std::underlying_type
From cppreference.com
Defined in header
<type_traits>
|
||
template< class T >
struct underlying_type; |
(since C++11) | |
Defines a member typedef type
of type that is the underlying type for the complete (since C++17) enumeration type T
.
Contents |
[edit] Member types
Name | Definition |
type
|
the underlying type for T
|
[edit] Helper types
template< class T >
using underlying_type_t = typename underlying_type<T>::type; |
(since C++14) | |
[edit] Notes
Each enumeration type has an underlying type, which can be
1. Specified explicitly (both scoped and unscoped enumerations)
2. Omitted, in which case it is int for scoped enumerations or an implementation-defined integral type capable of representing all values of the enum (for unscoped enumerations)
[edit] Example
Run this code
#include <iostream> #include <type_traits> enum e1 {}; enum class e2: int {}; int main() { bool e1_type = std::is_same< unsigned ,typename std::underlying_type<e1>::type >::value; bool e2_type = std::is_same< int ,typename std::underlying_type<e2>::type >::value; std::cout << "underlying type for 'e1' is " << (e1_type?"unsigned":"non-unsigned") << '\n' << "underlying type for 'e2' is " << (e2_type?"int":"non-int") << '\n'; }
Output:
underlying type for 'e1' is unsigned underlying type for 'e2' is int