[Python-ideas] Where did we go wrong with negative stride?

[Ethan Furman]

On 10/30/2013 06:36 PM, MRAB wrote:
> On 31/10/2013 00:05, אלעזר wrote:
>> 2013/10/31 MRAB <python at mrabarnett.plus.com>:
>>> On 30/10/2013 23:00, Eric Snow wrote:
>>>>
>>>> On Wed, Oct 30, 2013 at 4:47 PM, Terry Reedy <tjreedy at udel.edu> wrote:
>>>>>
>>>>> I though of using a magic symbol, $, for that -- a[$-n]. But aside from
>>>>> the issue of using one of the 2 remaining unused ascii symbols for
>>>>> something that can already be done, it would not work in a slice call.
>>>>
>>>>
>>>> Is that like where you have 1 more shot on your camera and you don't
>>>> want to use it for fear that something more spectacular might show up
>>>> afterward?  (and hope that you didn't leave your lens cap on when you
>>>> finally take the picture!)  :-)
>>>>
>>> I don't think it's that bad; I count 3: "!", "$" and "?". :-)
>>>
>> Can't it be done by adding a __sub__ method to len?
>>
>> a[:len-n]
>>
>> Readable and short.
>>
> -1
>
> I don't like how it makes that function special.

Not only that, but len wouldn't know what it was subtracting from.

--
~Ethan~