ment">// namespaces</span>
</pre>
<p>
      Then define a placeholder for the constant itself:
    </p>
<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">boost</span><span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">math</span><span class="special">{</span> <span class="keyword">namespace</span> <span class="identifier">constants</span><span class="special">{</span>

<span class="identifier">BOOST_DEFINE_MATH_CONSTANT</sp