From: Michael Orlitzky <michael@orlitzky.com>
Date: Sun, 28 Jul 2019 15:21:00 +0000 (-0400)
Subject: eja: use FreeModules() category for operators instead of VectorSpaces().
X-Git-Url: https://gitweb.michael.orlitzky.com/?a=commitdiff_plain;h=01ff2cfb39635ad84d8281d58f2d620a18569ff3;p=sage.d.git

eja: use FreeModules() category for operators instead of VectorSpaces().

This allows our characteristic polynomial algorithm to use real
operators and not matrices.
---

diff --git a/mjo/eja/euclidean_jordan_algebra.py b/mjo/eja/euclidean_jordan_algebra.py
index 9072a12..ba2c63c 100644
--- a/mjo/eja/euclidean_jordan_algebra.py
+++ b/mjo/eja/euclidean_jordan_algebra.py
@@ -28,8 +28,11 @@ class FiniteDimensionalEuclideanJordanAlgebraOperator(Map):
 
         # We need to supply something here to avoid getting the
         # default Homset of the parent FiniteDimensionalAlgebra class,
-        # which messes up e.g. equality testing.
-        parent = Hom(domain_eja, codomain_eja, VectorSpaces(F))
+        # which messes up e.g. equality testing. We use FreeModules(F)
+        # instead of VectorSpaces(F) because our characteristic polynomial
+        # algorithm will need to F to be a polynomial ring at some point.
+        # When F is a field, FreeModules(F) returns VectorSpaces(F) anyway.
+        parent = Hom(domain_eja, codomain_eja, FreeModules(F))
 
         # The Map initializer will set our parent to a homset, which
         # is explicitly NOT what we want, because these ain't algebra