#16137: lazy_list from various input data
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Reporter: MatthieuDien | Owner:
Type: enhancement | Status: new
Priority: major | Milestone: sage-6.2
Component: misc | Resolution:
Keywords: LazyPowerSeries, lazy_list, | Merged in:
days57 | Reviewers:
Authors: Vincent Delecroix, Matthieu | Work issues:
Dien | Commit:
Report Upstream: N/A | Stopgaps:
Branch: |
Dependencies: |
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Old description:
> The current `sage.misc.lazy_list` only deals with infinite list built
> from iterator.
> In concrete situation (as in #15673) we want to create infinite list from
> :
> - iterator
> - a function that given `n` computes the `n`-th term (also called closed
> form)
> - a function which updates a buffer of already computed values (for
> example : Newton iteration, relaxed multiplication, ...)
> - an ultimatey periodic list (from a pre-period and a period)
> - entries generated by functions (rational o.g.f. #15714, hypergeometric
> e.g.f. part of #2516)
New description:
The `lazy_list` in `sage.misc.lazy_list` only deals with infinite list
built from iterator.
In many situations we want to create infinite list from more various data:
- '''an iterator''' (current implementation),
- '''an update function''': a function that given a buffer of already
computed values compute some extra terms. This includes closed forms (i.e.
a function n -> n-th term) and algorithms that compute many terms at a
time (e.g. in the context of words: fixed point of substitutions and in
the context of power series: Newton iteration and relaxed multiplication),
- '''a pair of finite lists (pre-period, period)''' that defines an
ultimately periodic infinite sequence.
Those new lazy lists aim to be very basic Python objects. Their purpose is
to be used as fast and reliable data structures in:
- words (`sage.combinat.words`)
- continued fraction expansions/binary expansions of real numbers
- lazy power series (see #15673)
- ...
See also: rational o.g.f. #15714, hypergeometric e.g.f. part of #2516
--
Comment (by vdelecroix):
Replying to [comment:12 rws]:
> Replying to [comment:11 vdelecroix]:
> > I will roll back the previous version.
> Yes, please. Apparently, I opened the 'Modify ticket' form without
editing, you saved your change, then (after display of the yellow warning)
I saved my comment, and with it the content of the Modify ticket form.
Sorry.
It is a bit strange that there is no warning that forbid you to add
changes from version 6 when 7 is the current one... No problem, the
previous version is back.
--
Ticket URL: <http://trac.sagemath.org/ticket/16137#comment:13>
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