#15303: Coercion discovery fails to be transitive
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Reporter: nbruin | Owner:
Type: defect | Status: needs_review
Priority: major | Milestone: sage-6.0
Component: coercion | Resolution:
Keywords: | Merged in:
Authors: Simon King | Reviewers:
Report Upstream: N/A | Work issues: Crash in permgroup.py
Branch: | Commit:
u/SimonKing/ticket/15303 | 528a03535447d67f04dc16d0a22cc38def54f9f1
Dependencies: #14711, #15329, | Stopgaps:
#15331 |
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Comment (by nbruin):
Replying to [comment:99 jdemeyer]:
> {{{
> sage: ZZ(CC(1))
> ...
> /usr/local/src/sage-5.13.beta1/local/lib/python2.7/site-
packages/sage/rings/integer.so in sage.rings.integer.Integer.__init__
(sage/rings/integer.c:7889)()
>
> TypeError: unable to coerce <type
'sage.rings.complex_number.ComplexNumber'> to an integer
> sage: ZZ(RR(CC(1)))
> 1
> }}}
I don't think it necessarily is related: this is a conversion and given
how liberal conversion is allowed/meant to be, I don't think we can expect
convertibility to ever be transitive (I think it will even be path-
dependent). As the trace shows, it fails in
`sage.rings.integer.Integer.__init__`, i.e., just the integer constructor.
I suspect RR has been special-cased there and CC is not (perhaps it
should). So, the initializer attempts to see if straight coercion works
and of course it doesn't.
I don't think these conversions are going to be terribly useful anyway:
{{{
sage: ZZ(49*RR(1/49))
TypeError: Attempt to coerce non-integral RealNumber to Integer
}}}
}}}
--
Ticket URL: <http://trac.sagemath.org/ticket/15303#comment:100>
Sage <http://www.sagemath.org>
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