Evaluate if integer is POT (Power Of Two) [duplicate]

Question

Possible Duplicates:
Query about working out whether number is a power of 2
How to check if a number is a power of 2

I require a function body for this prototype:

bool isPOT(int x);

So it would return eg isPOT(3) = FALSE, but isPOT(8) = TRUE

What is the most pretty/concise algorithm? And what is the most efficient?

PS: I am amazed that I cannot find this question on SO, so I am fully expecting someone to detect some duplicate.

PPS: can someone please create POT, NPOT, Power-Of-Two tags?

Answer 1

bool IsPOT(int x)
{
    return (x > 0) && ((x & (x - 1)) == 0);
}

Answer 2

Not sure if this exact question occurred, but the check is easy

x & (x - 1) == 0