Heya Everyone, I am trying to create a generic way to extract a list of objects from another list of objects. Let me explain! Say I have a vector (or any container with fwd iterators and value_type) that contains objects that have a function which returns a long (could actually be any type). I want to iterate over that vector and extract each of the longs into a list (or any container that supports push_back and defines value_type). Something like the following: class HandleClass { public: long handle() const { return val_++; } private: static long val_; }; // ... std::vector<HandleClass> listOfHcs; // ... fill listOfHcs here std::list<long> needToFill; OK so far. I then wrote this extraction function (yes, there are many ways I could have done this - with a functor and using foreach is another possibility worth exploring, but not now :) ). template < class ReturnContainer, class FwdIterator > void Extract(const FwdIterator & itBegin, const FwdIterator & itEnd, ReturnContainer & container, boost::function1<ReturnContainer::value_type, FwdIterator::value_type> f) { for (FwdIterator it = itBegin ;it != itEnd; ++it) { container.push_back(f(*it)); } }; And I was able to do this: Extract(listOfHcs.begin(), listOfHcs.end(), needToFill, &HandleClass::handle); And it worked like a charm. needToFill gets filled and I was happy. :) However we also had containers of _pointers_to_ HandleClasses. So in some cases our vector looked like: std::vector<HandleClass *> listOfHcs; Yet the same code worked! I couldn't, and can't, for the life of me understand what was going on (I expected that I would have to wrap the (*it) in a boost::remove_pointer which worried me because my compiler - MSVC7.0 - doesn't support partial template specialization). Don't get me wrong, I'm happy that it work but can anyone explain what fandangelory is going on inside boost::function (or perhaps it's some C++ magic?) to allow this? Cheers, Matt