Why does comparing arrays using the == operator in C and C often result in 'not equal'?

Array Equality Comparison Using == Operator

When comparing arrays using the == operator, it's important to understand the distinction between pointer decay and element-wise comparison. By default, arrays in C and C decay to pointers to their first elements. This is called pointer decay.

In the provided code snippet:

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.";

When comparing iar1 and iar2 using ==, both arrays will decay to pointers to their first elements. Since iar1 and iar2 are two separate arrays in memory, these pointers will have different values. Consequently, the comparison will evaluate to false (not equal).

To perform an element-wise comparison of the arrays, one can either write a loop that compares each element individually or use the std::array template from the standard template library (STL). The std::array template provides element-wise comparison functionality.

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

if (iar1 == iar2) {
    // Arrays contents are the same
} else {
    // Arrays contents are not the same
}

In this code snippet, the == operator performs an element-wise comparison of the arrays, and the output will indicate whether the contents of the arrays are equal or not.

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