declare
fun {NewStack}
   fun{WrapStack L}
      fun{Push E}
     {WrapStack E|L}
      end

      fun{Pop E}
     case L
     of H|T then
        E=H
        {WrapStack T}
     else error
     end
      end
   in
      stack(push:Push pop:Pop)
   end
in
   {WrapStack nil}
end

S S2 S3 S4 S5
E1 E2 E3

S = {NewStack}
S2 = {{{S.push 4}.push 7}.push 9}

{Browse S2}

S3 = {S2.pop E1}
S4 = {S3.pop E2}
S5 = {S4.pop E3}

{Browse E1#E2#E3}