#18092: evaluating symbolic expressions (without conversion to SR, i.e.,
staying in
ring of values)
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Reporter: | Owner:
dkrenn | Status: needs_info
Type: | Milestone: sage-6.6
enhancement | Resolution:
Priority: major | Merged in:
Component: | Reviewers:
symbolics | Work issues:
Keywords: sd66 | Commit:
Authors: | 276f0f3d3583c66c7e137350c578e8588c9b236d
Daniel Krenn | Stopgaps:
Report Upstream: N/A |
Branch: |
u/dkrenn/SR/eval |
Dependencies: |
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Comment (by dkrenn):
Replying to [comment:14 nbruin]:
> The general idea is that the result of arithmetic only depends on the
parents of the input data, not on the values of the input data (because
the idea is that these things implement maps, which have domains and
codomains). When you evaluate a SR element at a non-symbolic value, you
don't know if the result can live in the parent of the original result
(e.g., `(sin(x)+y).subs(y=1)`).
True.
> The appropriate solution is probably to first *convert* your symbolic
expression to a parent where the parent is the desired thing, e.g.
> {{{
> sage: f = SR(1+x)
> sage: R.<t>= ZZ[[]]
> sage: P=R['x']
> sage: P(f)(x=t^2+O(t^3))
> }}}
What if
{{{
f = SR(1+2^x)
}}}
or something worse (including e.g. exp, log, sin, ... or other functions)?
There are no parents (except SR) for any of these constructs.
--
Ticket URL: <http://trac.sagemath.org/ticket/18092#comment:18>
Sage <http://www.sagemath.org>
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