#13221: Limit should not depend on dummy variable.
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Reporter: kcrisman | Owner: burcin
Type: defect | Status: needs_work
Priority: minor | Milestone: sage-pending
Component: calculus | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Changes (by nbruin):
* status: needs_review => needs_work
* milestone: sage-duplicate/invalid/wontfix => sage-pending
Comment:
I do get the reported behaviour in 6.5beta
{{{
sage: f(x) = x^2
sage: limit(f,x=1)
x |--> 1
}}}
This is coming from the fact that sage does this transformation (well,
it's a side-effect of the implementation above):
{{{
limit( E.function(t), t=1) ---> E.limit(t=1).function(t)
}}}
That transformation really has no merit whatsoever. The thing that's hard
about this is that the type of `E.function(t)` is just
`SymbolicExpression`. The callable bit is entirely stored in the parent.
Another way would be to subclass to CallableSymbolicExpression and
override things like `limit` and `integral` to produce errors instead (or
do something useful if there is a reasonable choice).
Arithmetic on callable expressions in general seems pretty sane:
{{{
sage: f(x)=x^2
sage: g(y)=1+y
sage: f+g
(x, y) |--> x^2 + y + 1
}}}
--
Ticket URL: <http://trac.sagemath.org/ticket/13221#comment:9>
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