Numeric type conversions

[Hrvoje Niksic]

John Dann <news at prodata.co.uk> writes:

> I suppose there must be some logic in including the start position
> but excluding the end position, though it does escape me for now. I
> can understand making a range inclusive or exclusive but not a
> mixture of the two. Suppose it's just something you have to get used
> to with Python and, no doubt, much commented on in the past.

Half-open ranges are not specific to Python: for example, they're used
in Java (String.substring), Lisp (start and stop arguments to sequence
functions), and C++ (STL algorithms accept begin and end iterators
that generalize from pointers to the beginning and one-past-the-end of
an array).

Ranges so expressed have several nice properties.  The size of the
range is expressed simply as b-a, you don't need to remember to add 1.
Empty range is easily expressed as [a, a>, rather than the much less
intuitive [a, a-1] for all-inclusive ranges.  Consecutive ranges are
easily concatenated without missing or duplicating an element, so
[a, b> + [b, c> is exactly equivalent to [a, c>.