std::add_pointer
Defined in header <type_traits> | | |
|---|---|---|
template< class T > struct add_pointer; | | (since C++11) |
如果T是一个引用类型，然后提供成员类型type它是指向引用类型的指针。
否则，如果T为对象类型命名，则不属于cv或ref限定%28的函数类型(因为C++17%29)或%28(可能是cv限定%29空类型)提供了type哪种类型T*...
Otherwise (if T is a cv- or ref-qualified function type), provides the member typedef type which is the type T. | (since C++17) |
|---|
成员类型
Name | Definition |
|---|---|
type | pointer to T or to the type referenced by T |
帮助者类型
template< class T > using add_pointer_t = typename add_pointer<T>::type; | | (since C++14) |
|---|
可能的实施
命名空间详细信息{Template<class T，bool是[医]功能[医]type=false>structadd[医]指针{使用type=type Name std：：Remove[医]参照系<T>*类型%2A模板<class T>结构添加[医]指针<T，true>{使用type=T；}；模板<类T，类...。args>structadd[医]指针<T%28 Args...%29，true>{使用类型=T%28%2A%29%28 Args...%29；}；模板<T类，类...。args>structadd[医]指针<T%28 Args...，...%29，true>{使用类型=T%28%2A%29%28 Args...，...%29；}；}/命名空间详细模板<class T>结构添加[医]指针：详细信息：：添加[医]指针<T，std：：is[医]功能<T>*价值>{}；
*。
例
二次
#include <iostream>
#include <type_traits>
int main()
{
int i = 123;
int& ri = i;
typedef std::add_pointer<decltype(i)>::type IntPtr;
typedef std::add_pointer<decltype(ri)>::type IntPtr2;
IntPtr pi = &i;
std::cout << "i = " << i << "\n";
std::cout << "*pi = " << *pi << "\n";
static_assert(std::is_pointer<IntPtr>::value, "IntPtr should be a pointer");
static_assert(std::is_same<IntPtr, int*>::value, "IntPtr should be a pointer to int");
static_assert(std::is_same<IntPtr2, IntPtr>::value, "IntPtr2 should be equal to IntPtr");
typedef std::remove_pointer<IntPtr>::type IntAgain;
IntAgain j = i;
std::cout << "j = " << j << "\n";
static_assert(!std::is_pointer<IntAgain>::value, "IntAgain should not be a pointer");
static_assert(std::is_same<IntAgain, int>::value, "IntAgain should be equal to int");
}二次
产出：
二次
i = 123
*pi = 123
j = 123二次
另见
is_pointer (C++11) | checks if a type is a pointer type (class template) |
|---|---|
remove_pointer (C++11) | removes pointer from the given type (class template) |
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