Hello I have the following snippet : ---------------------------------------------------------- module Main where import System.Environment (getArgs) import Data.Digest.OpenSSL.MD5 (md5sum) import Data.Digest.Pure.SHA (sha1, showDigest) import qualified Data.ByteString as BS (readFile) -- sha1 :: ByteString -> Digest -- readFile :: FilePath -> IO ByteString -- md5sum :: ByteString -> String -- showDigest :: Digest -> String checkHash :: String -> String -> String -> IO () checkHash codec hash file = let f = case codec of --"md5" -> md5sum "sha1" -> showDigest . sha1 _ -> error "Codec must be md5 or sha1 !" in BS.readFile file >>= \fileBS -> let fileHash = f fileBS in print (hash == fileHash) main = getArgs >>= \as -> case as of (codec:hash:file:_) -> checkHash codec hash file _ -> usage usage = print "checksum codec hash file" ---------------------------------------------------------- which fails to compile, this is the error I get : checksum.hs:20:19: Couldn't match expected type `Data.ByteString.Lazy.Internal.ByteString' against inferred type `Data.ByteString.Internal.ByteString' In the first argument of `f', namely `fileBS' In the expression: f fileBS In the definition of `fileHash': fileHash = f fileBS it looks like (showDigest . sha1) expects Data.ByteString.Lazy.Internal.ByteString but gets Data.ByteString.Internal.ByteString What can I do ? Thanks E. ----------------------------------------------------------------------------------------------- This e-mail (and any attachments) is confidential and may contain personal views which are not the views of Cimex Media Ltd and any affiliated companies, unless specifically stated. It is intended for the use of the individual or group to whom it is addressed. If you have received it in error, please delete it from your system, do not use, copy or disclose the information in any way nor act in reliance on it and please notify postmaster@cimex.com A company registered in England Wales. Company Number 03765711 Registered Office : The Olde Bakehouse, 156 Watling Street East, Towcester, Northants NN12 6DB This email was scanned by Postini, the leading provider in Managed Email Security.