e classes are implemented.
Beginning with possibly the simplest class in the library, is_void&lt;T&gt;
has a member <i>value</i> that is true only if T is void.</p>

<pre>template &lt;typename T&gt; 
struct is_void
{ static const bool value = false; };

template &lt;&gt; 
struct is_void&lt;void&gt;
{ static const bool value = true; };</pre>

<p>Here we define a primary version of the template class <font
size="2" face="Courier New">is_void</font>, and provide a full-specialisation
when T is void. While full