public member function
<array>

std::array::at

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

The function automatically checks whether n is within the bounds of valid elements in the container, throwing an out_of_range exception if it is not (i.e., if n is greater than, or equal to, its size). This is in contrast with member operator[], that does not check against bounds.

Parameters

n
Position of an element in the array.
If this is greater than, or equal to, the array size, an exception of type out_of_range is thrown.
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::at
#include <iostream>
#include <array>

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

  // assign some values:
  for (int i=0; i<10; i++) myarray.at(i) = i+1;

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

  return 0;
}


Output:
myarray contains: 1 2 3 4 5 6 7 8 9 10

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

Strong guarantee: if an exception is thrown, there are no changes in the container.
It throws out_of_range if n is out of bounds.

See also

  • 9316991614 2018-02-25
  • 191841613 2018-02-25
  • 16411612 2018-02-25
  • 6081981611 2018-02-25
  • 1784561610 2018-02-25
  • 4651609 2018-02-25
  • 9348111608 2018-02-25
  • 2513771607 2018-02-25
  • 6478461606 2018-02-24
  • 4985791605 2018-02-24
  • 5637141604 2018-02-24
  • 282181603 2018-02-24
  • 6217941602 2018-02-24
  • 5076141601 2018-02-24
  • 714281600 2018-02-24
  • 6607141599 2018-02-24
  • 949041598 2018-02-24
  • 6809961597 2018-02-24
  • 671871596 2018-02-24
  • 7107821595 2018-02-24