EXC_BAD_ACCESS in simple c++ XCODE program

Question

I'm new to c++ and I'm trying to make a calculator. I designed this function for the purpose of getting factorial of a number:

     int factorial(int num1) {
    int sum;
    if (num1 == 1) {
        sum = 1;
    }
    else {
        sum = factorial((num1 - 1) * num1);
    }

    return sum;
}

Whenever I try and compile this, however, I get the error EXC_BAD_ACCESS on the

int factorial(int num1)

Any idea what's going on? I'm using XCODE.

Answer 1

Your definition leads to an infinite recursion whenever num1 is not 1.

Do the maths yourself:

  factorial(2)
= factorial((2-1) * 2)
= factorial(2)
= factorial((2-1) * 2)
= ...

or

  factorial(3)
= factorial((3-1) * 3)
= factorial(6)
= factorial((6-1) * 6)
= factorial(30)
= ...

The recursive definition of the factorial function is not

factorial(n) = factorial((n - 1) * n)

it is

factorial(n) = n * factorial(n - 1)

(And the factorial is not a sum, but a product.)