Multi argument for implicit conversion
<p>For a constructor with multiple arguments...</p>

<p>For example:</p>

<pre><code>class C {
public:
    C(int a=1, int b=2){ cout &lt;&lt; a &lt;&lt; ", " &lt;&lt; b &lt;&lt; "\n"; }
}

int main(){
    C a(10), b = 20;
}

output:
10, 2
20, 2
</code></pre>

<p>How do I just assign value to the 2nd parameter? So that I can get "1, 20" without knowing the default values? Or is that that I must always assign value to the argument that precedes before I can use the arguments behind?</p>

<p>And how do I implicitly assign all the parameters? If I can't do that, why? For the above example (as I am new to C++), I once thought I would get "10, 20" as output instead. </p>
