What components are essential to a C++ project which are not found in a common library?
<p>For most C++ projects Boost covers a lot of ground component wise but often used solutions and idioms require some boiler plate or ground work. What do you consider so essential that you would have it in every project and thus have it in a small "library"?
Some things I thought of:</p>

<ul>
<li>Singleton base-class (somebody will think he needs it, so he can do it properly)</li>
<li>ScopeGuard</li>
<li>Factory base-class</li>
<li>any_iterator</li>
</ul>

<p>(The last two are in Loki but Loki has overlap with Boost and people are hesitant to use it.)</p>

<p>Edit: I might should add that I don't ask about the usual extensions of the standard library e.g. <code>copy_if</code>.</p>
