Exception Handling - Example 8a - Exception Handling classes

// File: eh8a.cpp - Exception Handling classes

#include <<ostream>
#include <string>
using namespace std;

class ZeroDenominator
{
public:
	ZeroDenominator() {}
	friend ostream& operator<<(ostream& out, const ZeroDenominator& error);
};

class fraction
{
	int numer, denom;
public:
	fraction(int n = 0, int d = 1) : numer(n), denom(d)
	{
		cout << "fraction constructor called\n";
		if (denom == 0) throw ZeroDenominator();
	}
	~fraction() { cout << "fraction destructor called\n"; }
	friend ostream& operator<<(ostream& o, const fraction& f)
	{
		return (o << f.numer << '/' << f.denom);
	}
};

class InputError
{
	string stream;
public:
	InputError(string name) : stream(name) {}
	friend ostream& operator<<(ostream& out, const InputError& error);
};


ostream& operator<<(ostream& out, const InputError& error)
{
	out << "Error in " << error.stream << endl;
	return out;
}


ostream& operator<<(ostream& out, const ZeroDenominator& error)
{
	out << "ZeroDenominator Error"  << endl;
	return out;
}

int main()
{
	int i1, i2;
	cout << "Enter two ints => ";

	try {
		cin >> i1 >> i2;
		if (cin.fail()) throw InputError("cin");
		//	You could also use (!cin) instead of (cin.fail())
		//	cin.bad() did not detect error in cin
		fraction f(i1,i2);
		cout << f << endl;	// Should this line be in the try block?
	}
	catch (const InputError& error) {
		cerr << error << endl;
	}
	catch (const ZeroDenominator& errmsg) {
		cerr << errmsg << endl;
	}
	catch (...) {
		cerr << "help\n";
	}

	cout << "*** End of Program ***\n";
	return 0;
}

***** Compilation and Execution using gnu 3.4.2 on Windows XP *****

C:\deanza\cis52g\examples\exception_handling>g++ eh8a.cpp -Wall -fexceptions

C:\deanza\cis52g\examples\exception_handling>a
Enter two ints => 3 4
fraction constructor called
3/4
fraction destructor called
*** End of Program ***

C:\deanza\cis52g\examples\exception_handling>a
Enter two ints => 3 0
fraction constructor called
ZeroDenominator Error

*** End of Program ***

C:\deanza\cis52g\examples\exception_handling>a
Enter two ints => one two
Error in cin

*** End of Program ***