(type (Pair a b)
  (Pair a b))

(define (start _)
  (display-inline (str-append "Hello, world!" "\n")))

(define (str-append s1 s2) (-str-append (Pair s1 s2)))

(extern display-inline (Fun Str Unit))
(extern -str-append (Fun (Pair Str Str) Str))