Question

At the risk of sounding stupid, why does the following method return the result instead of the value 1 when the conditional block equates to true?

public long Recursive(int Input)
{
    if (Input <= 1)
        return 1;
    else
        return Input * Recursive(Input - 1);
}

Answer 1

It does return 1 at the point that Input == 1.

But the 1 returned is used with the prior call, multiplied by Input, the return value of which is used with the prior call, multiplied by Input, the return value of which is used with the prior call, multiplied by Input, the return value of which is used with the prior call, multiplied by Input… until you have gotten back to the first call to Recursive.

Try to see what happens when you call Recursive with the value 3:

 - input is not 1, so it calls Recursive with the value 2
   - input is not 1, so it calls Recursive with the value 1
     - input is 1, 1 is returned
   - 2 * 1 is returned
 - 3 * 2 is returned