[Python-Dev] PEP for adding an sq_index slot so that any object, a or b, can be used in X[a:b] notation

[Guido van Rossum]

On 2/10/06, Mark Russell <mrussell at verio.net> wrote:
>
> On 10 Feb 2006, at 12:45, Nick Coghlan wrote:
>
> An alternative would be to call it "__discrete__", as that is the key
>
> characteristic of an indexing type - it consists of a sequence of discrete
>
> values that can be isomorphically mapped to the integers.
> Another alternative: __as_ordinal__.  Wikipedia describes ordinals as
> "numbers used to denote the position in an ordered sequence" which seems a
> pretty precise description of the intended result.  The "as_" prefix also
> captures the idea that this should be a lossless conversion.

Aren't ordinals generally assumed to be non-negative? The numbers used
as slice or sequence indices can be negative!

Also, I don't buy the reason for 'as'l I don't see how this word would
require the conversion to be losless.

The PEP continues to use __index__ and I'm happy with that.

--
--Guido van Rossum (home page: http://www.python.org/~guido/)