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-- !!! Newtypes
-- A variation of tc014 that Sigbjorn said failed
module Main where
data Expr a b = One a | Many [b]
newtype Pat a = InP (Expr a (Pat a), Int)
newtype PExpr a = InPE (Expr a (PExpr a), Int)
plus1 x@(InPE (_, loc)) = InPE (Many [x], loc)
one x l = InPE (One (plus1 x), l)
outP (InP x) = x
getPatNames p
= case outP p of
(One n, _) -> [n]
(Many ps, _) -> concatMap getPatNames ps
main = print (take 10 (map getPatNames (repeat (InP (One "n", 1)))))
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