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copied!<p>It's actually extremely simple.</p> <p>First of all, take a look at <a href="http://www.boost.org/doc/libs/1_41_0/libs/iterator/doc/index.html" rel="nofollow noreferrer">Boost.Iterator</a> library.</p> <p>Second: you need to declare a base class (it's well explained in the example how to proceed) that will be similar to this one.</p> <pre><code>template <class Value> class BaseIterator: boost::iterator_adaptor< ... > {}; </code></pre> <p>You implement the operations to move your pointer around there. Note that because it's an adaptation over an already existing iterator, you can implement it with only a few strokes. It's really impressive.</p> <p>Third, you simply typedef it with the const and non-const versions:</p> <pre><code>typedef BaseIterator<Value> iterator; typedef BaseIterator<const Value> const_iterator; </code></pre> <p>The library explictly show you how to make the <code>const_iterator</code> version be constructible from the <code>iterator</code> version.</p> <p>Fourth, for the reverse thing, there is a special <a href="http://www.boost.org/doc/libs/1_41_0/libs/iterator/doc/reverse_iterator.html" rel="nofollow noreferrer">reverse_iterator</a> object, that is built on a regular iterator and move backwards :)</p> <p>All in all, a really elegant and yet fully functional way of defining iterators on custom classes.</p> <p>I regularly write my own container adaptors, and it's less about DRY than simply saving myself some typing!</p>

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