er = boost::parameter;''') -->
<!-- @example.append('''
int main()
{}''') -->
<!-- @test('run') -->
<p>In the example above, the string <tt class="docutils literal">&quot;hello, world&quot;</tt> is constructed
despite the fact that the user passed us a value for <tt class="docutils literal">s3</tt>.  To
remedy that, we can compute the default value <em>lazily</em> (that is,
only on demand), by using <tt class="docutils literal"><span class="pre">boost::bind()</span></tt> to create a function
object.</p>
<!-