% NOTE : The percent character '%' begins a comment line.


STRUCTURE zero:number 
          succ(pred:number):number.


STRUCTURE empty:list 
          add(head:number,tail:list):list.



% One comment here


STRUCTURE True:boolean 
          False:boolean.

%***********************************************************************
FUNCTION  Plus(x,y:Number):Number; % Another one here
BEGIN
if (y = zero) Then x;  % OK....

if (y != zero) Then succ(plus(x,pred(y)));
END.
%***********************************************************************

STRUCTURE tip:tree node(left:tree,key:number,right:Tree):tree.


%***********************************************************************
FUNCTION Times(x,y:number):number;
BEGIN
if (x = zero) Then zero; 
if (x != zero) Then plus(y,times(pred(x),y));
END.
%***********************************************************************







