eja: update the TODO with a bug example.

diff --git a/mjo/eja/TODO b/mjo/eja/TODO
index 5307527b5285eb821f75b8e9dfa58b2d512c10a9..1def3d2e9fd8cf381ae743344ce670a13f226438 100644 (file)
--- a/mjo/eja/TODO
+++ b/mjo/eja/TODO
@@ -8,4 +8,13 @@
        sage: x = random_eja().random_element()
        sage: x.is_invertible() == (x.det() != 0)
 
-   in eja_element.py returns False.
+   in eja_element.py returns False. Example:
+
+       sage: J1 = ComplexHermitianEJA(2)
+       sage: J2 = TrivialEJA()
+       sage: J = cartesian_product([J1,J2])
+       sage: x = J.from_vector(vector(QQ, [-1, -1/2, -1/2, -1/2]))
+       sage: x.is_invertible()
+       True
+       sage: x.det()
+       0