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# std::remove_all_extents

From cppreference.com
< cpp‎ | types

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`.

### [edit] Member types

Name | Definition
`type` | the type of the element of `T`

### [edit] Helper types

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

### [edit] 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 Tp, std::size_t N>
    struct remove_all_extents<T[N]> {
        typedef typename remove_all_extents<T>::type type;
    };

### [edit] Example

Run this code

    #include <iostream>
    #include <type_traits>
    #include <typeinfo>

    template<class A>
    void foo(const A&)
    {
        typedef typename std::remove_all_extents<A>::type Type;
        std::cout << "underlying type: " << typeid(Type).name() << '\n';
    }

    int main()
    {
        float a1[1][2][3];
        int a2[3][2];
        float a3[1][1][1][1][2];
        double a4[2][3];

        foo(a1);
        foo(a2);
        foo(a3);
        foo(a4);
    }

Output:

    underlying type: f
    underlying type: i
    underlying type: f
    underlying type: d

### [edit] See also

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

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