#17701: diff(f,t) should work even with Function objects
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Reporter: rws | Owner:
Type: defect | Status: needs_review
Priority: major | Milestone: sage-7.2
Component: calculus | Resolution:
Keywords: | Merged in:
Authors: Ralf Stephan | Reviewers: Travis Scrimshaw
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/rws/diff_f_t__should_work_even_with_function_objects|
0cecec3ff4c53e8e030311b4b55fc9e7d96a8cda
Dependencies: | Stopgaps:
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Comment (by nbruin):
Replying to [comment:9 tscrim]:
> Should we expect this to work?
> {{{
> sage: f = function('f')
> sage: diff(f, x=x)
> }}}
I'd say no. This would be significant feature creep into the interface of
`diff`.
I am a little worried about
{{{
sage: diff(f,x,x)
D[0, 0](f)(x, x) + 2*D[0, 1](f)(x, x) + D[1, 1](f)(x, x)
}}}
where almost certainly a user who would type this would be hoping for
{{{
D[0, 0](f)(x)
}}}
I think the ambiguity in meaning when multiple arguments are given makes
it safer to disallow it altogether.
I wouldn't mind if we wouldn't support this at all, but if we do, I
recommend that we only allow repetition of a single argument variable, and
interpret it as the n-th derivative of a univariate function evaluated at
that argument
--
Ticket URL: <http://trac.sagemath.org/ticket/17701#comment:10>
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