#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 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)
--
Comment (by vdelecroix):
Hi Ralf,
I think that our third item also includes CFinite sequences. The
difference is about how the function `update` is written. It might be
either
{{{
def update1(cache):
cache.append(cache[-1] + cache[-2])
}}}
or
{{{
def update2(cache):
return cache[-1]+cache[-2]
}}}
Actually, even a closed form is a special case of `update1` as one can
call `len` on the cache. Do you agree or did I miss something?
The main task of this ticket is to write precise specifications of what we
need... adapting the current implementation of `lazy_list` is
straightforward.
--
Ticket URL: <http://trac.sagemath.org/ticket/16137#comment:3>
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