 in <code class="computeroutput"><span class="identifier">inc</span></code>
      body): <a href="#ftn.boost_contract.introduction.f0" class="footnote" name="boost_contract.introduction.f0"><sup class="footnote">[2]</sup></a>
    </p>
<pre class="programlisting">postcondition assertion "x == *old_x + 1" failed: file "introduction.cpp", line 20
</pre>
<p>
      By default, when an assertion fails this library prints an error message such
      the ones above to the standard error <code class="computeroutput"