node (+)(x,y:int) returns (z:int)
let
  automaton
    state Up
      do z = x + y;
      until z > 10 then Down
    state Down
      do z = x - y;
      until z < -10 then Up
  end
tel


node updown'() returns (y:int)
let
  y = (0 fby y) + 1
tel

node main() returns (y:int)
let
  y = updown'();
tel