oints" to  the end of a string.  The 
<a target="filter_iterator" href="../../iterator/doc/filter_iterator.html">
<code style="white-space: normal">filter_iterator</code></a> is implemented
in this way so it can't be used in our context. So, for implementation of this iterator, 
space removal is deferred until the iterator actually is dereferenced.

<h4>Comparison</h4>
The default implementation of iterator equality of <code style="white-space: normal">iterator_adaptor</code> just
invokes the equality opera