I don't see why one would want to use another negative number here. Not saying that a constant is bad, but it does not seem to add much either. I was wondering what the best practice could be. In Java, we have functions that use constant -1 as part of their public contract, e.g., http://docs.oracle.com/javase/7/docs/api/java/lang/String.html#indexOf%28int%29 If it is not a problem there, why should we worry about it here?