std::underlying_type – cppreference.com

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definiert in Header `<type_traits>`

`template< class T > struct underlying_type;`		(seit C++11)

Legt ein Mitglied typedef type der Typ, der zugrunde liegende Typ für die Zählung T ist .

Original:

Defines a member typedef type of type that is the underlying type for the enumeration T.

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Mitglied Typen


Name Original: Name The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.	Definition

`type`	der zugrunde liegende Typ für `T` Original: the underlying type for `T` The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

Notes

Jeder Aufzählungstyp hat einen zugrunde liegenden Typ, der sein kann

Original:

Each enumeration type has an underlying type, which can be

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Ein. Explizit (beide scoped und ohne Bereichseinschränkung Aufzählungen) angegeben

Original:

1. Specified explicitly (both scoped and unscoped enumerations)

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2. Weggelassen wird, in welchem Fall es int ist für scoped Aufzählungen oder eine Implementierung definiert integraler Typ, der stellvertretend für alle Werte der Enum (für ohne Bereichseinschränkung Aufzählungen)

Original:

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)

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Beispiel

#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