On 29 Jan 2009, at 16:10, beginners-request@haskell.org wrote:

Content-Type: text/plain; charset="iso-8859-1"

I didn't compile, but, by the looks of it, I would change

import qualified Data.ByteString as BS (readFile)

for

import qualified Data.ByteString.Lazy as BS (readFile)

as it seems sha1 needs a lazy bytestring

module Main where

import System.Environment (getArgs)

import Data.Digest.OpenSSL.MD5 (md5sum)

import Data.Digest.Pure.SHA (sha1, showDigest)

import qualified Data.ByteString.Lazy 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 now fails to compile with this error :

checksum.hs:17:22:

Couldn't match expected type `Data.ByteString.Internal.ByteString'

against inferred type `Data.ByteString.Lazy.Internal.ByteString'

In the expression: showDigest . sha1

In a case alternative: "sha1" -> showDigest . sha1

In the expression:

case codec of {

"md5" -> md5sum

"sha1" -> showDigest . sha1

_ -> error "Codec must be md5 or sha1 !" }

How can I both use md5sum and sha1 when one use a lazy ByteString end the other one does not ?

Thanks