- # Begin with the zero matrix, and add projectors to it if we have any.
- A = V.zero().column()*V.zero().row()
-
- # Careful, begin at idx=1 so that we only generate a projector
- # when rank_A is greater than zero.
- while A.rank() < rank_A:
- v = V.random_element()
- A += v.column()*v.row()
-
- if accept_zero or not A.is_zero():
- # We either don't care what ``A`` is, or it's non-zero, so
- # just return it.
- return A
- else:
- # Uh oh, we need to generate a new one.
- return random_psd(V, accept_zero, rank)
+ if n == 0 and not accept_zero:
+ # We're gonna loop forever trying to satisfy this...
+ raise ValueError('You must have accept_zero=True when V is trivial')
+
+ # Loop until we find a suitable "A" that will then be returned.
+ while True:
+ # Begin with the zero matrix, and add projectors to it if we
+ # have any.
+ A = matrix.zero(V.base_ring(), n, n)
+
+ # Careful, begin at idx=1 so that we only generate a projector
+ # when rank_A is greater than zero.
+ while A.rank() < rank_A:
+ v = V.random_element()
+ A += v.column()*v.row()
+
+ if accept_zero or not A.is_zero():
+ # We either don't care what ``A`` is, or it's non-zero, so
+ # just return it.
+ return A