foreach, an analogy

[Karen Lanrap]

Sean Kelly wrote:

> I'm not sure I understand.  foreach for a class merely calls
> opApply in that class, so the designer of the class is
> responsible for writing the iteration code.

Yes, that is the current state. But is it suitable for any project?


| Iterators have caused problems in the research on ownership
| systems. Typically, the dilemma comes up of whether the
| collection should own/contain the iterator or vice versa. Some
| systems provide solutions that allow iterators to be programmed,
| but they do not address the problem of verifying their
| functional behavior.

"Iterators revisited: proof rules and implementation",
http://research.microsoft.com/projects/specsharp/papers/Iterators.pdf