Hi
On 21.02.2015 22:13, Nils Bruin wrote:
On Saturday, February 21, 2015 at 12:57:44 PM UTC-8, Simon King wrote:
I.e., if P is a commutative additive group, then P.coerce_map_from(ZZ)
should return a morphism in the category of commutative additive
groups.
Then, x+0 should work (because the coercion map is a morphism in the
category of additive groups), but x*0 should not work (because it is
not
a morphism of multiplicative groups).
I'm not so sure. How does x+3 make unambiguous sense? We can map ZZ onto
any cyclic subgroup. There is not necessarily a unique maximal one (for
x+0 it obviously doesn't matter which one we choose, though)
x+3 makes no sense. I was trying to argue that x+0 makes sense. But
I guess it works against the way the coercion model is set up. So I will
just have to deal with "+0" and "sum()" issues I guess.
Thanks to both of you and Simon for the clarifications.
So I will consider the issue closed/answered.
Best
Jonas
P.S. in sage.modular.modform_hecketriangle I implemented both, the ring
of modular forms and the vector spaces (homogeneous parts of the graded
ring). Note in particular that I implemented it in such a way that
multiplication of module elements give again module elements (in a
different space). Check it ouf if you're interested.
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