title: Racket: contracts on higher-order functions
body: <p>I am using Racket contract system, and I want to export a function of no arguments, which returns a lambda expression with no arguments, e. g.:</p>
  
  <pre><code>#lang racket
  (define (foo)
    (do-somthing)
    (lambda ()
      (do-other things)))
  </code></pre>
  
  <p>Does anyone know how to write contract for this kind of function?</p>