Looks like a bug.

On 2/20/07, Mike Hansen <[EMAIL PROTECTED]> wrote:
>
> Hello,
>
> I've got a quick question about coercion in SAGE.  I'm trying to play
> around with permutation group elements in SAGE.  I run the following
> code, and it behaves exactly as it should.
>
> g1 = PermutationGroupElement([(1,2),(3,4,5)])
> g1.parent()   # => Symmetric group of order 5! as a permutation group
> g2 = PermutationGroupElement([(1,2)])
> g2.parent()   # => Symmetric group of order 2! as a permutation group
> g1*g2  # => (3,4,5)
>
>
> However, when I do 'g2*g1' I get the following error:
>
> <type 'exceptions.RuntimeError'>: There is a bug in the coercion code
> in SAGE.
> Both x (=(1,2)) and y (=None) are supposed to have identical parents
> but they don't.
> In fact, x has parent 'SymmetricGroup(2)'
> whereas y has parent '<type 'NoneType'>'
>
> It seems like this shouldn't be an error and that the correct coercion
> should be done regardless which element comes first.  Is this an
> actual bug or some odd design decision that I'm not aware of?
>
> Thanks,
> Mike
>
>
> >
>

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