hat-2.7.0.0: docs/BadInsort.hs
sort :: Ord a => [a] -> [a]
-- FAULT (1): missing equation for [] argument
sort (x:xs) = insert x (sort xs)
insert :: Ord a => a -> [a] -> [a]
insert x [] = [x]
insert x (y:ys) = if x <= y
-- FAULT (2): y missing from result
then x : ys
-- FAULT (3): recursive call is same
else y : insert x (y:ys)
main = putStrLn (sort "program")