(VAR y z x xs fun)
(RULES
  app(f, app(app(cons, nil), y)) -> y
  app(f, app(app(cons, app(f, app(app(cons, nil), y))), z)) -> app(app(app(copy, n), y), z)
  app(app(app(copy, 0), y), z) -> app(f, z)
  app(app(app(copy, app(s, x)), y), z) -> app(app(app(copy, x), y), app(app(cons, app(f, y)), z))

  app(app(map,fun),nil) -> nil
  app(app(map,fun),app(app(cons,x),xs)) -> app(app(cons,app(fun,x)),app(app(map,fun),xs))

  app(app(filter,fun),nil) -> nil
  app(app(filter,fun),app(app(cons,x),xs)) -> app(app(app(app(filter2,app(fun, x)),fun),x),xs)
  app(app(app(app(filter2,true),fun),x),xs) -> app(app(cons,x),app(app(filter,fun),xs))
  app(app(app(app(filter2,false),fun),x),xs) -> app(app(filter,fun),xs)

)