TESTS:
- The zero element should never be regular::
+ The zero element should never be regular, unless the parent
+ algebra has dimension one::
sage: set_random_seed()
sage: J = random_eja()
- sage: J.zero().is_regular()
- False
+ sage: J.dimension() == 1 or not J.zero().is_regular()
+ True
The unit element isn't regular unless the algebra happens to
consist of only its scalar multiples::