hat the first and second parameters are superfluous,
since the type of the base object and of the associated data field are
already implicit in the pointer to member argument: unfortunately, it is
not possible to extract this information with current C++ mechanisms,
which makes the syntax of <code>member</code> a little too verbose.
</p>

<h3><a name="const_mem_fun"><code>const_mem_fun</code> and <code>mem_fun</code></a></h3>

<p>
Sometimes, the key of an index is not a concrete data member of the element,
