Fanins of node `t':
(from [top-level]):
[after 10, weak]	~f -> t+
[after 10, weak]	f -> t-
Fanins of node `f':
(from [top-level]):
[after 10, weak]	~t -> f+
[after 10, weak]	t -> f-
setting X -> 1 
	0	t : 1
	10	f : 0	[by t:=1]
setting 1 -> 0 
	10	t : 0
	20	f : 1	[by t:=0]
setting 0 -> X 
WARNING: weak-interference `f'
>> cause: `t' (val: X)
	20	t : X
	30	f : X	[by t:=X]
setting X -> 0 
	30	t : 0
	40	f : 1	[by t:=0]
setting 0 -> 1 
	40	t : 1
	50	f : 0	[by t:=1]
setting 1 -> X 
WARNING: weak-interference `f'
>> cause: `t' (val: X)
	50	t : X
	60	f : X	[by t:=X]
how did we do? 
TODO: the interference warnings do not exactly match those of 
the non-weak version of this test! 
