From: Michael Orlitzky <michael@orlitzky.com>
Date: Fri, 6 Nov 2020 13:44:07 +0000 (-0500)
Subject: eja: document why an a[0] access is safe.
X-Git-Url: http://gitweb.michael.orlitzky.com/?a=commitdiff_plain;h=28ec09b5c64dd7a342a3ae8b35f809cc185d9c63;p=sage.d.git

eja: document why an a[0] access is safe.
---

diff --git a/mjo/eja/eja_algebra.py b/mjo/eja/eja_algebra.py
index 0492946..ded2df6 100644
--- a/mjo/eja/eja_algebra.py
+++ b/mjo/eja/eja_algebra.py
@@ -1006,8 +1006,10 @@ class MatrixEuclideanJordanAlgebra(FiniteDimensionalEuclideanJordanAlgebra):
             # we simply undo the basis_normalizer scaling that we
             # performed earlier.
             #
-            # TODO: make this access safe.
-            XS = a[0].variables()
+            # The a[0] access here is safe because trivial algebras
+            # won't have any basis normalizers and therefore won't
+            # make it to this "else" branch.
+            XS = a[0].parent().gens()
             subs_dict = { XS[i]: self._basis_normalizers[i]*XS[i]
                           for i in range(len(XS)) }
             return tuple( a_i.subs(subs_dict) for a_i in a )