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{-# OPTIONS_GHC -fwarn-incomplete-patterns -fwarn-overlapping-patterns #-}
module PMC006 where
len :: [a] -> Int
len xs = case xs of
[] -> 0
(_:ys) -> case () of
() | (_:_) <- xs -> 1 + len ys
-- -- we would like these to work too but they don't yet
--
-- len :: [a] -> Int
-- len [] = 0
-- len xs = case xs of
-- (_:ys) -> 1 + len ys
--
-- len :: [a] -> Int
-- len xs = case xs of
-- [] -> 0
-- ys -> case ys of
-- (_:zs) -> 1 + len zs
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