eja: define the trace of an element in a trivial algebra.

diff --git a/mjo/eja/eja_element.py b/mjo/eja/eja_element.py
index 2eb267727235946ed94681d973c915407c5d3dc1..bd45b179541487bd82e3b06768a902a77cd0899d 100644 (file)
--- a/mjo/eja/eja_element.py
+++ b/mjo/eja/eja_element.py
@@ -1248,6 +1248,12 @@ class FiniteDimensionalEuclideanJordanAlgebraElement(IndexedFreeModuleElement):
         """
         P = self.parent()
         r = P.rank()
+
+        if r == 0:
+            # Special case for the trivial algebra where
+            # the trace is an empty sum.
+            return P.base_ring().zero()
+
         p = P._charpoly_coeff(r-1)
         # The _charpoly_coeff function already adds the factor of
         # -1 to ensure that _charpoly_coeff(r-1) is really what