Nesting int main() inside int main()

Question

I am trying to make the simplest of all games, but with a loop function.

I'm given the error "a function-definition is not allowed here before '{', as well as a whole list of [Error] expected '}' at end of input.

Am I not allowed to nest int main() within another? Is that my issue at all? How do I accomplish this code without the nesting?

My knowledge and experience extend no more than a few chapters in two books.

#include <iostream>
#include <cstdlib>
#include <ctime>

using namespace std;

int main()
{
    char again = 'y';
    while (again == 'y')


    int main()
        {

            srand(static_cast<unsigned int>(time (0)));
            int secret = rand() % 100 +1;
            int tries = 0;
            int guess;
            cout << "\tGuess the random number\n\n";

            do 
                {
                    cout << "Enter a guess: ";
                    cin >> guess;
                    ++ tries;
                    if (guess > secret)
                        {
                            cout << "Too High!\n\n:";
                        }
                    else if (guess < secret)
                        {
                            cout << "Too Low!\n\n";
                        }
                    else 
                        {
                            cout << "\nThat's It! You go it in " << tries << " guesses!\n";
                        }
} while (guess != secret);
}

cout << "\n\tWould you like to play again? (y/n): ";
char again;
cin >> again;


}

*"Is that my issue at all?"* - yes. WTH are you trying to accomplish? — LogicStuff, Apr 12 '16 at 18:47
Can you try to put a semicolon after the nested main like so? `int main();`. This should make it work and have it nested — Johannes Schaub - litb, Apr 12 '16 at 18:47
If you can't bind `main` as the unique entry point of your program then you are Over the Bounding Main. — stark, Apr 12 '16 at 18:50
You are not allowed to define **any** function inside another function. There's nothing special about `main` here. What is it that you're trying to accomplish? — Pete Becker, Apr 12 '16 at 18:53
@JohannesSchaub-litb Yes, Thank you very much, it runs now. It doesn't display anything, but at least it runs — Christopher Mcpherson, Apr 12 '16 at 18:55
@JohannesSchaub-litb, comment worth an answer. I would personally upvote it. — SergeyA, Apr 12 '16 at 18:55
`while (again == 'y') { ... }` is how you write a loop, with your current thinking the `do { ... } while` loops also needs `int main()`. — LogicStuff, Apr 12 '16 at 18:55
@JohannesSchaub-litb: But you could just as well remove the line entirely. It would make more sense. — Fred Larson, Apr 12 '16 at 19:09
@FredLarson i am unsure. you would lose the nested function. — Johannes Schaub - litb, Apr 12 '16 at 19:13
@JohannesSchaub-litb: What? There are no nested functions in C++! — Fred Larson, Apr 12 '16 at 19:17
@FredLarson possibly it's called different in the Standard. Not necessarily "nested". Perhaps "contained" or something. — Johannes Schaub - litb, Apr 12 '16 at 19:20
@JohannesSchaub-litb: http://stackoverflow.com/questions/4324763/c-can-we-have-functions-inside-functions — Fred Larson, Apr 12 '16 at 19:23
@Johannes Schaub-litb no, it is correct. `int main();` inside a function is a declaration and not a definition. The only way you can define functions inside other functions is via lambdas. — Otomo, Apr 13 '16 at 08:31
@otomo, incorrect, it has been possible since the first C++ release to define functions inside other functions. See the linked question thread — Johannes Schaub - litb, Apr 13 '16 at 09:55
@JohannesSchaub-litb I only see a thread which elaborates that it is not possible unless you use lambdas. Your solution with the added semicolon does exactly what I said--it _declares_ a function. The function body is missing so it cannot be a definition. There is a support for nested functions in GNU C but it is not standard compliant C++. — Otomo, Apr 13 '16 at 10:25
@tomo the linked question itaelf says (against the rules, since it was not posted as an answer) that it is possible without lambdas — Johannes Schaub - litb, Apr 13 '16 at 13:28

Lilith Daemon · Answer 1 · 2016-04-12T19:10:25.873

Your issue is nesting a main function inside of the existing main function. (This is not allowed.) In general, (With the exception of some stuff you can do with structs/lambdas which approximate that kind of functionality) you shouldn't nest functions inside of each-other. If you merely remove the function declaration, then your code should work fine:

#include <iostream>
#include <cstdlib>
#include <ctime>

using namespace std;

int main()
{
    char again = 'y';
    while (again == 'y')

        {

            srand(static_cast<unsigned int>(time (0)));
            int secret = rand() % 100 +1;
            int tries = 0;
            int guess;
            cout << "\tGuess the random number\n\n";

            do
                {
                    cout << "Enter a guess: ";
                    cin >> guess;
                    ++ tries;
                    if (guess > secret)
                        {
                            cout << "Too High!\n\n:";
                        }
                    else if (guess < secret)
                        {
                            cout << "Too Low!\n\n";
                        }
                    else
                        {
                            cout << "\nThat's It! You go it in " << tries << " guesses!\n";
                        }
                } while (guess != secret);

            cout << "\n\tWould you like to play again? (y/n): ";
            cin >> again;
        }


}

CodeMouse92 · Answer 2 · 2016-04-12T19:09:46.140

As far as I know, you cannot nest int main() inside of int main() for a number of reasons. In general, you can't define one function inside of another (defining "locally"). However, even if you can, your desire to do so should be a massive red flag that your design is off.

NOTE: As Nathan Oliver pointed out in the comments, you can forward-declare a function "locally" (within another function), but the actual implementation must be outside. Even doing this, you should usually second-guess your design at this point.

You need to be asking yourself what you're trying to do.

Are you wanting to group code together under a function to call repeatedly? Then create a separate function (with a different name) outside of main().
Are you wanting to repeat code? If so, you need a loop or a recursive function structure.
Are you wanting to split up some behavior into several functions, but hide all but one function involved? If so, look into classes (not necessarily objects - you can also have static classes.)

Those are just three of many possibilities, and deciding exactly what you want to do and how you want to do it is your responsibility alone to decide, as a programmer.

Brief recap: as far as C++ (and C) are concerned, if you're trying to declare any function inside any other function, you are doing something seriously wrong in design.

On a more technical note, you should also understand precisely what int main() is. It is a special function that is the entry point for your program. No C or C++ program can run without an int main().

You have to have a single instance of this function in main.cpp in order for your program to work. If you have more than one int main(), the computer cannot likely will not be able to find the entry point.

Besides that, having more than one function called main() anywhere in your code is a great way to confuse yourself and others.

In short, you should only have one int main() per program, no exceptions.

local function definitions are illegal period, It is not just limited to `main()`. — NathanOliver, Apr 12 '16 at 18:53
Also note that declaring a function locally is totally okay: http://coliru.stacked-crooked.com/a/76f71f801cf41043 — NathanOliver, Apr 12 '16 at 18:55
Updated to that effect. Also, your link isn't working for me, @NathanOliver. — CodeMouse92, Apr 12 '16 at 18:59
Interesting that the link is not working. try this one: https://ideone.com/AOHK3w — NathanOliver, Apr 12 '16 at 19:06
@NathanOliver Ahh! I see what you mean now - it can be forward declared, but the implementation cannot be placed there. — CodeMouse92, Apr 12 '16 at 19:07
Yes. You can locally declare but not local define a function. — NathanOliver, Apr 12 '16 at 19:09

Nesting int main() inside int main()

2 Answers2