The order of function doesn't allow me to write reusable codes in c++

Question

I have two functions that is dependent on each other, but the order of the function in C++ limit my ability to write reusable codes. For example let say, I want to use functionA in a functionB then

functionB has to be above functionA.

but what if

functionB is using functionA and functionA is using functionB as well? it will gives error

Here's the code, and the order of the functions in c++

void getAnswer(string answer) {

            mainProgram();

}

void mainProgram() {
   getAnswer("awesome");

}

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

    mainProgram();


    return 0;
}

As you can see mainProgram() is using getAnswer() function and vice versa.

I can just solve this problem by deleting the getAnswer() function and simply throw every code from getAnswer() to mainProgram() but the problem with that , is I will write a repetitive code for about 5 times, and it will look really messy.

Am I the only one to notice an "infinite" recursion here? – anderas Jun 24 '15 at 09:06 — anderas, Jun 24 '15 at 09:06

score 5 · Accepted Answer · edited May 23 '17 at 10:26

5

You need to forward-declare your function:

//forward declaration
void mainProgram();

void getAnswer(string answer) {
    //sees the declaration above, doesn't need the definition
    mainProgram();
}

//now we define the function
void mainProgram() {
   getAnswer("awesome");
}

This kind of thing should be covered in your introductory book. If you don't have a good introductory book, get one.

Also note that you will need to terminate this mutual recursion at some point.

edited May 23 '17 at 10:26

Community

1
1

answered Jun 24 '15 at 08:46

TartanLlama

63,752
13
157
193

infinite recursion, how do i solve it? – airsoftFreak Jun 24 '15 at 09:07
4

@airsoftFreak With your brain and an exit condition. – Blacktempel Jun 24 '15 at 09:08
@Blacktempel Instructions not clear, smeared brain all over C++. – Jun 24 '15 at 09:17
Have a check like `if (shouldExit) return; else mainProgram();`. – TartanLlama Jun 24 '15 at 09:21
Got it, i thought i need to do something exquisite like using c++ special method or something. – airsoftFreak Jun 24 '15 at 09:23

score 3 · Answer 2 · answered Jun 24 '15 at 08:46

What you are looking for is called forward declaration.

Define the names and parameters of the functions first, and then declare their body. This allows two functions to be dependent on each other.

void mainProgram(); // this is a declaration of your function.

void getAnswer(string answer) // the body of the function which can call the declared function.
{
    mainProgram();
}

void mainProgram() // the body of the function which was declared earlier.
{
    getAnswer("awesome");
}

score 0 · Answer 3 · answered Jun 24 '15 at 09:13

0

In this case it is infinite of function calling .However if your not sure about order function calling and it's declaration, use forward declare in the beginning of the file.

answered Jun 24 '15 at 09:13

Venkata Naidu M

351
1
6

The order of function doesn't allow me to write reusable codes in c++

3 Answers3