std::array::front

      reference front();const_reference front() const;

Access first element

Returns a reference to the first element in the array container.

Unlike member array::begin, which returns an iterator to this same element, this function returns a direct reference.

Calling this function on an empty container causes undefined behavior.

Parameters

none

Return value

A reference to the first element in the array.

If the array object is const-qualified, the function returns a

const_reference. Otherwise, it returns a reference.

Member types

reference and const_reference are the reference types to the elements of the array (see array member types).

Example

// array::front
#include <iostream>
#include <array>

int main ()
{
  std::array<int,3> myarray = {2, 16, 77};

  std::cout << "front is: " << myarray.front() << std::endl;   // 2
  std::cout << "back is: " << myarray.back() << std::endl;     // 77

  myarray.front() = 100;

  std::cout << "myarray now contains:";
  for ( int& x : myarray ) std::cout << ' ' << x;

  std::cout << '\n';

  return 0;
}

Output:

front is: 2
back is: 77
myarray now contains: 100 16 77

Complexity

Constant.

Iterator validity

No changes.

Data races

The reference returned can be used to access or modify elements. Concurrently accessing or modifying different elements is safe.

Exception safety

If the container is not empty, the function never throws exceptions (no-throw guarantee).
Otherwise, it causes undefined behavior.