[Python-ideas] Implement comparison operators for range objects

[Sven Marnach]

Steven D'Aprano schrieb am Do, 13. Okt 2011, um 04:33:49 +1100:
> >When implementing '==' and '!=' for range objects, it would be natural
> >to implement the other comparison operators, too (lexicographically,
> >as for all other sequence types).
> 
> I don't agree. Equality makes sense for ranges: two ranges are equal
> if they have the same start, stop and step values. 

No, two ranges should be equal if they represent the same sequence,
i.e. if they compare equal when converted to a list:

    range(0) == range(4, 4, 4)
    range(5, 10, 3) == range(5, 11, 3)
    range(3, 6, 3) == range(3, 4)

> But order
> comparisons don't have any sensible meaning: range objects are
> numeric ranges, integer-valued intervals, not generic lists, and it
> is meaningless to say that one range is less than or greater than
> another.

Well, it's meaningless unless you define what it means.  Range objects
are equal if they compare equal after converting to a list.  You could
define '<' or '>' the same way.  All built-in sequence types support
lexicographical comparison, so I thought it would be natural to bring
the only one that behaves differently in line.  (Special cases aren't
special enough...)

This is just to explain my thoughts, I don't have a strong opinion on
this one.

I'll try and prepare a patch for '==' and '!=' and add it to the issue
tracker.

Cheers,
    Sven