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 pairAppend (t1 ::: Type) (t2 ::: Type) (ls1 : list (t1 * t2)) (ls2 : list (t1 * t2)) : list (t1 * t2) = case ls1 of Nil => ls2 | Cons (x, ls1') => Cons (x, pairAppend ls1' ls2) fun delist (ls : list string) : xml body [] [] = case ls of Nil => Nil | Cons (h, t) => {cdata h} :: {delist t} fun pairDelist (ls : list (string * int)) : xml body [] [] = case ls of Nil => Nil | Cons ((s, n), t) => ({cdata s}, {cdata (show _ n)}) :: {pairDelist t} val ls = Cons ("X", Cons ("Y", Cons ("Z", Nil))) val ls' = Cons ("A", Cons ("B", Nil)) val pls = Cons (("X", 1), Cons (("Y", 2), Cons (("Z", 3), Nil))) val pls' = Cons (("A", 1), Cons (("B", 2), Nil)) fun main () : transaction page = return {if isNil ls then It's Nil. else It's not Nil.}

{delist (append ls' ls)}

{pairDelist (pairAppend pls' pls)}