C++ Type Traits Type Properties
Example
C++11
Type properties compare the modifiers that can be placed upon different variables. The usefulness of these type traits is not always obvious.
Note: The example below would only offer an improvement on a non-optimizing compiler. It is a simple a proof of concept, rather than complex example.
e.g. Fast divide by four.
template<typename T>
inline T FastDivideByFour(cont T &var) {
// Will give an error if the inputted type is not an unsigned integral type.
static_assert(std::is_unsigned<T>::value && std::is_integral<T>::value,
"This function is only designed for unsigned integral types.");
return (var >> 2);
}
Is Constant:
This will evaluate as true when type is constant.
std::cout << std::is_const<const int>::value << "\n"; // Prints true.
std::cout << std::is_const<int>::value << "\n"; // Prints false.
Is Volatile:
This will evaluate as true when the type is volatile.
std::cout << std::is_volatile<static volatile int>::value << "\n"; // Prints true.
std::cout << std::is_const<const int>::value << "\n"; // Prints false.
Is signed:
This will evaluate as true for all signed types.
std::cout << std::is_signed<int>::value << "\n"; // Prints true.
std::cout << std::is_signed<float>::value << "\n"; // Prints true.
std::cout << std::is_signed<unsigned int>::value << "\n"; // Prints false.
std::cout << std::is_signed<uint8_t>::value << "\n"; // Prints false.
Is Unsigned:
Will evaluate as true for all unsigned types.
std::cout << std::is_unsigned<unsigned int>::value << "\n"; // Prints true.
std::cout << std::is_signed<uint8_t>::value << "\n"; // Prints true.
std::cout << std::is_unsigned<int>::value << "\n"; // Prints false.
std::cout << std::is_signed<float>::value << "\n"; // Prints false.
