eja: override _a_regular_element() in subalgebras, since we know one.

diff --git a/mjo/eja/eja_subalgebra.py b/mjo/eja/eja_subalgebra.py
index c82bd1a485c5eb6b82e92134fc30658be4d6d669..e39792a91732724b5fc7bc8b352e8fd977c80940 100644 (file)
--- a/mjo/eja/eja_subalgebra.py
+++ b/mjo/eja/eja_subalgebra.py
@@ -197,6 +197,30 @@ class FiniteDimensionalEuclideanJordanElementSubalgebra(FiniteDimensionalEuclide
                               natural_basis=natural_basis)
 
 
+    def _a_regular_element(self):
+        """
+        Override the superalgebra method to return the one
+        regular element that is sure to exist in this
+        subalgebra, namely the element that generated it.
+
+        SETUP::
+
+            sage: from mjo.eja.eja_algebra import random_eja
+
+        TESTS::
+
+            sage: set_random_seed()
+            sage: J = random_eja().random_element().subalgebra_generated_by()
+            sage: J._a_regular_element().is_regular()
+            True
+
+        """
+        if self.dimension() == 0:
+            return self.zero()
+        else:
+            return self.monomial(1)
+
+
     def _element_constructor_(self, elt):
         """
         Construct an element of this subalgebra from the given one.