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.