std::remove_extent

 

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

If T is an array of some type X, provides the member typedef type equal to X, otherwise type is T. Note that if T is a multidimensional array, only the first dimension is removed.

If the program adds specializations for std::remove_extent, the behavior is undefined.

Member types

Name	Definition
type	the type of the element of T

Helper types

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

Possible implementation

template<class T> struct remove_extent { using type = T; };   template<class T> struct remove_extent<T[]> { using type = T; };   template<class T, std::size_t N> struct remove_extent<T[N]> { using type = T; };

Example

Run this code

#include <algorithm>
#include <iostream>
#include <iterator>
#include <type_traits>
 
template<class A>
    std::enable_if_t<std::rank_v<A> == 1>
print_1d(const A& a)
{
    std::copy(a, a + std::extent_v<A>,
        std::ostream_iterator<std::remove_extent_t<A>>(std::cout, " "));
    std::cout << '\n';
}
 
int main()
{
    int a[][3] = {{1, 2, 3}, {4, 5, 6}};
//  print_1d(a); // compile-time error
    print_1d(a[1]);
}

Output:

4 5 6

See also

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