How to go back to a certain point in the code - c++

Question

I'm new to C++ programming.
I just want to know if there is any way to go back to a certain point in the code without using a while or a do-while loop.
Here is an example:
int a;
cout << "What's 2+2?";
cin >> a;
if (a==4) {cout << "Nice!";}
else {cout << "WRONG! Try again!";}
So, if the player fails, I want to ask the question again, so going back to:
cout << "What's 2+2?";
Is there any way to do it without using a loop?

Answer 1

You want to repeat something until a condition is satisfied. That is the definition of a loop, and there are many ways to write loops in C++. The example you showed is best handled using a do-while loop:
int a;
do
{
cout << "What's 2+2?";
cin >> a;
if (a == 4) {
cout << "Nice!";
break;
}
cout << "WRONG! Try again!";
}
while (true);
Though you could use a while or for loop instead:
int a;
while (true)
{
cout << "What's 2+2?";
cin >> a;
if (a == 4) {
cout << "Nice!";
break;
}
cout << "WRONG! Try again!";
}
int a;
for(;;)
{
cout << "What's 2+2?";
cin >> a;
if (a == 4) {
cout << "Nice!";
break;
}
cout << "WRONG! Try again!";
}
That being said, to answer your actual question, you can use a goto statement without any other looping instructions:
int a;
askTheUser:
cout << "What's 2+2?";
cin >> a;
if (a != 4) {
cout << "WRONG! Try again!";
goto askTheUser;
}
cout << "Nice!";
But, goto is rarely used in modern coding, it is not likely to perform any better than a do-while loop after compiler optimizations are applied, and it has limitations on how it can be used.

Answer 2

The preferred language construct for executing a block of code more than once is a loop, which can be of a for, a do-while, or a while form.
So I'd write the code as follows:
int a;
bool correctGuess = false;
while (!correctGuess) {
cout << "What's 2+2?";
cin >> a;
if (a==4) {cout << "Nice!"; correctGuess = true; }
else { cout << "WRONG! Try again!"; }
}
Another way would be the use of recursion, i.e. a function that calls itself until a particular condition is met. Yet this seems to be a to complicated approach for your scenario.
If - for any reason - you are asked to not use such kind of loops, you could use a goto-statement (though this is clearly not the preferred way to do; goto-statements are very rarely used nowadays):
int a;
loop:
cout << "What's 2+2?";
cin >> a;
if (a==4) {cout << "Nice!";}
else {
cout << "WRONG! Try again!";
goto loop;
}

Answer 3

DontDoThis:
...
goto DontDoThis;
That's it.
DontDoThis: is a "label", and goto DontDoThis jumps execution to the specified label. But, like the label's name says, DONT DO THIS! Using goto is concerned bad practice in modern coding, there are better ways to handle looping.
You should initialize a to 0 and then use a while (a != 4) loop. But that's not your question :)

Answer 4

The other loop statement is for
Another way is to use functions - they can be called repeatedly.

Answer 5

Well, if you don't want to use a while or do-while...
for (;;) //same as while(true)
{
int a;
cout << "What's 2+2?";
cin >> a;
if (a==4)
{
cout << "Nice!";
break;
}
else
{
cout << "WRONG! Try again!";
}
}