#16137: lazy_list from various input data
-------------------------------------+-------------------------------------
Reporter: MatthieuDien | Owner:
Type: enhancement | Status: new
Priority: major | Milestone: sage-6.4
Component: misc | Resolution:
Keywords: LazyPowerSeries, | Merged in:
lazy_list, days57 | Reviewers:
Authors: Vincent | Work issues:
Delecroix, Matthieu Dien | Commit:
Report Upstream: N/A | 37e67683e7a2f10152ba3a01b8aed508fe92f0f1
Branch: | Stopgaps:
u/MatthieuDien/lazy_list_from_various_input_data|
Dependencies: |
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Comment (by mantepse):
Comments (IMPORTANT: I have hardly any understanding of python/cython
necessities, so some of these may be very naive or stupid)
1.) Concerning the *original* `lazy_list`, I would have expected that
{{{
sage: from sage.misc.lazy_list import lazy_list
sage: l = lazy_list(Primes())
sage: l[:100]
}}}
returns a list, not a lazy list. (I'm aware of `l[:100].list()`, but this
seems inconsistent: `l[0]` also returns an element, not a lazy list)
Do you know a reason for this decision? Possibly it's more practical,
right?
2.) Concerning the *new* `lazy_list` some things clearly don't work:
{{{
sage: from sage.misc.lazy_list import lazy_list_from_iterator
sage: from itertools import count
sage: l2 = lazy_list_from_iterator(count()); l2
lazy list [0, 1, 2, ...]
sage: l2[:10]
(0, 10, 1)
sage: l2[10]
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
<ipython-input-8-02ea92939ca1> in <module>()
----> 1 l2[Integer(10)]
/home/rubey/sage-lazy_list/local/lib/python2.7/site-
packages/sage/misc/lazy_list.so in
sage.misc.lazy_list.lazy_list_from_iterator.__getitem__
(build/cythonized/sage/misc/lazy_list.c:6074)()
TypeError: 'int' object is not iterable
}}}
3.) Yes, I think that `lazy_list_from_fun` (besides: I would prefer
`lazy_list_from_function`) should do precisely as you say. Currently, it
doesn't: I would have expected the following to return
a lazy list full of empty lists...
{{{
sage: l3 = lazy_list_from_fun(lambda a, b: b); l3
lazy list [[[...], [...], [...], [...]], [[...], [...], [...], [...]],
[[...], [...], [...], [...]], ...]
}}}
4.) There are now two entry points: `lazy_list_from_fun` and
`lazy_list_from_iterator`. I would expect that in the end there is also a
general purpose constructor which decides what to use
depending on the type of the argument, right?
--
Ticket URL: <http://trac.sagemath.org/ticket/16137#comment:23>
Sage <http://www.sagemath.org>
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