see http://haskell.org/wiki/wiki?ThatAnnoyingIoType and http://haskell.org/wiki/wiki?UsingIo -- Hal Daume III "Computer science is no more about computers | hdaume@isi.edu than astronomy is about telescopes." -Dijkstra | www.isi.edu/~hdaume On Fri, 7 Jun 2002, Chris Moline wrote:
hi. i am really stuck on this problem and i cant seem to figure it out and so i am posting this in the hopes someone will help me. i realize you prolly get this kind of question alot but the wiki and the papers i have been reading arent helping to clarify things.
i am trying to write a little utility to make it easier to get rid of ports on my machine. the function that is giving me trouble is getDepends. it takes the name of a port and opens the appropriate +CONTENTS file and returns the dependencies it finds.
here is the function and its helper.
getDepends :: String -> [String] getDepends p = do handle <- openFile (portsDir ++ p) ReadMode fetchDepends handle
fetchDepends :: Handle -> [String] fetchDepends handle = do l <- hGetLine handle e <- hIsEOF handle case (not e) of -- ifs keep giving indent errors so ill just use case True -> case (matchRegex (mkRegex "^@pkgdep") l) of Just [a] -> [drop 8 l] ++ (fetchDepends handle) _ -> fetchDepends handle False -> ""
here is ghci's error messages.
Compiling Pheobe ( Phoebe.hs, interpreted )
Phoebe.hs:19: Couldn't match `[]' against `IO' Expected type: [t] Inferred type: IO Handle In the application `openFile (portsDir ++ p) ReadMode' In a 'do' expression pattern binding: handle <- openFile (portsDir ++ p) ReadMode
Phoebe.hs:24: Couldn't match `[]' against `IO' Expected type: [t] Inferred type: IO String In the application `hGetLine handle' In a 'do' expression pattern binding: l <- hGetLine handle Failed, modules loaded: none.
could someone be so kind as to explain what the problem is?
sincerly, chris moline _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe