bug comparing trivial dirichlet characters

[Jonathan Bober]

Hi all,

I just came across a small but annoying bug ( http://trac.sagemath.org/sage_trac/ticket/12632 ). Is it easy for someone to figure out what is going wrong here? It is some problem with coercion, I think, and I think that it may take me a long time to figure out exactly what is going wrong, so I'm hoping someone else can figure it out easily.

Copy and paste from the trac ticket:

{{{

sage: G1 = DirichletGroup(4)

sage: G2 = DirichletGroup(1)

sage: G2[0] == G1[0].primitive_character()

[...]

ZeroDivisionError: Inverse does not exist.

}}}

(The answer should be {{{True}}}.)

What happens, I think, is that {{{G1[0].primitive_character().parent().base_ring()}}} is not the same as {{{G2.base_ring()}}} and something somewhere tries to do some coercion, and fails:

{{{

sage: G1[0].primitive_character().parent().base_ring()

Cyclotomic Field of order 2 and degree 1

sage: G2.base_ring()

Cyclotomic Field of order 1 and degree 1

}}}

[daveloeffler]

On Tuesday, 6 March 2012 01:59:18 UTC, Jonathan Bober wrote:

Hi all,

I just came across a small but annoying bug ( http://trac.sagemath.org/sage_trac/ticket/12632 ). Is it easy for someone to figure out what is going wrong here? It is some problem with coercion, I think, and I think that it may take me a long time to figure out exactly what is going wrong, so I'm hoping someone else can figure it out easily.

Yup, this is a bug in the coercion code for cyclotomic fields. Patch is up on trac.

David

[Jonathan Bober]

Nice! Expect a positive review shortly...

Thanks.

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