Is there a way to deduce a type of a single element of an array in c++

Question

I'm having problem with deducing a type of a single element of an c++ array.

I would like to do achieve something like:

template <class T>
struct array_element { };

template <class T>
struct array_element<T[]> {
   using type = T;
};

int main() {
   int a[5] = {1, 2, 3, 4, 5};
   array_element<decltype(a)>::type element = a[0];
}

But the code obviously does not compile (the int[5] does not match T[])...

Answer 1

You need an extra argument for the specialization:

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

---

Alternatively:

std::remove_reference<decltype(a[0])>::type element = a[0];

Or:

auto element = a[0];

Answer 2

Use std::remove_extent template class (C++11) or std::remove_extent_t alias template (C++14) to get a type of an array element (both are declared in type_traits header file):

std::remove_extent<decltype(a)>::type element0 = a[0];

std::remove_extent_t<decltype(a)> element1 = a[1];

Live demo

You can also use std::remove_all_extents (C++11) or std::remove_all_extents_t (C++14) to get a type of an element of a multidimensional array.