(...) Can someone tell me what's wrong with this? import qualified System.Posix.Directory as PD
readdirAll :: PD.DirStream -> IO [String] readdirAll d = do dir <- PD.readDirStream d if dir == "" then return [] else rest <- readdirAll d return (dir:rest) (...)
I don't know if this helps or disturbs, but I wrote a few different versions of your code as an exercise. If you want to try it, just uncomment the versions you want to check. The complete program below lists all files in current directory, using 'readdirAll' to get the full list. Best, Maurício module Main (Main.main) where import qualified System.Posix.Directory as PD import Data.List import Control.Monad main :: IO () readdirAll :: PD.DirStream -> IO [String] readdirAll ds = liftM reverse $ read [] where read ("":t) = return t read list = (PD.readDirStream ds) >>= glue where glue f = read (f:list) {- readdirAll ds = read where read = (PD.readDirStream ds) >>= rest rest "" = return [] rest h = liftM (h:) read -} {- readdirAll ds = do f <- PD.readDirStream ds rest f where rest "" = return [] rest h = return (h:) `ap` (readdirAll ds) -} main = (PD.openDirStream ".") >>= readdirAll >>= (putStrLn.show)