#10849: behaviour of gamma strangely sensitive
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Reporter: dsm | Owner: burcin
Type: defect | Status: new
Priority: major | Milestone: sage-4.7.1
Component: symbolics | Keywords:
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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Changes (by burcin):
* milestone: => sage-4.7.1
Comment:
Mike is right and the patch at #10064 resolves this issue.
The side effect is a result of GiNaC's reference counted pointers.
Whenever two expressions compare equal, GiNaC frees the memory of one, and
makes it a pointer to the other. In this example, it replaces `-x - 1/2`
where the coefficient of `x` is in QQ(i), with `-x - 1/2` where the
coefficient is just an `int`.
{{{
sage: t = -x -1/2
sage: t
-x - 1/2
sage: t.operands()
[-x, -1/2]
sage: t.operands()[0]
-x
sage: t.operands()[0].operands()
[x, -1]
sage: t.operands()[0].operands()[1]
-1
sage: t.operands()[0].operands()[1].pyobject()
-1
sage: type(t.operands()[0].operands()[1].pyobject())
<type 'int'>
}}}
Of course there is a chance that this observation changed the result. :)
For `g`, this looks like a different bug:
{{{
sage: g
gamma(-x - 1/2)
sage: g.operands()[0]
-x - 1/2
sage: g.operands()[0].operands()
[x, -1/2]
sage: g.operands()[0].operands()[0]
x
sage: g.operands()[0].operands()[0].operands()
[]
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10849#comment:3>
Sage <http://www.sagemath.org>
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