endl; 
        for (int& rate : rates) 
          rate *= 2;

• By not specifying a type and letting the compiler deduce it:

        for (auto&& rate : getRates()) 
          std::cout << rate << std::endl; 

        for (auto & rate : rates) 
          rate *= 2; 

        for (auto const & rate : rates) 
          std::cout << rate << std::endl;

• By using structured bindings and decomposition declaration in C++17:

        for (auto&& [rate, flag] : getRates2()) 
          std::cout << rate << std::endl;