#15021: Return unevaluated derivative
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Reporter: eviatarbach | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-5.12
Component: symbolics | Keywords:
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Dependencies: | Stopgaps:
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There should be a way to return an unevaluated derivative from within the
`_derivative_` or `_tderivative_` method of a `BuiltinFunction`. Perhaps
by returning `None`, like `_eval_` does for remaining unevaluated. As of
now returning `None` causes a segmentation fault.
This is important because for multivariate functions often only the
derivative with respect to one variable may be known, so we want to return
the unevaluated derivative if it's taken with respect to a variable in
which we don't know the derivative. Right now it seems the only way to not
return a derivative is to raise an exception.
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Ticket URL: <http://trac.sagemath.org/ticket/15021>
Sage <http://www.sagemath.org>
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