ormolu-0.8.1.1: data/examples/declaration/value/function/do-single-line-case-guards.hs

checkValue :: Int -> IO ()
checkValue n = do {putStr "Value is: "; case () of {_ | n < 0 -> putStrLn "negative" | n == 0 -> putStrLn "zero" | otherwise -> putStrLn "positive"}}