#18393: make Expression.series return an element of SR[[]]
-------------------------------+------------------------
Reporter: rws | Owner:
Type: enhancement | Status: new
Priority: major | Milestone: sage-6.7
Component: calculus | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
-------------------------------+------------------------
Comment (by nbruin):
Replying to [comment:3 rws]:
> > - How does `f=(x^2+y^2+1)` coerce into `SR[['x']]`? Note that `f` is
already an element of `SR`, so by default it would be a "constant" in
`SR[['x']]`.
> As above the `series` argument determines the name of the series
variable, so it also determines what is being done with the expression.
Already now:
That's ambiguous and not what happens by default in our current coercion:
{{{
sage: R=PowerSeriesRing(SR,name='x',default_prec=10)
sage: F=1/(1-R.0)
sage: F-x
-x + 1 + x + x^2 + x^3 + x^4 + x^5 + x^6 + x^7 + x^8 + x^9 + O(x^10)
sage: F-R.0
1 + x^2 + x^3 + x^4 + x^5 + x^6 + x^7 + x^8 + x^9 + O(x^10)
}}}
You see that SR('x') doesn't coerce to R.0 in R. You'd have to override
that somehow and that will be extremely messy: where does `sin(x)` coerce?
--
Ticket URL: <http://trac.sagemath.org/ticket/18393#comment:4>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/sage-trac.
For more options, visit https://groups.google.com/d/optout.
