CoCoA » CoCoALib

I think it would be nice to be able to use CoCoALib iterators with the "new" for loop syntax. I note also that C++20 introduced "ranges": something like a pair of iterators (begin, end). We should study this, and consider whether using them would be a good way of adapting CoCoALib iterators to more general C++ use. An alternative is to define an end iterator for each iterator type; or maybe a "universal" end object which may be compared to any CoCoALib iterators -- the comparison would effectively call IsEnded. I admit that it does "feel strange" having a single "end iterator object" for all iterators -- quite unlike the way C++ iterators work!

The other point is what should happen if a user tries to advance a CoCoALib iterator which is already ended? I think there are two likely options: throw an error, or do nothing. The "do nothing" option has the extra risk of possibly allowing unexpected infinite loops; the "throw an error" option is probably more user-friendly. Either way, we must check through every implementation and ensure that it behaves according to design -- I suspect that the current situation is a messy mixture of behaviours.