public member function

std::array::at

<array> 
      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 or equal than 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 vector 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

Element n is potentially accessed or modified by the caller. Concurrently accessing or modifying other 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 )

C++