#20455: rewrite buggy Expression.coefficients() without Maxima
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Reporter: rws | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-7.2
Component: symbolics | Keywords:
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
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At the moment the `ex1.coefficients(ex2)` method uses pexpect-Maxima to
get a coefficient list of a symbolic expression `ex1` when seen as a
polynomial in `ex2` but the list is wrong whenever the exponent of `ex2`
is nonnumeric:
{{{
sage: var('a, x')
(a, x)
sage: f = a*x - x^x
sage: f.coefficient(x^x)
-1
sage: f.coefficients(x)
[[-x^x, 0], [a, 1]]
}}}
It should not be difficult to rewrite `coefficients` using wildcard power
search and the `coefficient` method (which doesn't use Maxima).
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Ticket URL: <http://trac.sagemath.org/ticket/20455>
Sage <http://www.sagemath.org>
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