>> circle = class private radius = 1; common getRadius = () -> parent.radius; // access parent.radius is ok here common setRadius = function x -> () if x > 0 parent.radius = x; end end auto perimeter = () -> 2 * pi * parent.radius; auto area = () -> pi * (parent.radius)^2; end >> p = circle.new(); >> p.radius; // Error: accessing private attribute >> p.getRadius() 1 >> p.setRadius(12); >> p.getRadius(); 12Here radius is private attribute and cannot be accessed outside the class. But other attribute functions (getRadius and setRadius) can access it using the parent keyword.