iterators and views of lists

[Carl Banks]

On Dec 18, 11:08 am, "Alf P. Steinbach" <al... at start.no> wrote:
> * Carl Banks:
>
>
>
> > On Dec 17, 10:00 pm, Brendan Miller <catph... at catphive.net> wrote:
> >> On Thu, Dec 17, 2009 at 6:44 PM, Steven D'Aprano
>
> >> <st... at remove-this-cybersource.com.au> wrote:
> >>> On Thu, 17 Dec 2009 12:07:59 -0800, Brendan Miller wrote:
> >>>> I was thinking it would be cool to make python more usable in
> >>>> programming competitions by giving it its own port of the STL's
> >>>> algorithm library, which needs something along the lines of C++'s more
> >>>> powerful iterators.
> >>> For the benefit of those of us who aren't C++ programmers, what do its
> >>> iterators do that Python's don't?
> >> Python iterators basically only have one operation:
>
> >> next(), which returns the next element or throws StopIteration.
>
> >> In C++ terminology this is a Input iterator. It is good for writing
> >> "for each" loops or map reduce operations.
>
> > Hmm.  I guess the main thing that's bothering me about this whole
> > thread is that the true power of Python iterators is being overlooked
> > here, and I don't think you're being fair to call Python iterators
> > "weak" (as you did in another thread) or say that they are only good
> > for for-else type loops.
>
> > The fact is, Python iterators have a whole range of powers that C++
> > iterators do not.  C++ iterators, at least the ones that come in STL,
> > are limited to iterating over pre-existing data structures.  Python
> > iterators don't have this limation--the data being "iterated" over can
> > be virtual data like an infinite list, or data generated on the fly.
> > This can be very powerful.
>
> It's good that Python iterators can do things.
>
> However, it's not the case that C++ iterators can't do those things.
>
> C++ iterators very much routinely do such things.

STL Iterators?  No.  Maybe if you're talking about boost or homemade
iterators or something I could buy it, though I'd still bs suspicious
of "routinely".


> However, C++ iterators are flawed in a way that Python iterators are not.
>
> You might say, in an analogy with control structures, that this flaw gives C++
> iterators the power of "goto" but also with all the negative baggage...

That too.


> I'm too lazy to Google, but you might search for Alexandrescu and "ranges", and
> possibly throw in "iterators" among the search terms.


Carl Banks