#9138: Categories for all rings
---------------------------------+------------------------------------------
Reporter: jbandlow | Owner: nthiery
Type: defect | Status: needs_work
Priority: major | Milestone: sage-4.7.1
Component: categories | Keywords: introspection, categories
for rings
Work_issues: Steenrod algebras | Upstream: N/A
Reviewer: | Author: Simon King
Merged: | Dependencies: sage-4.7, #11268, #11139,
#9976, #9944, #11269
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Comment(by SimonKing):
It seems that the problem is deeper. With the first patch, I obtain
{{{
sage: A1 = SteenrodAlgebra(profile=[2,1])
sage: A1.coerce_map_from(ZZ)
Conversion map:
From: Integer Ring
To: sub-Hopf algebra of mod 2 Steenrod algebra, milnor basis, profile
function [2, 1]
}}}
Without the patch, I obtain
{{{
sage: A1 = SteenrodAlgebra(profile=[2,1])
sage: A1.coerce_map_from(ZZ)
Composite map:
From: Integer Ring
To: sub-Hopf algebra of mod 2 Steenrod algebra, milnor basis, profile
function [2, 1]
Defn: Natural morphism:
From: Integer Ring
To: Finite Field of size 2
then
Generic morphism:
From: Finite Field of size 2
To: sub-Hopf algebra of mod 2 Steenrod algebra, milnor basis,
profile function [2, 1]
}}}
By consequence, when doing `A1(3)` with my patch, a direct conversion is
attempted from `ZZ` to `A1`, but the auxiliary methods involved in the
conversion assume that the argument 3 has already been converted into the
base ring, `GF(2)`.
Perhaps a "register_coercion" during initialisation could help.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9138#comment:71>
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