</p>

<pre>
v, ok = x.(T)
v, ok := x.(T)
var v, ok = x.(T)
var v, ok interface{} = x.(T) // dynamic types of v and ok are T and bool
</pre>

<p>
yields an additional untyped boolean value. The value of <code>ok</code> is <code>true</code>
if the assertion holds. Otherwise it is <code>false</code> and the value of <code>v</code> is