Valid Function Declaration : <p>I have an abstract C++ Question and I'm having an argument with someone about this:</p>

<p>Which one of these could be a valid function declaration:</p>

<pre><code>int f ( int i=0, int j );
int f (int j, void k);
int f (int i, int u=0 );
int f (int * = 0);
</code></pre>
