;; Define a geometry module with public and private functions
(define module geometry
  (import math)

  ;; Public function - can be used from outside
  (define public square (number -> number)
    (dup *))

  ;; Public function using arithmetic
  (define public cube (number -> number)
    (dup dup * *))

  ;; Private helper function - only visible within module
  (define private double (number -> number)
    (2 *))

  ;; Public function using private helper
  (define public quadruple (number -> number)
    (double double)))