std::add_pointer

 

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Defined in header <type_traits>
template< class T > struct add_pointer;		(since C++11)

If T is a reference type, then provides the member typedef type which is a pointer to the referred type.

Otherwise, if T names an object type, a function type that is not cv- or ref-qualified (since C++17), or a (possibly cv-qualified) void type, provides the member typedef type which is the type 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)

Member types

Name	Definition
type	pointer to T or to the type referenced by T

Helper types

template< class T > using add_pointer_t = typename add_pointer<T>::type;		(since C++14)

Possible implementation

namespace detail { template< class T, bool is_function_type = false > struct add_pointer { using type = typename std::remove_reference<T>::type*; };   template< class T > struct add_pointer<T, true> { using type = T; };   template< class T, class... Args > struct add_pointer<T(Args...), true> { using type = T(*)(Args...); };   template< class T, class... Args > struct add_pointer<T(Args..., ...), true> { using type = T(*)(Args..., ...); };   } // namespace detail   template< class T > struct add_pointer : detail::add_pointer<T, std::is_function<T>::value> {};

Example

Run this code

#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");
}

Output:

i = 123
*pi = 123
j = 123

See also

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)