Arithmetic sequences in Python

[Steven Bethard]

Antoon Pardon wrote:
> Why don't we give slices more functionality and use them.
> These are a number of ideas I had. (These are python3k ideas)
> 
> 1) Make slices iterables. (No more need for (x)range)
> 
> 2) Use a bottom and stop variable as default for the start and
>    stop attribute. top would be a value that is greater than
>    any other value, bottom would be a value smaller than any
>    other value.

Just checking your intent here.  What should these do?

(2:5)    # should give me 2, 3, 4
(2:5:-1) # infinite iterator 2, 1, 0, ...?
(:5)     # start at -infinity?  what does that even mean?
(:5:-1)  # start at -infinity and go backwards?!!

I suspect you should be raising some sort of exception if the start 
isn't defined.

STeVe