MODULE UseStack; (* use the StackOfInteger module *)
   IMPORT Out, SI := StackOfInteger; (* imports StackOfInteger under the name "SI" *)

   VAR    st     : SI.Stack;
          v, sum : INTEGER;

BEGIN

   st := SI.newStack();                           (* create a stack *)

   SI.push( st,   1 );                            (* add some items *)
   SI.push( st,  23 );
   SI.push( st, 456 );

   WHILE ~ SI.empty( st ) DO    (* unstack, sum and print the items *)
      v := SI.pop( st );
      INC( sum, v );
      Out.Int( v, 0 );
      IF ~ SI.empty( st ) THEN
         Out.String( " (" );Out.Int( SI.peek( st ), 0 );Out.String( ")" )
      END;
      Out.Ln
   END;
   Out.String( "sum: " );Out.Int( sum, 0 );Out.Ln

END UseStack.