Lawrence D'Oliveiro <l...@geek-central.gen.new_zealand> writes: > In message <87lj52kwln.fsf....@metalzone.distorted.org.uk>, Mark Wooding > wrote: > > > One option is to implement a subclass which implements the additional > > protocol. > > This is why I think object orientation ruins your ability to think > properly. For “protocol” read “function”. If you want to implement a > new function, then implement a new function, why do you have to go > through this “subclassing” malarkey just to do something so simple.
Functions don't do type-dependent dispatch, which was, of course, the whole point. A `protocol' is a collection of messages understood by a number of different kinds of objects, causing potentially object-specific behaviour. I gave the explicit example of serialization: string probably serializes differently from an integer or a list. The `__str__' and `__repr__' methods form a simple protocol for object printing, as an additional example. The `str' and `repr' functions provides a potentially useful external entry points into the protocol, but they work by doing a type-dependent dispatch on the argument -- calling the appropriate method. Object orientation isn't useless or an impediment to clear thinking. It does seem to have turned into a bizarre kind of religion by some, and many `mainstream' languages provide very poor object orientation features (yes, Java and C#, I'm looking at you). But OO can be useful. I think the notion of `protocol' is central to coherent OO design, but this seems largely overlooked in much of the literature I've read. This may mean that many people are muddled about what OO is actually for. -- [mdw] -- http://mail.python.org/mailman/listinfo/python-list
