Whoever listens...
On 28 Apr., 22:26, Simon King <simon.k...@nuigalway.ie> wrote:
> Hi!
>
> Let R,S be rings and f:R-->S be a ring homomorphism. If R,S are base
> rings of, e.g., matrix rings or polynomial rings, shouldn't it be
> possible to construct the homomorphism of the "bigger" rings induced
> by f? But how?
Since there was no answer, I guess it isn't implemented yet. Perhaps
it works like this:
def my_map(f,x):
P = parent(x)
try:
return P([f(t) for t in x])
except TypeError:
return P([my_map(f,t) for t in x])
and then I get:
sage: R.<x> = ZZ[]
sage: f = R.hom([2*x],R)
sage: S.<y> = R[]
sage: p = S.random_element()
sage: p
(-x + 3)*y^2 + (-x^2 + x + 12)*y + 2*x^2 + x + 1
sage: my_map(f,p)
(-2*x + 3)*y^2 + (-4*x^2 + 2*x + 12)*y + 8*x^2 + 2*x + 1
and
sage: MS = MatrixSpace(R,2,2)
sage: M = MS.random_element()
sage: M
[9*x^2 + x + 1 -2*x^2 + 6*x]
[ x^2 + x - 17 x^2 - x - 3]
sage: my_map(f,M)
[36*x^2 + 2*x + 1 -8*x^2 + 12*x]
[4*x^2 + 2*x - 17 4*x^2 - 2*x - 3]
Do you think that the above makes sense to implement in the call
method of a new generic class, say, RingHomomorphism_from_basering,
whose instances would be created in S.hom(f,S) and MS.hom(f,MS)? Or
does anybody have a better idea?
Cheers,
Simon
--
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
