At 11:41 AM 11/22/2006 -0500, Andrew Koenig wrote: > > What does it add to have to declare a class as being "Iterable", if it > > already implements __iter__? What does the notion of "Iterable" add to > > the execution *or* understanding of the code? > >Let's suppose for the sake of argument that declaring a class as being >"Iterable" adds nothing. What does that say about whether the ability to >declare other abilities is useful? I think it doesn't say much.
I submit that every other ability can be similarly defined, because the code to *implement* that ability must exist in one of three places: 1. a method of the object 2. a method of an adapter 3. a method registered somewhere, e.g. with a generic function Neither #1 nor #3 require a separate interface declaration, and #2 can be subsumed into an adaptation generic function -- which is actually what iter() does, anyway. Note that all three cases offer potential for directly verifying implementation of the ability, whereas *declaring* an ability merely adds a distinct *claim* that it has been implemented -- which then may need to be separately verified. _______________________________________________ Python-3000 mailing list Python-3000@python.org http://mail.python.org/mailman/listinfo/python-3000 Unsubscribe: http://mail.python.org/mailman/options/python-3000/archive%40mail-archive.com
