Question

Let’s say we have a simple recursion like.

int x(int a){
   if(a<10)
     x(a+1);
    else
      !STOP!
    b++;
return b;
}

Globaly:

int b=0;

In main we could have something like this:

  int p=x(1);

Is there any way to stop the recursion so that the p will be 0, this means that “b++” will never be executed.

I’ll be grateful if you could tell me some expresion to put instead of the !STOP!

But, I don’t want anything like this, I just want to stop the recursion, like break; does in a while() loop…:

int ok=0;
  int x(int a){
       if(a<10)
         x(a+1);
        else
          ok=1;
      if(ok==0)
        b++;
    return b;
    }

If there’s anything unclear about the question, just ask.

Answer 1

Why wouldn’t you do this?

int x(int a){
   if(a<10) {
      x(a+1);
      b++;
   }
   return b;
}

The thing is, though, you’re modifying a global in a recursive routine, which is not especially threadsafe and pretty sloppy. You’re returning a value that is always ignored except by the top level caller. You’re also doing something that is better off being done in a loop (but I assume that your actual case is bigger than this, or you’re a student).

You can’t really “break” the recursion – returning unwinds well enough. In oldey-timey C you might use setjmp/longjmp (and all its perils – in other words, DON’T), and in C++ you might use try/catch/throw, which will unwind the stack as well.