node aux (i: int) returns (a, b: int);
let
  a = 1 -> pre i;
  b = 2 * i -> (3 * pre i);
tel

node n (i: int) returns (o1, o2: int);
var u1, u2, t1, t2: int; c: bool;
let
  c = true -> not pre c;
  (t1, t2) = aux (i) when c;
  (u1, u2) = aux (i) when (not c);
  o1 = merge c t1 u1;
  o2 = merge c t2 u2;
tel