Opened 4 years ago

Closed 3 years ago

#20455 closed defect (invalid)

rewrite buggy Expression.coefficients() without Maxima

Reported by: rws Owned by:
Priority: major Milestone: sage-duplicate/invalid/wontfix
Component: symbolics Keywords:
Cc: paulmasson Merged in:
Authors: Reviewers:
Report Upstream: N/A Work issues:
Branch: Commit:
Dependencies: Stopgaps:

Description

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).

Change History (6)

comment:1 Changed 3 years ago by rws

For implementation reasons the rewrite happened in #21034 but the behaviour was not changed so this ticket still has to be addressed.

comment:2 Changed 3 years ago by paulmasson

  • Cc paulmasson added

comment:3 Changed 3 years ago by rws

This is fixed in current Pynac master.

comment:4 Changed 3 years ago by rws

  • Milestone changed from sage-7.2 to sage-duplicate/invalid/wontfix
  • Status changed from new to needs_review

Since #21369 contains doctests for this, it can be closed.

comment:5 Changed 3 years ago by rws

  • Status changed from needs_review to positive_review

comment:6 Changed 3 years ago by vbraun

  • Resolution set to invalid
  • Status changed from positive_review to closed
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