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a couple small edits to the iterator adaptor tutorial

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[SVN r21700]
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Jeremy Siek
2004-01-13 19:35:41 +00:00
parent df66940f0f
commit 11770763df
3 changed files with 23 additions and 13 deletions
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@ -348,17 +348,19 @@ to who-knows-where? The most we can do with that incremented
position is to compare another <tt class="literal"><span class="pre">node_base*</span></tt> to it. In other
words, the original iterator traverses a one-element array.</p>
</div>
<p>You probably didn't think of it that way, but the <tt class="literal"><span class="pre">node_base*</span></tt>
<p>You probably didn't think of it this way, but the <tt class="literal"><span class="pre">node_base*</span></tt>
object which underlies <tt class="literal"><span class="pre">node_iterator</span></tt> is itself an iterator,
just like all other pointers. If we examine that pointer closely
from an iterator perspective, we can see that it has much in common
with the <tt class="literal"><span class="pre">node_iterator</span></tt> we're building. First, they share most
of the same associated types (<tt class="literal"><span class="pre">value_type</span></tt>, <tt class="literal"><span class="pre">reference</span></tt>,
<tt class="literal"><span class="pre">pointer</span></tt>, and <tt class="literal"><span class="pre">difference_type</span></tt>). Second, even much of the
<tt class="literal"><span class="pre">pointer</span></tt>, and <tt class="literal"><span class="pre">difference_type</span></tt>). Second, even some of the
core functionality is the same: <tt class="literal"><span class="pre">operator*</span></tt> and <tt class="literal"><span class="pre">operator==</span></tt> on
the <tt class="literal"><span class="pre">node_iterator</span></tt> just return the result of invoking the same
the <tt class="literal"><span class="pre">node_iterator</span></tt> return the result of invoking the same
operations on the underlying pointer, via the <tt class="literal"><span class="pre">node_iterator</span></tt>'s
<a class="reference" href="iterator_facade.html#implementing-the-core-operations"><tt class="literal"><span class="pre">dereference</span></tt> and <tt class="literal"><span class="pre">equal</span></tt> member functions</a>)</p>
<a class="reference" href="iterator_facade.html#implementing-the-core-operations"><tt class="literal"><span class="pre">dereference</span></tt> and <tt class="literal"><span class="pre">equal</span></tt> member functions</a>). However, the <tt class="literal"><span class="pre">operator++</span></tt> for
<tt class="literal"><span class="pre">node_iterator</span></tt> behaves differently than for <tt class="literal"><span class="pre">node_base*</span></tt>
since it follows the <tt class="literal"><span class="pre">m_next</span></tt> pointer.</p>
<p>It turns out that the pattern of building an iterator on another
iterator-like type (the <tt class="literal"><span class="pre">Base</span></tt> <a class="footnote-reference" href="#base" id="id3" name="id3"><sup>1</sup></a> type) while modifying
just a few aspects of the underlying type's behavior is an
@ -430,13 +432,15 @@ std::iterator_traits&lt;Iterator&gt;::<em>some-associated-type</em>
<a class="reference" href="reverse_iterator.html"><tt class="literal"><span class="pre">reverse_iterator</span></tt></a> and the other Boost <a class="reference" href="index.html#specialized-adaptors">specialized iterator
adaptors</a> to get an idea of the sorts of things you can do with
<tt class="literal"><span class="pre">iterator_adaptor</span></tt>. In particular, have a look at
<a class="reference" href="counting_iterator.html"><tt class="literal"><span class="pre">counting_iterator</span></tt></a>, which demonstrates that <tt class="literal"><span class="pre">iterator_adaptor</span></tt>'s <tt class="literal"><span class="pre">Base</span></tt> type needn't be an iterator.</p>
<a class="reference" href="transform_iterator.html"><tt class="literal"><span class="pre">transform_iterator</span></tt></a>, which is perhaps the most straightforward
adaptor, and also <a class="reference" href="counting_iterator.html"><tt class="literal"><span class="pre">counting_iterator</span></tt></a>, which demonstrates that
<tt class="literal"><span class="pre">iterator_adaptor</span></tt>'s <tt class="literal"><span class="pre">Base</span></tt> type needn't be an iterator.</p>
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