( ( stack
  =   (S=)
      (push=.(!arg.!(its.S)):?(its.S))
      ( pop
      = top.!(its.S):(%?top.?(its.S))&!top
      )
      (top=top.!(its.S):(%?top.?)&!top)
      (empty=.!(its.S):)
  )
& new$stack:?Stack
& (Stack..push)$(2*a)
& (Stack..push)$pi
& (Stack..push)$
& (Stack..push)$"to be or"
& (Stack..push)$"not to be"
& out$((Stack..pop)$|"Cannot pop (a)")
& out$((Stack..top)$|"Cannot pop (b)")
& out$((Stack..pop)$|"Cannot pop (c)")
& out$((Stack..pop)$|"Cannot pop (d)")
& out$((Stack..pop)$|"Cannot pop (e)")
& out$((Stack..pop)$|"Cannot pop (f)")
& out$((Stack..pop)$|"Cannot pop (g)")
& out$((Stack..pop)$|"Cannot pop (h)")
&   out
  $ ( str
    $ ( "Stack is "
        ((Stack..empty)$&|not)
        " empty"
      )
    )
&
);