node bounds
  (i: int)
returns
  (min: int;
  max: int);

var
  V18_prev_min: int;
  V19_prev_max: int;

let
  min = (if (i < V18_prev_min) then i else V18_prev_min);
  max = (if (i > V19_prev_max) then i else V19_prev_max);
  V18_prev_min = (i -> (pre min));
  V19_prev_max = (i -> (pre max));
tel