C++

Reference

<array>

array

public member function
<array>

std::array::operator[]

      reference operator[] (size_type n);const_reference operator[] (size_type n) const;
Access element
Returns a reference to the element at position n in the array container.

A similar member function, array::at, has the same behavior as this operator function, except that array::at checks the array bounds and signals whether n is out of range by throwing an exception.

Parameters

n
Position of an element in the array.
Notice that the first element has a position of 0, not 1.
Member type size_type is an alias of the unsigned integral type size_t.

Return value

The element at the specified position 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

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// array::operator[]
#include <iostream>
#include <array>

int main ()
{
  std::array<int,10> myarray;
  unsigned int i;

  // assign some values:
  for (i=0; i<10; i++) myarray[i]=i;

  // print content
  std::cout << "myarray contains:";
  for (i=0; i<10; i++)
    std::cout << ' ' << myarray[i];
  std::cout << '\n';

  return 0;
}

Output:
myarray contains: 0 1 2 3 4 5 6 7 8 9


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 size is greater than n, the function never throws exceptions (no-throw guarantee).
Otherwise, it causes undefined behavior.

See also

array::at
Access element (public member function)
array::front
Access first element (public member function)
array::back
Access last element (public member function)