Exceptions in C++ how to get back to "main menu" - c++

Question

Well, I'm studying for an exam so I tried to keep my code as simple as possible, but then something very weird happened: the exercise was to change the following code and, by using exceptions, get back to the main menu.
Here's the code of the question:
void ha_ha_loop()
{
int i, c;
while(1)
{
for(i=0; i < 3; i++)
{
cout << "Ha Ha Ha" << endl;
sleep(3);
} // for
ask_return();
} // while
} // ha_ha_loop
void dollar_loop()
{
int i;
while(1)
{
for(i=0; i < 3; i++)
{
cout << "$$$$$$$$$ " << endl;
sleep(3);
} // for
ask_return();
} /* while */
} // dollar_loop
void mainloop()
{
string answer;
while (1)
{
cout << "Press 1 for Ha Ha Ha." << endl;
cout << "Press 2 for $$$$$$$$." << endl;
cout << "Press 3 for to quit." << endl;
cin >> answer;
switch (answer[0])
{
case '1':
ha_ha_loop();
case '2':
dollar_loop();
case '3':
return;
} // switch
} // while
} // mainloop
And what I did was:
void ask_return() {
char c;
cout << "Return to main menu? y/n:"<<endl;
cin >> c;
if (c=='y') throw 1;
}
void ha_ha_loop()
{
int i, c;
while(1)
{
for(i=0; i < 3; i++)
{
cout << "Ha Ha Ha" << endl;
} // for
ask_return();
} // while
} // ha_ha_loop
void dollar_loop()
{
int i;
while(1)
{
for(i=0; i < 3; i++)
{
cout << "$$$$$$$$$ " << endl;
} // for
ask_return();
} /* while */
} // dollar_loop
void mainloop()
{
char answer;
while (1)
{
cout << "Press 1 for Ha Ha Ha." << endl;
cout << "Press 2 for $$$$$$$$." << endl;
cout << "Press 3 for to quit." << endl;
cin >> answer;
switch (answer)
{
case '1':
ha_ha_loop();
case '2':
dollar_loop();
case '3':
return;
}
}
}
int main() {
try {
mainloop();
} catch (...) {
mainloop();
}
}
It works fine at the beginning, but then after one time it terminates my program with an unhandled exception message. Why?
What is the simplest correct way to do that?
Edit:
this is a working way :
void ask_return() {
char c;
cout << "Return to main menu? y/n:"<<endl;
cin >> c;
if (c=='y') throw 1;
}
void ha_ha_loop()
{
int i, c;
while(1)
{
for(i=0; i < 3; i++)
{
cout << "Ha Ha Ha" << endl;
} // for
ask_return();
} // while
} // ha_ha_loop
void dollar_loop()
{
int i;
while(1)
{
for(i=0; i < 3; i++)
{
cout << "$$$$$$$$$ " << endl;
} // for
ask_return();
} /* while */
} // dollar_loop
void mainloop()
{
char answer;
while (1)
{
try {
cout << "Press 1 for Ha Ha Ha." << endl;
cout << "Press 2 for $$$$$$$$." << endl;
cout << "Press 3 for to quit." << endl;
cin >> answer;
switch (answer)
{
case '1':
ha_ha_loop();
case '2':
dollar_loop();
case '3':
return;
}
} catch (...) {
}
}
}
int main() {
mainloop();
}

Answer 1

I'll only answer the "how come" part, since the simplest correct way is what you're supposed to solve yourself. When you do
try {
mainloop();
} catch (...) {
mainloop();
}
you execute mainloop, catching any exceptions. When an exception is caught, the handler executes mainloop again, outside of a try block. You'll want to repeatedly go into mainloop, catching the exception every time.

Answer 2

OK, here's my suggestion.
First, ask_return() needs to get written. This is simple enough, and as far as I can tell you had it more-or-less right. I'm going to suggest actually using a std::exception though:
void ask_return()
{
char c;
cout << "Return to main menu? y/n" << endl;
cin >> c;
if ( c == 'y' )
{
throw std::exception(); // might as well use the class designed for this
}
}
There are numerous places where you could catch the exception, but the easiest place is within mainloop():
void mainloop()
{
string answer;
while (1)
{
cout << "Press 1 for Ha Ha Ha." << endl;
cout << "Press 2 for $$$$$$$$." << endl;
cout << "Press 3 for to quit." << endl;
cin >> answer;
try
{
switch (answer[0])
{
case '1':
ha_ha_loop();
case '2':
dollar_loop();
case '3':
return;
} // switch
}
catch (std::exception& e)
{
// do nothing, let the loop re-run.
}
} // while
} // mainloop
In this case, you don't even need to do anything about the exception: you just let the function keep looping, and it will work.