view tests/specialize.ur @ 316:04ebfe929a98

Unpolyed a polymorphic function of two arguments
author Adam Chlipala <adamc@hcoop.net>
date Thu, 11 Sep 2008 10:14:59 -0400
parents e21d0dddda09
children 6a4e365db60c
line wrap: on
line source
datatype list a = Nil | Cons of a * list a

fun isNil (t ::: Type) (ls : list t) : bool =
        case ls of
          Nil => True
        | Cons _ => False

fun append (t ::: Type) (ls1 : list t) (ls2 : list t) : list t =
        case ls1 of
          Nil => ls2
        | Cons (x, ls1') => Cons (x, append ls1' ls2)

fun delist (ls : list string) : xml body [] [] =
        case ls of
          Nil => <body>Nil</body>
        | Cons (h, t) => <body>{cdata h} :: {delist t}</body>

val ls = Cons ("X", Cons ("Y", Cons ("Z", Nil)))
val ls' = Cons ("A", Cons ("B", Nil))

fun main () : transaction page = return <html><body>
        {if isNil ls then <body>It's Nil.</body> else <body>It's not Nil.</body>}

        <p>{delist (append ls' ls)}</p>
</body></html>