On Jan 18, 7:30 pm, "D. M. Monarres" <dmmonar...@gmail.com> wrote:
> Hello all,
>
> Running into an issue with something. I must be missing something. Say I
> construct two groups that I know are isomorphic.
>
> sage: G = SymmetricGroup(5)
> sage: r = G('(1,2,5,4,3)')
> sage: s = G('(1,5),(3,4)')
> sage: H = G.subgroup([r,s])
> sage: H
> Subgroup of SymmetricGroup(5) generated by [(1,2,5,4,3), (1,5)(3,4)]
> sage: D = DihedralGroup(5)
> sage: D
> Dihedral group of order 10 as a permutation group
>
> I get an TypeError when I try and construct a homomorphism between these two
> groups.
> sage: phi = D.hom( ['(1,2,5,4,3)', '(1,5)(3,4)'] , H)
> ---------------------------------------------------------------------------
> TypeError Traceback (most recent call last)
>
> /Users/ayeq/Dropbox/src/sdsu-sage-tutorial/<ipython console> in <module>()
>
> /Users/ayeq/sage/local/lib/python2.6/site-packages/sage/structure/parent_ge
> ns.so
> in sage.structure.parent_gens.ParentWithGens.hom
> (sage/structure/parent_gens.c:3858)()
>
> /Users/ayeq/sage/local/lib/python2.6/site-packages/sage/categories/homset.p yc
> in __call__(self, x, y, check, on_basis)
> 432 return self.element_class_set_morphism(self, x)
> 433
> --> 434 raise TypeError, "Unable to coerce x (=%s) to a morphism in
> %s"%(x,self)
> 435
> 436 @lazy_attribute
>
> TypeError: Unable to coerce x (=['(1,2,5,4,3)', '(1,5)(3,4)']) to a morphism
> in Set of Morphisms from Dihedral group of order 10 as a permutation group
> to Subgroup of SymmetricGroup(5) generated by [(1,2,5,4,3), (1,5)(3,4)] in
> Category of finite permutation groups
>
> I have tried to do this in a few different ways. (by coercing the elements
> first, etc...) Can somebody see what I am missing? Thank you in advance.
This looks like a bug to me, but I'm not sure. Anyway, you can do
this:
sage: PermutationGroupMorphism(D, H, D.gens(), H.gens())
Homomorphism : Dihedral group of order 10 as a permutation group -->
Subgroup of SymmetricGroup(5) generated by [(1,2,5,4,3), (1,5)(3,4)]
(I don't know why "D.hom(H.gens(), H)" doesn't do the same thing...)
--
John
--
To post to this group, send email to sage-support@googlegroups.com
To unsubscribe from this group, send email to
sage-support+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/sage-support
URL: http://www.sagemath.org
