C++

Reference

<array>

array

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

array::operator[]
Access element (public member function)
array::front
Access first element (public member function)
array::back
Access last element (public member function)