Question

I’m having issues with optional parameters on recursive functions

Here is a sample code:

private static void RecursiveFunction(int x, int optional = 0)
{
    if (x < 5)
        RecursiveFunction(x + 1, optional++);
}

When invoking the function:

RecursiveFunction(0);

I’ve got the following results (just calling this code string.Format("{0} - {1}", x, optional) in the immediate window):

"0 - 0"
"1 - 0"
"2 - 0"
"3 - 0"
"4 - 0"

Am I missing anything here? Thanks!

Answer 1

Change from:

RecursiveFunction(x + 1, optional++);
//                               ^^

To:

RecursiveFunction(x + 1, ++optional);
//                       ^^

The first one does the action then increments optional.
The second one does the action after it increments optional.

From MSDN:

++ var
var ++

The first form is a prefix increment operation. The result of the
operation is the value of the operand after it has been incremented.

The second form is a postfix increment operation. The result of the
operation is the value of the operand before it has been incremented.