initializing
system : app(f, app(s, x[1])) -> app(f, app(app(g, x[1]), x[1]))
system : app(app(g, 0), 1) -> app(s, 0)
system : 0 -> 1
system : app(app(map, fun[3]), nil) -> nil
system : app(app(map, fun[3]), app(app(cons, x[1]), xs[2])) -> app(app(cons, app(fun[3], x[1])), app(app(map, fun[3]), xs[2]))
system : app(app(filter, fun[3]), nil) -> nil
system : app(app(filter, fun[3]), app(app(cons, x[1]), xs[2])) -> app(app(app(app(filter2, app(fun[3], x[1])), fun[3]), x[1]), xs[2])
system : app(app(app(app(filter2, true), fun[3]), x[1]), xs[2]) -> app(app(cons, x[1]), app(app(filter, fun[3]), xs[2]))
system : app(app(app(app(filter2, false), fun[3]), x[1]), xs[2]) -> app(app(filter, fun[3]), xs[2])
ds : 0
ds : app