#16422: cancellation of two indefinite limits
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Reporter: dkrenn | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.3
Component: symbolics | Resolution:
Keywords: symbolic, cancellation, | Merged in:
limit, indefinite | Reviewers:
Authors: | Work issues:
Report Upstream: N/A | Commit:
Branch: | Stopgaps:
Dependencies: |
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Comment (by nbruin):
This is an upstream problem (in maxima). It seems "ind" isn't a special
symbol there either:
{{{
Maxima 5.29.1 http://maxima.sourceforge.net
using Lisp ECL 12.12.1
(%i3) limit(sin(x),x,inf)-limit(cos(x),x,inf);
(%o3) 0
}}}
We could intercept ind whenever it comes by (from limit) and raise an
exception to limit the damage, but I imagine the bad simplifications could
already happen internal to maxima.
This seems to happen with infinity as well, by the way:
{{{
(%i14) limit(1/x^2,x,0)-limit(1/x^4,x,0);
(%o14) 0
}}}
Sage catches those (when they happen in a way sage can see it happen), so
perhaps we should recognize `ind` and a special value--leading to an
exception if we can't do anything with it.
--
Ticket URL: <http://trac.sagemath.org/ticket/16422#comment:2>
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