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datatype list a = Nil | Cons of a * list a
val isNil = fn t ::: Type => fn ls : list t =>
case ls of Nil => True | _ => False
val show = fn b => if b then "True" else "False"
val rec delist : list string -> xml body [] [] = fn x =>
case x of
Nil => <body>Nil</body>
| Cons (h, t) => <body>{cdata h} :: {delist t}</body>
val main : unit -> page = fn () => <html><body>
{cdata (show (isNil (Nil : list bool)))},
{cdata (show (isNil (Cons (1, Nil))))},
{cdata (show (isNil (Cons ("A", Cons ("B", Nil)))))}
<p>{delist (Cons ("X", Cons ("Y", Cons ("Z", Nil))))}</p>
</body></html>
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