number ranges

[Steven D'Aprano]

Alex Martelli wrote:

> Colin J. Williams <cjw at sympatico.ca> wrote:
>    ...
> 
>>>>I am also open to such arguments but it will be tough to convince me
>>>>that "x to y" should mean something different from what it means in
>>>>Pascal, BASIC, and English.
>>>
>    ...
> 
>>1. Why not treat '2 to 5' or '(2 to 5)' as a semi-open interval?
> 
> 
> 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.

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.

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?


> Introducing a new syntax, with semantics that "don't convince" some of
> its prominent proponents, would be self-destructive (I shudder just to
> think of the amount of time and energy we'd all be spending dealing with
> 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.



-- 
Steven.