#11319: Cannot create homomorphism from prime residue field to finite field
---------------------------+------------------------------------------------
Reporter: johanbosman | Owner: robertwb
Type: defect | Status: needs_work
Priority: major | Milestone: sage-4.7.1
Component: coercion | Keywords: residue fields, finite fields, hom
Work_issues: | Upstream: N/A
Reviewer: | Author: Johan Bosman
Merged: | Dependencies:
---------------------------+------------------------------------------------
Changes (by aly.deines):
* status: needs_review => needs_work
Comment:
I was trying out the patch, and the following example didn't work out like
I expected:
{{{
sage: K
Number Field in a with defining polynomial x^3 - 2
sage: K.<a> = NumberField(x^3-2)
sage: P = K.ideal(7)
sage: P.factor()
Fractional ideal (7)
sage: k = P.residue_field()
sage: k.order()
343
sage: F.<b> = GF(343)
sage: F.order()
343
sage: k
Residue field in abar of Fractional ideal (7)
sage: F
Finite Field in b of size 7^3
sage: k.hom([F(1)])
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
/Users/aly/Desktop/sage-4.7.rc2/<ipython console> in <module>()
/Users/aly/Desktop/sage-4.7.rc2/local/lib/python2.6/site-
packages/sage/structure/parent_gens.so in
sage.structure.parent_gens.ParentWithGens.hom
(sage/structure/parent_gens.c:3792)()
/Users/aly/Desktop/sage-4.7.rc2/local/lib/python2.6/site-
packages/sage/structure/parent.so in sage.structure.parent.Parent.hom
(sage/structure/parent.c:9067)()
/Users/aly/Desktop/sage-4.7.rc2/local/lib/python2.6/site-
packages/sage/rings/finite_rings/homset.pyc in __call__(self, im_gens,
check)
49 return self._coerce_impl(im_gens)
50 except TypeError:
---> 51 raise TypeError, "images do not define a valid
homomorphism"
52
53 def _coerce_impl(self, x):
TypeError: images do not define a valid homomorphism
sage: k.has_coerce_map_from(F)
False
}}}
Should this patch fix this as well?
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11319#comment:3>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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