[Python-Dev] Lukewarm about range literals

[Greg Ewing]

Tim Peters <tim_one@email.msn.com>:

> I can't imagine why
> 
>     for in 0 .. len(a)-1:
> 
> isn't *equally* hated!  Requiring "-1" in the most common case is simply bad
> design.

I agree with that. I didn't mean to suggest that I thought it was
a good idea.

The real problem is in defining a..b to include b, which gives
you a construct that is intuitive but not very useful in the
context of the rest of the language.

On the other hand, if a..b *doesn't* include b, it's more
useful, but less intuitive.

(By "intuitive" here, I mean "does what you would expect based
on your experience with similar notations in other programming
languages or in mathematics".)

I rather like the a:b idea, because it ties in with the half-open 
property of slices. Unfortunately, it gives the impression that
you should be able to say

   a = [1,2,3,4,5,6]
   b = 2:5
   c = a[b]

and get c == [3,4,5].

>    for i = 1 to 10:           #  1 to 10 inclusive

Endpoint problem again. You would be forever saying

   for i = 0 to len(a)-1:

I do like the idea of keywords, however. All we need to do
is find a way of spelling

   for i = 0 uptobutnotincluding len(a):

without running out of breath.

Greg Ewing, Computer Science Dept, +--------------------------------------+
University of Canterbury,	   | A citizen of NewZealandCorp, a	  |
Christchurch, New Zealand	   | wholly-owned subsidiary of USA Inc.  |
greg@cosc.canterbury.ac.nz	   +--------------------------------------+