array at() function in C++ STL (original) (raw)

Last Updated : 13 Jun, 2022

The array::at() is a built-in function in C++ STL which returns a reference to the element present at location i in given array. Syntax:

array_name.at(i)

Parameters: The function accepts a single mandatory parameter i which specifies the location. Return value: The function returns an element present at index i in given array if i is valid index otherwise it throws out_of_range exception. Time Complexity: O(1) Below programs demonstrate the array::at() function: Program 1:

CPP `

// CPP program to illustrate // the array::at() function #include <bits/stdc++.h> using namespace std;

int main() { // array initialisation array<int, 5> arr = { 1, 5, 2, 4, 7 };

// prints the element at ith index
// index starts from zero
cout << "The element at index 2 is " << arr.at(2) << endl;

return 0;

}

`

Output:

The element at index 2 is 2

Program 2 : Illustrating function when it is implemented on lesser size array causing an error.

CPP `

// CPP program to illustrate // the array::at() function #include <bits/stdc++.h> using namespace std;

int main() { // array initialisation array<int, 5> arr = { 1, 5, 2, 4, 7 };

// it is an exception
cout << "The element at index 7 is " << arr.at(7) << endl;

return 0;

}

`

Output:

Abort signal from abort(3) (SIGABRT)

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