On Fri, Jul 12, 2002 at 06:22:05AM -0400, David Abrahams wrote:
I like the direction this is going in, but I have some reservations about any protocol which requires users to avoid using a simple method name like next() on their own multi-pass sequence types unless they intend their sequence to be treated as single-pass.
I'm not too thrilled about it, either, but I don't think it's too bad. If you implement an object with an __iter__ method you must be aware of the iteration protocol and the next method. If you put a next method on an iterable you are most probably confusing iterators and iterables and not just using the name 'next' for some other innocent purpose.
One other possibility: if x.__iter__() is x, it's a single-pass sequence. I realize this involves actually invoking the __iter__ method and conjuring up a new iterator, but that's generally a lightweight operation...
I think it is critical that all protocols should be defined by something passive like presence of attributes and attributes of attributes and not by active probing. I don't see how a future typing system could be retrofitted to Python otherwise (pssst, don't tell anyone, but I'm working on such a system...)