Switch Case语句中的C ++循环

Question

How do I loop this switch case? I need to be able to loop back to the menu selection after after each switch case to make a new selection. Help?

int _tmain(int argc, _TCHAR* argv[]){

    char choice;
    showWelcome();  // Show Welcom Screen
    showMenu();     // Show Menu Screen
    cin >> choice;  // Make Menu Secection
    {
            switch(choice)
            {
            case'1':
                seriesCalc();
                break;

            case'2':
                parallelCalc();
                break;

            case'q':
                system("cls");
                break;

            default:
                break;
                return 0;
            }

    }       

} // end main

Answer 1

while(cin){ 
    cin >> choice;  // Make Menu Secection
    {
            switch(choice)
            {
            case'1':
                seriesCalc();
                break;

            case'2':
                parallelCalc();
                break;

            case'q':
                system("cls");
                break;

            default:
                break;
                return 0;
            }

    }       
}

Also if you do not mind the goto statement:

back: cin >> choice;  // Make Menu Secection
{
switch(choice)
{
case'1':
    seriesCalc();
    break;
case'2':
    parallelCalc();
    break;
case'q':
    system("cls");
    break;
default:
    break;
    return 0;
}
goto back;
}

However if you plan on going the goto way: remember

Answer 2

Use a while loop or a do-while loop. You may want to add the possibility for exit in the switch statement, ie while ( loop ) { and case 'q': loop = false .

This is good because it doesn't automatically quit the program afterwards.

Answer 3

int _tmain(int argc, _TCHAR* argv[]){

    char choice;boolean again=true;
    showWelcome();  // Show Welcom Screen
    showMenu();   
while(again){  // Show Menu Screen
    cin >> choice;  // Make Menu Secection
    {
            switch(choice)
            {
            case'1':
                seriesCalc();
                break;

            case'2':
                parallelCalc();
                break;

            case'q':
                system("cls");
                break;

            default:
                again=false;
            }

    }  
return 0; 
}    

} 

Answer 4

int _tmain(int argc, _TCHAR* argv[]){

char choice;
showWelcome();  // Show Welcom Screen
showMenu();     // Show Menu Screen
**while**(cin >> choice)  // Make Menu Secection
{
        switch(choice)
        {
        case'1':
            seriesCalc();
            break;

        case'2':
            parallelCalc();
            break;

        case'q':
            system("cls");
            break;

        default:
            break;
            return 0;
        }

}       

} // end main

std::cin will return a positive value when the input is valid.

Answer 5

Write a function to encapsulate the real work and call it.

for(;;) {
    cin >> choice;
    if (!cin || do_user_command(choice) == cmd_exit)
        break;
}