std::decay
From cppreference.com
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 |
[edit] Member types
Name | Definition |
type
|
the result of applying the decay type conversions to T
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[edit] Helper types
template< class T >
using decay_t = typename decay<T>::type; |
(since C++14) | |
[edit] 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; }; |
[edit] Example
Run this code
#include <iostream> #include <type_traits> template <typename T, typename U> struct decay_equiv : std::is_same<typename std::decay<T>::type, U>::type {}; int main() { std::cout << std::boolalpha << decay_equiv<int, int>::value << '\n' << decay_equiv<int&, int>::value << '\n' << decay_equiv<int&&, int>::value << '\n' << decay_equiv<const int&, int>::value << '\n' << decay_equiv<int[2], int*>::value << '\n' << decay_equiv<int(int), int(*)(int)>::value << '\n'; }
Output:
true true true true true true
[edit] See also
implicit conversion | array-to-pointer, function-to-pointer, lvalue-to-rvalue conversions |