[Haskell-cafe] iteratee enumHandle

Echo Nolan hellish at comcast.net
Thu Jul 9 22:49:14 EDT 2009

Hi Paolino.

What's happening is reading [Char] uses the Storable instance for Char 
which is 32-bit. Thus, you get gibberish. The below does what you want, 
by reading Word8s and converting them.

import Control.Exception
import Data.Char
import Data.Iteratee.IO
import Data.Iteratee.Base
import Data.Word
import System.IO

main :: IO ()
main = do
        h <- openFile "mamma23" ReadWriteMode
        hPutStr h "ciao"
        hSeek h AbsoluteSeek 0
        l <- enumHandle h readString >>= run
        print $ assert (l == "ciao") ()

-- This is declared on its own so I can give a type signature without making
-- any of the above lines unmanageably long.
readString :: IterateeG [] Word8 IO String
readString = joinI $ mapStream (chr . fromIntegral) stream2list

This only works for ASCII, of course. Someone should write some 
enumerators for the other encodings.

Echo Nolan

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