Optional parameters?

[Timoses]

On Sunday, 1 April 2018 at 15:54:16 UTC, Steven Schveighoffer 
wrote:
> I currently have a situation where I want to have a function 
> that accepts a parameter optionally.
>
> I thought maybe Nullable!int might work:
>
> void foo(Nullable!int) {}
>
> void main()
> {
>    foo(1); // error
>    int x;
>    foo(x); // error
> }


Can somebody enlighten me what this topic is about?

I thought an optional parameter would be as easy as

     void foo(int i = 0) { writeln(i); }

     void main()
     {
         int x;
         foo(x);
         foo(1);
         foo();
     }

Is the Nullable!int approach because 'i' would always 
"optionally" be 0 if not passed with above 'foo'?