#17984: Dedicated RR.__contains__() and CC.__contains__()
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Reporter: rws | Owner:
Type: | Status: needs_review
enhancement | Milestone: sage-6.6
Priority: major | Resolution:
Component: basic | Merged in:
arithmetic | Reviewers:
Keywords: | Work issues:
Authors: Ralf | Commit:
Stephan | 544450ea18ed2778953141bab8feced61237556e
Report Upstream: N/A | Stopgaps:
Branch: |
u/rws/17984 |
Dependencies: |
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Comment (by rws):
Replying to [comment:20 pbruin]:
> Hence I am tending towards the opinion that if `x` is some exact
element, then `bool(RR(x) == x)` should return `True` if and only if `x`
is exactly representable in `RR`.
Can you please help me with this definition? In my understanding an exact
representation has infinite precision (or another bit of information that
makes it different from an inexact element). But everything in `RR` has
finite `precision()`, even `oo` and `NaN` which by definition are special.
So, either no integers and rationals are `in RR`, or `RR` elements must
carry an exact flag that is set to `False` when an operation with an
inexact element is performed, or, most probably, I'm missing something
about how to spot elements with exact representation in `RR/CC`. I cannot
imagine you would mean `1` is exactly representable in `RR` because `1 ==
RR(1)`, since that would obviously be circular with your definition.
--
Ticket URL: <http://trac.sagemath.org/ticket/17984#comment:24>
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