Alex Martelli wrote: > Steven D'Aprano <[EMAIL PROTECTED]> wrote: > ... > >>>Reread the part I quoted above: at least some of the proponents of this >>>syntax appear to be totally ignorant of 30 years of literature and >>>practice of programming, "it will be tough to convince" them that closed >>>intervals are a terrible mistake and semi-open ones the only way to go. >> >>I intellectually understand that semi-open intervals >>are the only way to go. But reading the words, the part >>of my brain that speaks English cries out for a closed >>interval. Bad brain. > > > Human brain -- it's harder for non-native-speakers like me to judge the > associations of certain English words in a native speaker's brain. > > >>Given the overwhelming benefit of semi-closed >>intervals, I wish to amend my proposal to follow Alex's >>suggestions, namely: >> >>for i in (1 to 10 by 3): >> print i >> >>should print 1 4 7. > > > But that would be an "attractive nuisance" to many other native speakers > like you, who would instinctively think of a closed interval. Maybe > 'upto' rather than 'to', as somebody else suggested, would ease that. > > >>That would make (a to b by c) equivalent to >>range(a,b,c) except that it returns an iterator rather >>than a list. Hmmm... putting it that way, the new >>syntax actually costs 1 keystroke, or saves 1 if you >>put spaces after the commas in the range expression. >>Does it add enough clarity and ease of understanding to >>justify two new keywords? > > > No, of course not. And if we use upto, we'll need a downto as well, a > third keyword, for loops with negative step. range should return an > iterator in Python 3.0 (maybe in 2010?-) and xrange will then go away, > so the only issue is whether syntax sugar for it is SO badly needed as > to justify 2/3 new keywords. > > >>>whines about it); Python is clearly much better off if such people run >>>away to Ruby, with its (expletive deleted) a..b AND a...b syntaxes just >>>to ensure maximum confusion;-). >> >>Ruby uses both .. and ...? Now I'm frightened. > > > I _like_ Ruby, mostly, but yes, it has both a..b AND a...b, one of them > to indicate a semi-open interval and the other to indicate a closed one > (I believe the three dots are for the semi-open, but it could be the > other way 'round) -- I don't remember how it indicates a step. I do > think this is a wart (lack of visual or mnemonic distinction), though > I'm sure Ruby enthusiasts would not agree. > > > Alex http://www.ruby-doc.org/docs/ProgrammingRuby/ It seems that .. and ... are Range class constructors.
Range.new(a, b, exclusive= True) is equivalent to Python's range(a, b) i.e. Ruby's a...b There appears to be no provision for a stride. Ruby's choice between .. and ... seems a little perverse. I would expect '...' to deliver a little more than '..'. I guess one could consider Python's range() as a constructor for the List class. Steven D'Aprano suggested that 1 to 10 by 3 should create an iterator. What are the benefits of this as compared with a Python List? Could we not have 1 ... 10 ... 3 to mean the same thing and then there would be no need for extra reserved words? Colin W. -- http://mail.python.org/mailman/listinfo/python-list
