C++ Primer Plus

Using Objects as Exceptions

Typically, functions that throw exceptions throw objects. One important advantage of this is that you can use different exception types to distinguish among different functions and situations that produce exceptions. Also an object can carry information with it, and you can use this information to help identify the conditions that caused the exception to be thrown. Also in principle a catch block could use that information to decide which course of action to pursue. Here, for example, is one possible design for an exception to be thrown by the hmean() function:

class bad_hmean{private:    double v1;    double v2;public:    bad_hmean(int a = 0, int b = 0) : v1(a), v2(b){}    void mesg();};inline void bad_hmean::mesg() ...