std::array<T,N>::front
Min standard notice:
Returns a reference to the first element in the container.
# Declarations
reference front();
(since C++11) (constexpr since C++17)
const_reference front() const;
(since C++11) (constexpr since C++14)
# Return value
Reference to the first element.
# Notes
For a container c, the expression c.front() is equivalent to *c.begin().
# Example
#include <cassert>
#include <array>
int main()
{
std::array<char, 4> letters{'a', 'b', 'c', 'd'};
assert(letters.front() == 'a');
}