Why is namespace composition so rarely used?
<p>In his book <em>The C++ Programming Language</em> (third edition) Stroustrup teaches to define individual components in their own namespace and import them in a general namespace.</p>

<p>For example:</p>

<pre><code>namespace array_api {    
    struct array {};    
    void print(const array&amp;) { }
}

namespace list_api {
    struct list {};        
    void print(const list&amp;) { }
}

namespace api {
    using array_api::array;
    using list_api::list;
}
</code></pre>

<p>I looks interesting, but I have never seen this approach used in practice.</p>

<p>Why is this technique is almost never used?</p>
