#13125: Reals sets consisting of intervals and isolated points
-------------------------------------+-------------------------------------
Reporter: ares | Owner: Ares Ribó
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.2
Component: calculus | Resolution:
Keywords: | Merged in:
Authors: Volker Braun , | Reviewers: Ralf Stephan
Jordi Saludes , Ares Ribó | Work issues:
Report Upstream: N/A | Commit:
Branch: | fa497ee701f068e3980e458a519805b219b1b791
u/vbraun/ticket/13125 | Stopgaps:
Dependencies: |
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Comment (by tscrim):
I don't like this change:
{{{#!diff
+ elif isinstance(x,
sage.rings.real_mpfi.RealIntervalFieldElement):
+ if x.upper().is_infinity() or x.lower().is_infinity():
return self.gen()
}}}
since `RIF(0, oo)` gets turned into infinity (where is very likely to not
be):
{{{
sage: UnsignedInfinityRing(RIF(2, oo))
Infinity
}}}
I think we should follow the usual paradigm for RIF:
{{{
sage: RIF(2, 4) == 4
False
sage: RIF(2, 4) <= 4
True
sage: RIF(2, 4) < 4
False
sage: RIF(2) == 2
True
}}}
So I would say this is wrong:
{{{
sage: RIF(2, oo) == oo
True
}}}
and I would raise an error anytime we're converting something which is not
directly equal to a (signed) infinity. For example:
{{{
sage: UnsignedInfinityRing(RIF(2, oo))
Infinity
}}}
should raise an error, but this would be okay:
{{{
sage: UnsignedInfinityRing(RIF(oo, oo))
Infinity
}}}
--
Ticket URL: <http://trac.sagemath.org/ticket/13125#comment:38>
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