no and yes:
a finite group is not necessarily commutative, I only changed the
CyclicGroup there!
MRING: Yes, we need CommutativeRing !
Am 11.09.15 um 15:07 schrieb Waldek Hebisch:
> Prof. Dr. Johanneas Grabmeier wrote:
>> here a two little improvements/enhancements:
>>
>> I made CyclicGroup of category CommutativeStar and accordingly for
>> MonoidRing, if the Monoid has CommutativeStar, so we can e.g. compute
>> the determinant of a matrix over a group ring of the cyclic group. I
>> also added a function monomialElements as partner of coefficients, which
>> was missing in MonoidRing.
> As Franz wrote we already have 'support'. Concerning categories,
> do you mean the following:
>
> Index: src/algebra/discrgrp.spad
> ===================================================================
> --- src/algebra/discrgrp.spad (revision 1941)
> +++ src/algebra/discrgrp.spad (working copy)
> @@ -10,7 +10,7 @@
> ++ References:
> ++ Description:
> ++ The category of finite groups.
> -FiniteGroup : Category == Join(Group, Finite) with
> +FiniteGroup : Category == Join(Group, CommutativeStar, Finite) with
> order : % -> Integer
> ++ \spad{order(x)} computes the order of the element $x$.
> add -- default
> Index: src/algebra/mring.spad
> ===================================================================
> --- src/algebra/mring.spad (revision 1941)
> +++ src/algebra/mring.spad (working copy)
> @@ -44,6 +44,8 @@
> if R has CharacteristicZero then CharacteristicZero
> if R has CharacteristicNonZero then CharacteristicNonZero
> if R has CommutativeRing then Algebra(R)
> + if R has CommutativeRing and M has CommutativeStar then
> + CommutativeRing
> if (R has Finite and M has Finite) then Finite
> if M has Comparable then
> FreeModuleCategory(R, M)
>
>
> --
> Mit freundlichen Grüßen
>
> Johannes Grabmeier
>
> Prof. Dr. Johannes Grabmeier
> Köckstraße 1, D-94469 Deggendorf
> Tel. +49-(0)-991-2979584, Tel. +49-(0)-151-681-70756
> Tel. +49-(0)-991-3615-141 (d), Fax: +49-(0)-3224-192688
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