std::remove_extent(3)

NAME
std::remove_extent - std::remove_extent

Synopsis
   Defined in header <type_traits>
   template< class T > (since C++11)
   struct remove_extent;
   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 > (since C++14)
   using remove_extent_t = typename remove_extent<T>::type;

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