Hello, On Sun, 08 Jun 2014 18:56:47 +0300 Marko Rauhamaa <ma...@pacujo.net> wrote:
> Paul Sokolovsky <pmis...@gmail.com>: > > > Python already has that - like, len(x) calls x.__len__() if it's > > defined > > In fact, what's the point of having the duality? > > len(x) <==> x.__len__() > > x < y <==> x.__lt__(y) > > str(x) <==> x.__str__() > > etc. > > I suppose the principal reason is that people don't like UFCS. Plus > some legacy from Python1 days. I personally don't see it as "duality". There're few generic operators - the fact that they are really generic (apply to wide different classes of objects) is exactly the reason why the're defined in global namespace, and not methods. And yep, I see things like "len" as essentially an operator, even though its name consists of letters, and it has function call syntax. Then, there's just a way to overload these operators for user types, that's it. You *can* use x.__len__() but that's not how Python intends it. And like with any idea, one should not forget implementation side and efficiency - these operators are really core and expected to be used in performance-tight contexts, so they are implemented specially (optimized). Extending that handling to any function would cost either high memory usage, or high runtime cost. > Lisp & co. rigorously follow its UFCS. I think it works great, but > that is what people most ridicule Lisp for. Exactly my thinking - there're bunch of languages which follow that UFCS-like idea, likely most homoiconic (or -like) do. Or you can use plain old C ;-). So, I don't see why people want to stuff this into Python - there're lot of ready alternatives. And Python provides very intuitive and obvious separation between generic functions and object methods IMHO, so there's nothing to "fix". > > What do you think? Would you rather write/read: > > if size + len(data) >= limit: "How else could it be?" > > or UFCS-ly: > > if size.__add__(data.__len__()).__le__(limit): "OMG!" > Marko > -- > https://mail.python.org/mailman/listinfo/python-list -- Best regards, Paul mailto:pmis...@gmail.com -- https://mail.python.org/mailman/listinfo/python-list
