[Boost-users] iterator_adaptor: disguise iterator as const_iterator?

Hi all, I am trying to disguise a std container non-const iterator as a const_iterator. My guess is that iterator_adaptor could be useful for this, but I can't figure it out myself. I am trying to solve an old problem with the standard library, which is that you can't convert a const_iterator into an iterator. [There are two "solutions" to that problem, one uses distance and is expensive, the other one does a brutal conversion on bitlevel which breaks for several std implementations.] My use case: I have written a wrapper class mymap for std::map. I only want to give map::const_iterators to the users of this class. If the user wants to erase an element from the map, he must pass a const_iterator back to the wrapper class and call "mymap::erase(const_iterator)". The problem is that mymap has no way to convert the const_iterator into an iterator to call "map::erase(iterator)" in turn [there is no "map::erase(const_iterator)"]. So my idea was to write a iterator_adaptor for iterator that lets it behave like a const_iterator. Unfortunately I didn't get very far. I have to say that the documentation was not of much help to me. There are lots of complicated implementation details but only small examples. So any help is appreciated. How can I solve my problem? Side note: In the following code sample, iterator_adaptor accidentally turns a const_iterator into a non-const iterator. (Seemingly, some bit-level casting is done somewhere). Is this a bug? #include #include <map> template <class Value> class node_iter :public boost::iterator_adaptor { public: node_iter() : node_iter::iterator_adaptor_(0) {} node_iter(Value p) : node_iter::iterator_adaptor_(p) {} }; int main() { typedef std::map mymap_type; mymap_type testmap; node_iter ni(testmap.begin()); ni->second = 42; //this works, not a const_iterator anymore } ___________________________________________________________________________ Die einen haben es, die anderen werden es! http://my-mail.ch/?redirect=9905 So macht schenken richtig Freude! Schenken und Helfen mit World Vision! http://www.my-mail.ch/?redirect=1958