In my quest to count the bits in an integer's binary representation using recursion, I encountered a unexpected outcome due to operator precedence:

Working Code:

int f(int n) {
    return (n ? (n & 1) + f(n >> 1) : 0);
}

Not Working Code:

int f(int n) {
    return (n ? n & 1 + f(n >> 1) : 0);
}

The big difference? Operator rules. In the first code, it works because we use parentheses to make sure the "AND" operation happens first.

In the second code, missing parentheses cause the compiler to interpret it as n & (1 + f(n >> 1)), resulting in an incorrect bit count.

To avoid confusion and errors, always use parentheses to clarify your intended order of operations in programming.

Additionally, it's important to note that in C++ and many other programming languages, the plus (+) and minus (-) operators have higher precedence than the bitwise AND (&) and OR (|) operators. To understand the complete operator precedence hierarchy, you can refer to resources such as cppreference.com's operator precedence page.