>> f = function [private count = 0] x -> y this.count = this.count + 1; ... end >> f.count 0 >> f(1); >> f.count 1 >> f(2); >> f.count 3 >> f.count = 0; // !!! error ...Inside the function body, to access a private parameter, this keyword must be used. Internal parameters will add to the implicit behavior of a function, and makes the function call results hard to predict, therefore they should be used only when necessary.