#19813: VectorSpace basis() is mutable
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Reporter: mjo | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-7.0
Component: linear algebra | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Comment (by nbruin):
No, this is indeed quite a bad bug, since VectorSpaces are
UniqueRepresentation:
{{{
sage: V=VectorSpace(QQ,3)
sage: W=VectorSpace(QQ,3)
sage: b=V.basis()
sage: b+="a"
sage: len(W.basis())
4
}}}
Note that V and W are (to the user) obtained independently, so a change on
one should not affect the other.
Also note that some effort is undertaken to make the thing immutable:
{{{
sage: b.append("a")
ValueError: object is immutable; please change a copy instead.
sage: type(b)
<class 'sage.structure.sequence.Sequence_generic'>
sage: b.is_mutable()
False
sage: type(b).__iadd__
<slot wrapper '__iadd__' of 'list' objects>
}}}
So it seems we just failed to shadow the "__iadd__" method.
--
Ticket URL: <http://trac.sagemath.org/ticket/19813#comment:2>
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