std::conditional
From Cppreference
| Defined in header <type_traits>
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| template< bool B, class T, class F >
struct conditional; |
(C++11 feature) | |
Provides member typedef type, which is defined as T if B is true at compile time, or as F if B is false.
Contents |
[edit] Member types
| Member type | Definition |
| type | T if B == true, F if B == false |
[edit] Equivalent definition
template<bool B, class T, class F> struct conditional { typedef T type; }; template<class T, class F> struct conditional<false, T, F> { typedef F type; }; |
[edit] Example
#include <iostream> #include <type_traits> #include <typeinfo> int main() { typedef std::conditional<true, int, double>::type Type1; typedef std::conditional<false, int, double>::type Type2; typedef std::conditional<sizeof(int) >= sizeof(double), int, double>::type Type3; std::cout << typeid(Type1).name() << '\n'; std::cout << typeid(Type2).name() << '\n'; std::cout << typeid(Type3).name() << '\n'; }
Output:
i d d
[edit] See also
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hides a function overload or template specialization based on compile-time boolean (class template) |
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