Making your own iterators compatible with STL iterator categories
Whatever own container data structure we come up with, in order to effectively mix it with all the STL goodness, we need to make them provide iterator interfaces. In the last section, we learned how to do that, but we do soon realize that some STL algorithms do not compile well with our custom iterators. Why?
The problem is that a lot of STL algorithms try to find out more about the iterators they are asked by us to deal with. Different iterator categories have different capabilities, and hence, there might be different possibilities to implement the same algorithm. For example, if we copy plain numbers from one std::vector to another, this may be implemented with a fast memcpy call. If we copy data from or to std::list, this is not possible any longer and the items have to be copied individually one by one. The implementers of the STL algorithms put a lot of thought into this kind of automatic optimization. In order to help...
