resource Stack_User()
  import Stack
  result x, z
  cap Stack  s1, s2
  int  y
  s1 = create Stack(10); s2 = create Stack(20)
  s1.push(4); s1.push(37); s2.push(98)
  if ((x = s1.pop(y)) != OK) { write("error") }
  if ((z = s2.pop(y)) != OK) { write("error") }
end
