Bengt Richter wrote:
> On Mon, 5 Sep 2005 18:09:51 +0200, "Fredrik Lundh" <[EMAIL PROTECTED]> wrote:
> OTOH, ISTM we must be careful not to label an alternate alpha-version
> "way to model the real world" as a "misunderstanding" just because it is
> alpha,
> and bugs are apparent ;-)
Thanks! I couldn't have said this myself. :-)
> BTW, it just occurred to me that alternate slice member semantics could be
> RELATIVE,
> EACH depending on sign. I.e.,
>
> x[start:stop:step]
>
> could mean start with x[start] as now as a starting point reference point
> element,
> then let stop be a relative range length in either direction from the
> starting point, and step absolute value indicating step size, and its sign
> indicating insertion side for zero length slices. In effect, stop would
> be a count for the slice range in either direction starting with the starting
> element
>
> s = 'abcde'
> s[2:2] => 'cd'
> s[2:-2] => 'cb'
> s[-2:-3] => 'dcb'
> s[-2:0] => ''
> s[2:0] => ''
> s[-2:-3:2] => 'db'
> r = range(10)
> r[5:0] = 'a'
> r => [0, 1, 2, 3, 4, 5, 'a', 6, 7, 8, 9]
> r[-2:0:-1] = 'b'
> r => [0, 1, 2, 3, 4, 5, 'a', 6, 7, 'b', 8, 9]
> r[-2:0] = ['c', 'd']
> r => [0, 1, 2, 3, 4, 5, 'a', 6, 7, 'b', 8, c, d, 9]
Interesting, so it would be...
slice( position, count, step )
Items are addressed directly so there's no 'gap's to account for.
> note that slice assignment would work by iterating through the right hand
> sequence, which could do interesting things:
>
> r = range(6)
> r[3:-2] = 'ab'
> r => [0, 1, 'b', 'a', 4, 5]
> but two reverse relative slices match order, so
> r = range(10)
> r[5:-3] = range(10)[-1:-3] # rh seq is 9, 8
> r => [0, 1, 8, 9, 4, 5]
>
> I think this is kind of interesting, and I probably wouldn't have thought of
> it if I had not been for Ron's enthusiasm for his "misunderstanding" ;-)
>
> In a way, "misunderstandings" are the mutations of open source evolution of
> ideas,
> most of which die, but some of which mutate again and may occasionally
> survive.
> So we need them ;-)
Here's another possible "misunderstanding".
(or alternative alpha-version) ;-)
Have you thought of using a slice object as a buffer pointer for
indirect operations?
r = range(100)
d = [10:20]
r.range_add(d,5) # Adds 5 to items in range d
d = d[5:] -> [15:20] # relative range modification.
# slice of a slice object
r.range_sub(d,3) # subtract 3 from items in range d
Or more flexible ...
r.range_modify(d, add(), 5)
Using your suggestion that would be...
r = range(100)
d = [10:10]
r.range_add(d,5)
d = d[5:] -> [15:5] # interesting symmetry.
r.range_sub(d,3)
Of course adding and subtracting slice objects could also be possible.
d = [10:20]
e = [15:25]
f = d + e -> [10:25]
or ...
d = [10:10]
e = [15:10]
f = d + e -> [10:15]
Cheers,
Ron
> Regards,
> Bengt Richter
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