node updown(b : bool) returns (o : bool)
var o2,on_off:bool;
let
  on_off = true;
  automaton
    state Down
      do o2 = false until on_off then Up
    state Up
      do o2 = true until on_off then Down
   end;
   o = merge b (true-> o2) (false -> false)
tel

node main() returns (o:bool)
var b:bool;
let
  b = true fby true fby false fby b;
  o = updown(b);
tel