Difference between revisions of "cpp/types/decay"
From cppreference.com
m (indentation) |
m (a bit cleaner, clearer) |
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template <typename T, typename U> | template <typename T, typename U> | ||
struct decay_equiv : | struct decay_equiv : | ||
| − | + | std::is_same<U, typename std::decay<T>::type>::value> | |
| − | + | {}; | |
| − | + | ||
int main() | int main() | ||
Revision as of 22:04, 7 September 2013
| Defined in header <type_traits>
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||
| template< class T > struct decay; |
(since C++11) | |
Applies lvalue-to-rvalue, array-to-pointer, and function-to-pointer implicit conversions to the type T, removes cv-qualifiers, and defines the resulting type as the member typedef type. This is the type conversion applied to all function arguments when passed by value.
Contents |
Member types
| Name | Definition |
type
|
the result of applying the decay type conversions to T
|
Helper types
| template< class T > using decay_t = typename decay<T>::type; |
(since C++14) | |
Possible implementation
template< class T > struct decay { typedef typename std::remove_reference<T>::type U; typedef typename std::conditional< std::is_array<U>::value, typename std::remove_extent<U>::type*, typename std::conditional< std::is_function<U>::value, typename std::add_pointer<U>::type, typename std::remove_cv<U>::type >::type >::type type; }; |
Example
Run this code
#include <iostream> #include <type_traits> template <typename T, typename U> struct decay_equiv : std::is_same<U, typename std::decay<T>::type>::value> {}; int main() { std::cout << std::boolalpha << decay_equiv<int[], int*>::value; }
Output:
true
See also
| implicit conversion | array-to-pointer, function-to-pointer, rvalue-to-lvalue conversions |
