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std::remove_extent

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.

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

Example

#include <iostream>
#include <iterator>
#include <algorithm>
#include <type_traits>
 
template<class A>
typename std::enable_if< std::rank<A>::value == 1 >::type
print_1d(const A& a)
{
    copy(a, a+std::extent<A>::value,
         std::ostream_iterator<typename std::remove_extent<A>::type>(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

(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 all extents from the given array type
(class template)

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