[Pythonmac-SIG] (no subject)
bob at redivi.com
Sat Jan 31 14:14:23 EST 2004
On Jan 31, 2004, at 1:57 PM, Keith Nemitz wrote:
>>> huh? I mean does everyone use[-3:] instead and 0 is taboo? I'm used
>>> to the Icon programming language where "food"[-3:0] returns --> ood
>> "food"[-3:] is equivalent to "food"[-3:None] (that is, literally, how
>> it works out internally)
>> "food"[-3:0] is just backwards :) If anything, it should give you
>> "oof", but that's too confusing.
> Thank you. I knew there had to be a reason. If you think about lists
> as ring buffers, however, then "food"[-3:0]-->"ood" makes plenty of
> sense and can be very useful. My case that started this whole thread
> had to do with iterating from negative to positive, returning larger
> substrings on each iteration. It broke with the zero index. So I had
> to special case it.
They aren't ring buffers, they're arrays.. the fact you can use
negative indexes is a convenience really.. if you notice, you can do
"food"[1:100000] and you will still get "ood". You get clipped at the
boundaries when slicing.
> sigh, I wonder if adding this 'concept' to python (indexing lists as
> ring buffers) would break any existing code...
Yes, I'm sure it would.. you could make a subclass of str (or list, or
whatever) or a proxy object to address things as a ring buffer though.
> Heck while I'm at it, changing the language, might as well add nested
> comments, and (my personal favorite) record names, implemented like
> record <tuple of enums>
> tuple of enums ::= (<enum> [,enum]*)
> enum ::= <string>[= <int>]
> ...such that the keyword 'record' turns the strings into module and/or
> class scoped indexes.
You don't need language support for this, definitely not a keyword.
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