eja: switch some index orderings to agree with row-then-column semantics.

[sage.d.git] / mjo / eja / eja_algebra.py

diff --git a/mjo/eja/eja_algebra.py b/mjo/eja/eja_algebra.py
index db1494681d054887781efc14acebd2f73653beb0..8fe3a3ceee26f579b7ce9fa126d2169c2a12ec62 100644 (file)
--- a/mjo/eja/eja_algebra.py
+++ b/mjo/eja/eja_algebra.py
@@ -379,6 +379,41 @@ class FiniteDimensionalEuclideanJordanAlgebra(CombinatorialFreeModule):
         return x.trace_inner_product(y)
 
 
+    def multiplication_table(self):
+        """
+        Return a readable matrix representation of this algebra's
+        multiplication table. The (i,j)th entry in the matrix contains
+        the product of the ith basis element with the jth.
+
+        This is not extraordinarily useful, but it overrides a superclass
+        method that would otherwise just crash and complain about the
+        algebra being infinite.
+
+        SETUP::
+
+            sage: from mjo.eja.eja_algebra import (JordanSpinEJA,
+            ....:                                  RealCartesianProductEJA)
+
+        EXAMPLES::
+
+            sage: J = RealCartesianProductEJA(3)
+            sage: J.multiplication_table()
+            [e0  0  0]
+            [ 0 e1  0]
+            [ 0  0 e2]
+
+        ::
+
+            sage: J = JordanSpinEJA(3)
+            sage: J.multiplication_table()
+            [e0 e1 e2]
+            [e1 e0  0]
+            [e2  0 e0]
+
+        """
+        return matrix(self._multiplication_table)
+
+
     def natural_basis(self):
         """
         Return a more-natural representation of this algebra's basis.
@@ -603,8 +638,8 @@ class RealCartesianProductEJA(FiniteDimensionalEuclideanJordanAlgebra):
     """
     def __init__(self, n, field=QQ):
         V = VectorSpace(field, n)
-        mult_table = [ [ V.basis()[i]*(i == j) for i in range(n) ]
-                       for j in range(n) ]
+        mult_table = [ [ V.basis()[i]*(i == j) for j in range(n) ]
+                       for i in range(n) ]
 
         fdeja = super(RealCartesianProductEJA, self)
         return fdeja.__init__(field, mult_table, rank=n)
@@ -791,7 +826,7 @@ def _multiplication_table_from_matrix_basis(basis):
     V = VectorSpace(field, dimension**2)
     W = V.span_of_basis( _mat2vec(s) for s in basis )
     n = len(basis)
-    mult_table = [[W.zero() for i in range(n)] for j in range(n)]
+    mult_table = [[W.zero() for j in range(n)] for i in range(n)]
     for i in range(n):
         for j in range(n):
             mat_entry = (basis[i]*basis[j] + basis[j]*basis[i])/2
@@ -1257,7 +1292,7 @@ class JordanSpinEJA(FiniteDimensionalEuclideanJordanAlgebra):
     """
     def __init__(self, n, field=QQ):
         V = VectorSpace(field, n)
-        mult_table = [[V.zero() for i in range(n)] for j in range(n)]
+        mult_table = [[V.zero() for j in range(n)] for i in range(n)]
         for i in range(n):
             for j in range(n):
                 x = V.basis()[i]