X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;ds=sidebyside;f=mjo%2Feja%2Feja_algebra.py;h=ec692e4f93b8f015f8813eb2653e70a053b66dff;hb=452398e489e1e45cd06ce010878eeb07c3e72dd5;hp=8ca501d6ba944a539901d384a78a5c8a0f45a7ca;hpb=3f8818f3eca0b2ea388130ff805875012cf902cb;p=sage.d.git

diff --git a/mjo/eja/eja_algebra.py b/mjo/eja/eja_algebra.py
index 8ca501d..ec692e4 100644
--- a/mjo/eja/eja_algebra.py
+++ b/mjo/eja/eja_algebra.py
@@ -2111,6 +2111,20 @@ class BilinearFormEJA(RationalBasisEuclideanJordanAlgebra):
         sage: J0.multiplication_table() == J0.multiplication_table()
         True
 
+    An error is raised if the matrix `B` does not correspond to a
+    positive-definite bilinear form::
+
+        sage: B = matrix.random(QQ,2,3)
+        sage: J = BilinearFormEJA(B)
+        Traceback (most recent call last):
+        ...
+        ValueError: bilinear form is not positive-definite
+        sage: B = matrix.zero(QQ,3)
+        sage: J = BilinearFormEJA(B)
+        Traceback (most recent call last):
+        ...
+        ValueError: bilinear form is not positive-definite
+
     TESTS:
 
     We can create a zero-dimensional algebra::
@@ -2151,7 +2165,7 @@ class BilinearFormEJA(RationalBasisEuclideanJordanAlgebra):
         n = B.nrows()
 
         if not B.is_positive_definite():
-            raise TypeError("matrix B is not positive-definite")
+            raise ValueError("bilinear form is not positive-definite")
 
         V = VectorSpace(field, n)
         mult_table = [[V.zero() for j in range(n)] for i in range(n)]
@@ -2187,9 +2201,8 @@ class BilinearFormEJA(RationalBasisEuclideanJordanAlgebra):
         Return a random instance of this algebra.
         """
         n = ZZ.random_element(cls._max_random_instance_size() + 1)
-        if n == 0:
-            # Special case needed since we use (n-1) below.
-            B = matrix.identity(field, 0)
+        if n.is_zero():
+            B = matrix.identity(field, n)
             return cls(B, field, **kwargs)
 
         B11 = matrix.identity(field,1)
@@ -2292,6 +2305,16 @@ class JordanSpinEJA(BilinearFormEJA):
         B = matrix.identity(field, n)
         super(JordanSpinEJA, self).__init__(B, field, **kwargs)
 
+    @classmethod
+    def random_instance(cls, field=AA, **kwargs):
+        """
+        Return a random instance of this type of algebra.
+
+        Needed here to override the implementation for ``BilinearFormEJA``.
+        """
+        n = ZZ.random_element(cls._max_random_instance_size() + 1)
+        return cls(n, field, **kwargs)
+
 
 class TrivialEJA(FiniteDimensionalEuclideanJordanAlgebra):
     """