Range Operation pre-PEP
thomas at xs4all.net
Tue May 8 10:17:15 EDT 2001
On Tue, May 08, 2001 at 11:44:20AM +0400, Roman Suzi wrote:
> What is below is a half-baked proposal for new built-in
> Python operation. If anybody wants to raise this flag
> again and fill gaps, please do so.
> (I have not studied PEP howto much, so probably I missed
> something important.)
Just one thing: you should send it to Barry (barry at wooz.org) at least if you
want it submitted as a real PEP :)
> I hope the idea of ".." is quite simple: make special syntactic
> form for xrange (range). I am not into C to reference-implement this
> feature, so if anybody could do it...
It's not too hard to do, though the syntax might require some fiddling. (the
'.' is currently eaten by the tokenizer as part of the number.) I could do
it myself, but I'm so busy right now, I think Tim has more time than I do
> The proposed implementation uses new syntactic
> entity to specify range operation, as shown below:
> >>> for i in 1 .. 5:
> ... print i
I like, though the endpoint is debatable. Maybe Greg W. wants to do some
usage testing ? :)
> Or in extended form to specify a step:
> >>> for i in (1, 3) .. 5:
> ... print i
I don't like this. If anything, it should be the other way 'round
("1 .. (5, 3)") but even better would be something more obvious, such as
(1 .. 5) % 3
> The new operation ".." generates xrange object
> on by following rule:
I'd suggest it create an Iterator rather than an xrange object. Iterators
are new in the CVS tree, and will be in Python 2.2. Very neat things ;)
> There are no implicit forms of "..", that is, a1 and an must
> be present.
If .. created an iterator, it could be open-ended instead.
> Open issues
How about ranges of longs ? floats ? strings ? How about mixed types ?
Thomas Wouters <thomas at xs4all.net>
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