#11506: Fix the infinity ring.
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Reporter: vbraun | Owner: AlexGhitza
Type: defect | Status: needs_review
Priority: blocker | Milestone: sage-6.3
Component: algebra | Resolution:
Keywords: | Merged in:
Authors: Volker Braun | Reviewers: Peter Bruin
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/vbraun/infinity_ring | cd9242959af9fda6d5351f8410889b36d6b6a392
Dependencies: 13125 | Stopgaps:
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Comment (by pbruin):
Replying to [comment:20 vbraun]:
> `unsigned_infinity in RR` returns true because there are coercions RR ->
signed infinity ring -> unsigned infinity ring:
Yes, and I think that isn't a problem.
> We could disallow the conversion RR(unsigned_infinity) but it would not
change anything.
Well, if I'm not mistaken, at least it would make `unsigned_infinity in
RR` return False (because the conversion needs to succeed for this to
return True), which was my point.
It seems my last point wasn't very clear, so here an equivalent example
without complex infinities:
{{{
sage: unsigned_infinity + unsigned_infinity
Infinity
sage: unsigned_infinity - unsigned_infinity
...
ValueError: oo - oo not defined
}}}
I think we should raise an error for addition, i.e. make the code of
`_add_()` work in an analogous way to that of `_sub_()`. (Not that this
was caused by your patch; the thing with the `+i` and `-i` just led me to
this inconsistency.)
--
Ticket URL: <http://trac.sagemath.org/ticket/11506#comment:21>
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