Hello, Thanks for the response On 04/04/2013 03:54 PM, David McBride wrote:
It just means you are trying to directly access a list element by its index in a list that doesn't have that many elements. It is probably somewhere in your floatData function, which you did not list. When you don't print it out to screen, haskell does not bother to evaluate it and therefore it never hits that error. If you didn't use that operator, then it is used in some library you are using.
I cleaned up the code layout and the error has now been replaced by another: f: <<loop>> The complete code (below) is pretty ugly. If anyone has a few minutes to look it over and suggest a source for the error that would be very helpful. Thanks, Roger import System.Environment -- For command line args import System.IO -- For, er, IO import System.Exit -- For early parole main = do cmdLineArgs -- Check only args <- getArgs let consts = args !! 1 let list = [] loadFile consts list -- Read file containing mol wts etc into 'list' let analytes = head list -- Names of analysed components (oxid, element...) let mw = floatData ( (processData list) !! 1 ) -- Weight (amu) of analyte let nox = floatData ( (processData list) !! 2 ) -- Oxygens in oxide formula let ncat = floatData ( (processData list) !! 3 ) -- Cations in oxide formula let units = floatData ( (processData list) !! 4 ) -- 1 = wt%; 1E4 = ppm let list = [] let fox = read (args !! 0) :: Float -- number of oxygens in f.u. let analyses = args !! 2 let outfile = args !! 3 loadFile analyses list -- Read file containing analyses into 'list' writeOutput analyses outfile list fox mw nox ncat units -- Write recalculated formulae into outfile mapM_ putStrLn list loadFile consts list = do inh <- openFile consts ReadMode list <- hGetContents inh hClose inh writeOutput infile outfile list fox mw nox ncat units = do inh <- openFile infile ReadMode -- the file of analyses, one per line outh <- openFile outfile WriteMode mainloop inh outh list fox mw nox ncat units hClose outh hClose inh -- the calculations are here mainloop inh outh list fox mw nox ncat units = do ineof <- hIsEOF inh if ineof then do print list -- For testing/debugging only return () else do inpStr <- hGetLine inh let list' = inpStr:list dat = floatData list' -- the analytical input data ta = zipWith (/) dat units -- convert all to wt% moles = zipWith (/) ta mw apo = zipWith (*) nox moles factor = fox/(sum apo) nanions= (map (* factor) apo) catox = zipWith (/) ncat nox ncat = zipWith (*) catox nanions hPutStr outh ( show ncat) mainloop inh outh list' fox mw nox ncat units cmdLineArgs = do args <- getArgs usage (length args) -- check 'em usage :: Int -> IO () usage nargs | nargs < 4 = fallOverAndDie "Usage: formula 'ox in formula' 'mol wt. file' 'analysis file' 'output file'." | otherwise = putStrLn "Input looks OK" fallOverAndDie :: String -> IO a fallOverAndDie err = do putStrLn err exitWith (ExitFailure 1) -- Convert the input numbers from strings to floats floatData :: [String] -> [Float] floatData inList = map read inList::[Float] -- Split input file into lines & words processData :: String -> [[String]] processData inpStr = do let thelines = lines inpStr let thewords = map words thelines thewords This is how I built the executable: ghc --make f.hs ghc --version The Glorious Glasgow Haskell Compilation System, version 7.6.1 This electronic communication is governed by the terms and conditions at http://www.mun.ca/cc/policies/electronic_communications_disclaimer_2012.php