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std::remove_all_extents

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

If T is a multidimensional array of some type X, provides the member typedef type equal to X, otherwise type is T.

The behavior of a program that adds specializations for std::remove_all_extents is undefined.

Member types

Name Definition
type the type of the element of T

Helper types

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

Possible implementation

template<class T>
struct remove_all_extents { typedef T type; };
 
template<class T>
struct remove_all_extents<T[]> {
    typedef typename remove_all_extents<T>::type type;
};
 
template<class T, std::size_t N>
struct remove_all_extents<T[N]> {
    typedef typename remove_all_extents<T>::type type;
};

Example

#include <iostream>
#include <type_traits>
#include <typeinfo>
 
template<class A>
void info(const A&)
{
    typedef typename std::remove_all_extents<A>::type Type;
    std::cout << "underlying type: " << typeid(Type).name() << '\n';
}
 
int main()
{
    float a0;
    float a1[1][2][3];
    float a2[1][1][1][1][2];
    float* a3;
    int a4[3][2];
    double a5[2][3];
    struct X { int m; } x0[3][3];
 
    info(a0);
    info(a1);
    info(a2);
    info(a3);
    info(a4);
    info(a5);
    info(x0);
}

Possible output:

underlying type: float
underlying type: float
underlying type: float
underlying type: float*
underlying type: int
underlying type: double
underlying type: main::X

See also

(C++11)
checks if a type is an array type
(class template)
(C++11)
obtains the number of dimensions of an array type
(class template)
(C++11)
obtains the size of an array type along a specified dimension
(class template)
(C++11)
removes one extent from the given array type
(class template)

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