On 7/26/06, Andrew Koenig <[EMAIL PROTECTED]> wrote: > * Uniform -- the general form of the inquiry does not > depend on the particular capability being inquired about
While this makes sense from the perspective you mention, paraphrased as "different objects have different capabilities, and I want to query what capabilities this object has," I'm not convinced that any but the most uncommon uses involve enumerating the capabilities of an object. And those users are likely to be experts of the implementation. I would expect that code is more often concerned with checking no more than one or two capabilities, letting the implicit check of a raised exception do the rest. Since the times you would use __call__ and the times you would use __hash__ are so different, it seems reasonable to me that the corresponding capability check might be different. Case in point, I almost never use hash() directly; I delegate that to the dict I'm using. Whether the check were spelled "type(obj).__hash__ is not None" or "hasattr(type(obj).__hash__, "__call__")" or "try: ... except ...: ..." I wouldn't care; I've never needed to write his myself, and don't expect to. Is there code that needs to check the hashability? Sure. Does this code also need to check callability? Maybe. How about addability? Subtractibility? I doubt it. > * Free of side effects This is an ideal I agree with for some uses, although again I prefer the software version of idempotence (calling it once or many times has the same result) to side-effect-free. For many capabilities, the underlying implementation is expected to be idempotent, so I see no reason to require a separate idempotent check. We're adults here; if an implementation doesn't follow convention, it does so for a reason, and accepts the risk that someone may accidentally use it the conventional way. Michael -- Michael Urman http://www.tortall.net/mu/blog _______________________________________________ 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
