Why Does `==` Not Work for Array Equality Comparison in C ?

Why does array equality comparison using == not work?

In C , the equality operator (==) compares the memory addresses of arrays, rather than their contents. This behavior can lead to confusion, as it differs from the intuitive expectation of comparing array elements element-wise.

Consider the following code:

int main()
{
    int iar1[] = {1, 2, 3, 4, 5};
    int iar2[] = {1, 2, 3, 4, 5};

    if (iar1 == iar2)
        cout << "Arrays are equal.";
    else
        cout << "Arrays are not equal.";
}

In this code, two arrays are created with identical contents. However, the output states that the arrays are not equal. This is because the == operator compares the memory addresses of the arrays, which are different for each array.

To perform element-wise comparison of arrays, one can either use a loop or utilize the std::array class. The std::array class provides a slightly different interface for working with arrays and supports direct equality comparison.

Example using a loop:

bool arraysEqual(int *arr1, int *arr2, int size)
{
    for (int i = 0; i < size; ++i)
    {
        if (arr1[i] != arr2[i])
            return false;
    }
    return true;
}

Example using std::array:

#include <array>

int main()
{
    std::array<int, 5> iar1 = {1, 2, 3, 4, 5};
    std::array<int, 5> iar2 = {1, 2, 3, 4, 5};

    if (iar1 == iar2)
        cout << "Arrays are equal.";
    else
        cout << "Arrays are not equal.";
}

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