std::to_underlying - cppreference.com (original) (raw)

Converts an enumeration to its underlying type. Equivalent to return static_cast<std::underlying_type_t<Enum>>(e);.

[edit] Parameters

[edit] Return value

The integer value of the underlying type of Enum, converted from e.

[edit] Notes

std::to_underlying can be used to avoid converting an enumeration to an integer type other than its underlying type.

[edit] Example

#include #include #include #include #include   enum class E1 : char { e }; static_assert(std::is_same_v<char, decltype(std::to_underlying(E1::e))>);   enum struct E2 : long { e }; static_assert(std::is_same_v<long, decltype(std::to_underlying(E2::e))>);   enum E3 : unsigned { e }; static_assert(std::is_same_v<unsigned, decltype(std::to_underlying(e))>);   int main() { enum class ColorMask : std::uint32_t { red = 0xFF, green = (red << 8), blue = (green << 8), alpha = (blue << 8) };   std::cout << std::hex << std::uppercase << std::setfill('0') << std::setw(8) << std::to_underlying(ColorMask::red) << '\n' << std::setw(8) << std::to_underlying(ColorMask::green) << '\n' << std::setw(8) << std::to_underlying(ColorMask::blue) << '\n' << std::setw(8) << std::to_underlying(ColorMask::alpha) << '\n';   // std::underlying_type_t x = ColorMask::alpha; // Error: no known conversion [[maybe_unused]] std::underlying_type_t y = std::to_underlying(ColorMask::alpha); // OK }

Output:

000000FF 0000FF00 00FF0000 FF000000

[edit] See also

| | obtains the underlying integer type for a given enumeration type (class template) [edit] | | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | | checks if a type is an enumeration type (class template) [edit] | | | checks if a type is a scoped enumeration type (class template) [edit] |