	0	pb : 1
	0	wl : 0
	0	wlx : 0
precharge 
	0	_pchg : 0
	10	_bl : 1	[by _pchg:=0]
	20	blst : 0	[by _bl:=1]
	20	_pchg : 1
experimenting... 
time: 20
	20	wlx : 1
event queue:
	30	_bl : X	[from wlx:=1]

expect _bl -> X queued 
time: 24
setting another pull-down rule on to overtake X 
	24	wl : 1
event queue:
	30	_bl : X	[from wlx:=1]
Fanins of node `_bl':
(from [top-level]):
[after 10]	~_pchg:1 -> _bl+:1
[after 10]	wl:1 & pb:1<1><1> -> _bl-:1
[after 10]	wlx:1 & pbx:X<X><1> -> _bl-:1
[after 20, weak]	~blst:0 -> _bl+:1
time: 28
_bl : 1	[by _pchg:=1]
blst : 0	[by _bl:=1]
step: expect pull-down to overtake previous pull down 
WARNING: weak-interference `blst'
>> cause: `_bl' (val: X)
	30	_bl : X	[by wlx:=1]
event queue:
	40	blst : X	[from _bl:=X]
Fanins of node `_bl':
(from [top-level]):
[after 10]	~_pchg:1 -> _bl+:X
[after 10]	wl:1 & pb:1<1><1> -> _bl-:X
[after 10]	wlx:1 & pbx:X<X><1> -> _bl-:X
[after 20, weak]	~blst:0 -> _bl+:X
time: 30
step 
	40	blst : X	[by _bl:=X]
time: 40
