On Tue, 16 Jan 2006, it was written: > Tom Anderson <[EMAIL PROTECTED]> writes: > >> The natural way to implement this would be to make .. a normal >> operator, rather than magic, and add a __range__ special method to >> handle it. "a .. b" would translate to "a.__range__(b)". I note that >> Roman Suzi proposed this back in 2001, after PEP 204 was rejected. It's >> a pretty obvious implementation, after all. > > Interesting, but what do you do about the "unary postfix" (1 ..) > infinite generator?
1.__range__(None) >>> (-3,-5 ..) --> 'infinite' generator that yield -3,-5,-7 and so on >> >> -1. Personally, i find the approach of specifying the first two >> elements *absolutely* *revolting*, and it would consistently be more >> awkward to use than a start/step/stop style syntax. Come on, when do >> you know the first two terms but not the step size? > > Usually you know both, but showing the first two elements makes sequence > more visible. I certainly like (1,3..9) better than (1,9;2) or > whatever. I have to confess that i don't have a pretty three-argument syntax to offer as an alternative to yours. But i'm afraid i still don't like yours. :) >>> 1) "[]" means list, "()" means generator >> Yuck. Yes, i know it's consistent with list comps and genexps, but yuck >> to those too! > > I'd be ok with getting rid of [] and just having generators or > xrange-like class instances. If you want to coerce one of those to a > list, you'd say list((1..5)) instead of [1..5]. Sounds good. More generally, i'd be more than happy to get rid of list comprehensions, letting people use list(genexp) instead. That would obviously be a Py3k thing, though. tom -- Taking care of business -- http://mail.python.org/mailman/listinfo/python-list
