m_basepoint has nothing to do with the set, isn't it in the implementation of the class that will be contained in the set? And i recommend to initialize all objects that you create, especially if you want to put them in a std::set (witch must compare objects, so: you can't add uninitialized objects to a set)

And, be careful with set, because it can contain an object only once, if this is a problem then you should look for std::multiset. Choose your containers with care.

The SGI is an implementation of STL, STL itself is only a paper, just like C++ standard, but the container interface should be the same in SGI implementation, GCC, QT, or Microsoft (i think this is done be Dinkumware) or anybody-else who implement the STL...