README text here.
- https://felleisen.org/matthias/Thoughts/Racket_is____.html
- https://docs.racket-lang.org/guide/module-languages.html#%28tech._module._language%29
- https://news.ycombinator.com/from?site=programming-puzzler.blogspot.com
(@ "Adds 1 to the given number")
(: Nat -> Nat)
(def (add1 n)
(+ n 1))
(examples add1
[0 1]
[-1 error]
[15 16])