eja: allow addition of EJA morphisms.

diff --git a/mjo/eja/euclidean_jordan_algebra.py b/mjo/eja/euclidean_jordan_algebra.py
index 72e167e6811912c3b19a71b27432d052800d3051..b239dc7287326f95815708ca3b80fd2c64d99b1a 100644 (file)
--- a/mjo/eja/euclidean_jordan_algebra.py
+++ b/mjo/eja/euclidean_jordan_algebra.py
@@ -17,7 +17,7 @@ from sage.algebras.finite_dimensional_algebras.finite_dimensional_algebra_morphi
 class FiniteDimensionalEuclideanJordanAlgebraMorphism(FiniteDimensionalAlgebraMorphism):
     """
     A very thin wrapper around FiniteDimensionalAlgebraMorphism that
 class FiniteDimensionalEuclideanJordanAlgebraMorphism(FiniteDimensionalAlgebraMorphism):
     """
     A very thin wrapper around FiniteDimensionalAlgebraMorphism that

-    does only two things:
+    does only three things:

 
       1. Avoids the ``unitary`` and ``check`` arguments to the constructor
          that will always be ``False``. This is necessary because these
 
       1. Avoids the ``unitary`` and ``check`` arguments to the constructor
          that will always be ``False``. This is necessary because these


@@ -28,11 +28,44 @@ class FiniteDimensionalEuclideanJordanAlgebraMorphism(FiniteDimensionalAlgebraMo
       2. Inputs and outputs the underlying matrix with respect to COLUMN
          vectors, unlike the parent class.
 
       2. Inputs and outputs the underlying matrix with respect to COLUMN
          vectors, unlike the parent class.
 

+      3. Allows us to add morphisms in the obvious way.
+

     If this seems a bit heavyweight, it is. I would have been happy to
     use a the ring morphism that underlies the finite-dimensional
     algebra morphism, but they don't seem to be callable on elements of
     If this seems a bit heavyweight, it is. I would have been happy to
     use a the ring morphism that underlies the finite-dimensional
     algebra morphism, but they don't seem to be callable on elements of

-    our EJA.
+    our EJA, and you can't add them.

     """
     """

+
+    def __add__(self, other):
+        """
+        Add two EJA morphisms in the obvious way.
+
+        EXAMPLES:
+
+            sage: J = RealSymmetricEJA(3)
+            sage: x = J.zero()
+            sage: y = J.zero()
+            sage: x.operator() + y.operator()
+            Morphism from Euclidean Jordan algebra of degree 6 over Rational
+            Field to Euclidean Jordan algebra of degree 6 over Rational Field
+            given by matrix
+            [0 0 0 0 0 0]
+            [0 0 0 0 0 0]
+            [0 0 0 0 0 0]
+            [0 0 0 0 0 0]
+            [0 0 0 0 0 0]
+            [0 0 0 0 0 0]
+
+        """
+        P = self.parent()
+        if not other in P:
+            raise ValueError("summands must live in the same space")
+
+        return FiniteDimensionalEuclideanJordanAlgebraMorphism(
+                  P,
+                  self.matrix() + other.matrix() )
+
+

     def __init__(self, parent, f):
         FiniteDimensionalAlgebraMorphism.__init__(self,
                                                   parent,
     def __init__(self, parent, f):
         FiniteDimensionalAlgebraMorphism.__init__(self,
                                                   parent,