Re: [Haskell-cafe] One liner?

"Paul Keir" writes:

module Main where

import System.Directory (getDirectoryContents)

main = do dc <- getDirectoryContents "./foo/" mapM_ putStrLn dc

mapM_ putStrLn (getDirectoryContents "./foo/")

Couldn't match expected type `[String]'

"mapM_ putStrLn" needs a "[String]" as an argument,

against inferred type `IO [FilePath]'

but you try to give it an "IO [FilePath]" (i.e. IO [String]). As you probably know, do-notation is syntactic sugar for the monad operators, and you can rewrite your function thusly: main = do dc <- getDirectoryContents "./foo/" mapM_ putStrLn dc => main = getDirectoryContents "./foo" >>= \dc -> mapM_ putStrLn dc => main = getDirectoryContents "./foo" >>= mapM_ putStrLn -k -- If I haven't seen further, it is by standing in the footprints of giants