eja: fix cartesian_factors() for EJA elements.

diff --git a/mjo/eja/TODO b/mjo/eja/TODO
index 38cff88c1584b5be8c6a6ce7e90a47b8350adce3..421e0e9450bd18bab8fc5b9f0c75c738df099080 100644 (file)
--- a/mjo/eja/TODO
+++ b/mjo/eja/TODO
@@ -6,3 +6,5 @@
    could easily cache the identity and charpoly coefficients using
    the nontrivial factor. On the other hand, it's nice that we can
    test out some alternate code paths...
    could easily cache the identity and charpoly coefficients using
    the nontrivial factor. On the other hand, it's nice that we can
    test out some alternate code paths...

+
+4. Conjecture: if x = (x1,x2), then det(x) = det(x1)det(x2).

diff --git a/mjo/eja/eja_algebra.py b/mjo/eja/eja_algebra.py
index d02b55836c3b47608120f9d72f5cab91d2d04ed4..907f40d72135df42d211cdd9bb8923df6bf462e6 100644 (file)
--- a/mjo/eja/eja_algebra.py
+++ b/mjo/eja/eja_algebra.py
@@ -3192,6 +3192,34 @@ class CartesianProductEJA(FiniteDimensionalEJA):
         ones = tuple(J.one().to_matrix() for J in factors)
         self.one.set_cache(self(ones))
 
         ones = tuple(J.one().to_matrix() for J in factors)
         self.one.set_cache(self(ones))
 

+    def _sets_keys(self):
+        r"""
+
+        SETUP::
+
+            sage: from mjo.eja.eja_algebra import (ComplexHermitianEJA,
+            ....:                                  RealSymmetricEJA)
+
+        TESTS:
+
+        The superclass uses ``_sets_keys()`` to implement its
+        ``cartesian_factors()`` method::
+
+            sage: J1 = RealSymmetricEJA(2,
+            ....:                       field=QQ,
+            ....:                       orthonormalize=False,
+            ....:                       prefix="a")
+            sage: J2 = ComplexHermitianEJA(2,field=QQ,orthonormalize=False)
+            sage: J = cartesian_product([J1,J2])
+            sage: x = sum(i*J.gens()[i] for i in range(len(J.gens())))
+            sage: x.cartesian_factors()
+            (a1 + 2*a2, 3*b0 + 4*b1 + 5*b2 + 6*b3)
+
+        """
+        # Copy/pasted from CombinatorialFreeModule_CartesianProduct,
+        # but returning a tuple instead of a list.
+        return tuple(range(len(self.cartesian_factors())))
+

     def cartesian_factors(self):
         # Copy/pasted from CombinatorialFreeModule_CartesianProduct.
         return self._sets
     def cartesian_factors(self):
         # Copy/pasted from CombinatorialFreeModule_CartesianProduct.
         return self._sets