What about if cSalary's operator() creates a temporary object? That temporary object could throw. That's technically two throws. But of course you could extend this reasoning forever. I guess you have to consider their Assumption b). Anyway, calling e.Salary() results in one additional execution path from the standpoint of the function and it can be either: - a member function that simply throws OR - a member function that creates a temporary whose construction could throw OR - an overloaded operator() on a member variable that throws Fun little exercise though. Regards, Jeff