% define a Rectangle "class"
var int: Rectangle(var int: width, var int: height) =
  let {
    var int: this;
    constraint Type(this) = Rectangle; %define the "type" of the instance
    %define some "instance methods"
    constraint area(this) = width*height;
    constraint width(this) = width;
    constraint height(this) = height;
  } in this;

%this enum should contain the list of class names
enum Type = {Rectangle};
function var Type: Type(var int:a);

%declare the "instance methods"
function var int: area(var int:this) = let {var int:result;} in result;
function var int: height(var int:a) = let {var int:result;} in result;
function var int: width(var int:a) = let {var int:result;} in result;

%create an instance of the "class"
var int: rect = Rectangle(3,4);
var int: area1 = area(rect);

solve satisfy;

% print the area of the rectangle
output [show(area1),"\n"];