G'day all. Quoting ross@soi.city.ac.uk:
I don't think default definitions are quite as useless as Chris suggests: often there is a most common default; in some other cases there is a choice, but you have a family of methods that will all decide the same way, so you can delegate to one member of the family.
Well spotted! (Disclaimer: Mention of STL follows. Potential Godwin's Law issues, so proceed with caution.) One thing which isn't often appreciated about the STL is that they key thing which everything rests on is the iterator category. The details are unimportant, but the whole thing rests on what operations a specific iterator supports. The key features are: - Can the iterator be read from? - Can the iterator be written to? - Can you move it forwards (implies that it can be read from)? - Can you move it backwards (implies that you can move it forwards)? - Can you jump randomly (implies that it can be moved backwards)? The key point is that choosing which algorithm is the most efficient for some container can be determined from the iterator categories alone. In principle, it shouldn't be too hard to identify families of sequences/associations/collections all of which support a certain efficient default, and to associate the family with the collection. Cheers, Andrew Bromage