On Dec 19, 5:47 am, Bearophile <bearophileh...@lycos.com> wrote: > It seems you have missed my post, so here it is, more explicitly: > > http://www.boostcon.com/site-media/var/sphene/sphwiki/attachment/2009...
Interestingly, my `listagent` can be used as a lazy iterator and thus using itertools we can compose them just like Andrei's `range`. the stage: x = range(0, 20, 2); x [0, 2, 4, 6, 8, 10, 12, 14, 16, 18] y = range(10, 20); y [10, 11, 12, 13, 14, 15, 16, 17, 18, 19] z = [996, 758, 670, 236, 898, 337, 442, 452, 490, 547] from listagent import listagent import itertools chain: sorted(itertools.chain(listagent(x)[::2], listagent(y)[-1:1:-2])) [0, 4, 8, 12, 13, 15, 16, 17, 19] zip: sorted(itertools.izip(listagent(z)[1::3], listagent(x)[2::3])) [(452, 16), (758, 4), (898, 10)] stride: slicing an agent returns another one, those lazy agents! python -m timeit -s'from listagent import listagent' 'list(listagent (range(1000000))[1:-1:5][::7][10000:-10000:42])' 10 loops, best of 3: 55.5 msec per loop python -m timeit 'range(1000000)[1:-1:5][::7][10000:-10000:42]' 10 loops, best of 3: 280 msec per loop radial: not implemented `listagent` is implemented in pure Python, of course. If implemented in C, there is surprisingly little difference between a slicing `agent` like this, or a listiterator, since both will have to keep a pointer to an memory index of in the original list: the listiterator advances this pointer when we call next(), whereas the agent keeps a pointer to the starting element of the slice and return basically (PyObject *) *(p+(i*step)) on __getitem__[i]. Mutability is a just matter of exposing this pointer to Python code in a nice way. ----aht -- http://mail.python.org/mailman/listinfo/python-list
