return n > 0 && n&(n-1) == 0
}
func isPowerOfTwo16(n int16) bool {
	return n > 0 && n&(n-1) == 0
}
func isPowerOfTwo32(n int32) bool {
	return n > 0 && n&(n-1) == 0
}
func isPowerOfTwo64(n int64) bool {
	return n > 0 && n&(n-1) == 0
}

// isUint64PowerOfTwo reports whether uint64(n) is a power of 2.
func isUint64PowerOfTwo(in int64) bool {
	n := uint64(in)
	return n > 0 && n&(n-1) == 0