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    <p>Do not cast the const away, as it will break its meaning! There is a reason why the STL has a const_iterator and iterator class. If you want const correctness you will have to implement two seperate iterator classes. One of the goals of a iterator is to mimic a save pointer. So you do not want to return null if you're beyond the iteration range, you want to raise a debug assertion if this actually happens.</p> <p>A const iterator class could look something like this:</p> <pre><code>template&lt;class Item&gt; class DFSIteratorConst { public: DFSIteratorConst(const Item&amp; node) { m_pCurrentNode = &amp;node; }; const Item&amp; operator*() const { assert(!IsDone()); return *m_pCurrentNode; } void operator++() { assert(!IsDone()); m_pCurrentNode = m_pCurrentNode-&gt;next; } operator bool() const { return !IsDone(); } bool IsDone() const { return m_pCurrentNode == nullptr; } private: Item const * m_pCurrentNode; }; </code></pre> <p>A few things to note:</p> <ul> <li>consider returning a reference to the node (a const reference). This causes you to not be able to return null if the iterator is past the last element. Dereferencing a past the end iterator is usually bad behaviour and you want to find those issues during debug builds and testing</li> <li>the const iterator class has a pointer to a const element. Meaning that it can change the pointer (otherwise you would not be able to iterate) but can <strong><em>not</em></strong> modify the element itself</li> <li>the implicit conversion to bool is practical if you want to check the iterator in a while loop. This allows you to write: <code>while(it) { it++; }</code> instead of <code>while(!it.IsDone()) { it++; }</code> again, something that resembles a classic pointer.</li> <li>use <a href="http://en.wikibooks.org/wiki/More_C++_Idioms/nullptr" rel="nofollow" title="nullptr">nullptr</a> if available</li> </ul> <p>As I can see from your use of <code>std::map</code> your are already using the STL. Maybe it would be easier to use exsiting STL iterators?</p>
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    1. POIs it safe to do a const cast here?
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    1. USPhilipp Aumayr
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    1. COThere are some good points given here. Thanks. I really like the implicit bool conversion! I need a generic tree implementation for this project and STL does not supply one. I can not use boost because our team wants to avoid external dependencies as much as possible.
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    2. COwell, I consider Boost as a part of the language since the standard library is so limited anyhow. I understand people not wanting to take a dependency on any boost libs requiring linking, but the header only ones are easy to setup and mostly worry-free.
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