Re: extremal case of component extraction

[Bill Allombert <Bill.Allombert@math.u-bordeaux.fr>]

On Wed, Dec 10, 2014 at 06:12:28PM +0100, Karim Belabas wrote:
> P.S. In the above correspondence a --> ia, I didn't state what a = 0
> encodes: it's undefined. It *should* raise an exception but the
> implementation currently uses
> 
>   v[0..b]
> 
> as an alias for
> 
>   v[^b]   \\ remove index=b entry
> 
> And 
> 
>   v[a..0]
> 
> as an alias for
> 
>   [v[a]]
> 
> I'm not sure about the reason for the final one...

Actually, a..0 is an alias for a..a
But as implemented, this is the converse:
^b is short-hand for 0..b
a  is short-hand for a..0 _except_ in the v[a] case.

Cheers,
Bill