#18393: make Expression.series return an element of SR[[]]
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Reporter: rws | Owner:
Type: | Status: positive_review
enhancement | Milestone: sage-duplicate/invalid/wontfix
Priority: major | Resolution:
Component: calculus | Merged in:
Keywords: | Reviewers:
Authors: | Work issues:
Report Upstream: N/A | Commit:
Branch: | Stopgaps:
Dependencies: |
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Changes (by mmezzarobba):
* status: needs_review => positive_review
Comment:
Replying to [comment:10 rws]:
> I think my new posting in sage-devel
(https://groups.google.com/forum/?hl=en#!topic/sage-devel/XhOhwjjeLTM)
makes this ticket obsolete. Maybe we just need to change Pynac so that, if
an expression contains a `pseries` it will be reexpanded (making the new
order the min of all orders). What do you think?
I'm not too convinced: calling `series()` is a bit like calling `expand()`
or `normal()`, with symbolic expressions, you don't necessarily want that
to happen automatically. And (FWIW) that's also what Maple does:
{{{
#-->s := series(sin(x),x);
s := series(1*x-1/6*x^3+1/120*x^5+O(x^7),x,7)
#-->t := series(exp(x),x);
t := series(1+1*x+1/2*x^2+1/6*x^3+1/24*x^4+1/120*x^5+O(x^6),x,6)
#-->s*t;
(series(1*x-1/6*x^3+1/120*x^5+O(x^7),x,7))*(series(1+1*x+1/2*x^2+1/6*x^3+1/24*x^4+1/120*x^5+O(x^6),x,6))
#-->series(s*t,x);
series(1*x+1*x^2+1/3*x^3-1/30*x^5+O(x^6),x,6)
}}}
But perhaps I misunderstood the question?
In any case, I agree that this ticket can be closed.
--
Ticket URL: <http://trac.sagemath.org/ticket/18393#comment:12>
Sage <http://www.sagemath.org>
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