#lang racket

;; Thanks for Michael Ballantyne for translating the lecture example to Racket

(module m1 racket
 (provide (contract-out [double (-> (-> integer? integer?) integer?)]))
 (define (double f)
   (f (f 0))))

(module m2 racket
 (provide (contract-out [pos (-> integer? boolean?)]))
 (define (pos i)
   (if (< i 0) #f #t)))

(module m3 racket
 (require (submod ".." m1) (submod ".." m2))
 (double pos))

(require 'm3)